Dissertations / Theses on the topic 'Numerical weather forecasting Australia'
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1
Yan, Hanjun. "Numerical methods for data assimilation in weather forecasting." HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/555.
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Data assimilation plays an important role in weather forecasting. The purpose of data assimilation is try to provide a more accurate atmospheric state for future forecast. Several existed methods currently used in this field fall into two categories: statistical data assimilation and variational data assimilation. This thesis focuses mainly on variational data assimilation. The original objective function of three dimensional data assimilation (3D-VAR) consists of two terms: the difference between the pervious forecast and analysis and the difference between the observations and analysis in observation space. Considering the inaccuracy of previous forecasting results, we replace the first term by the difference between the previous forecast gradients and analysis gradients. The associated data fitting term can be interpreted using the second-order finite difference matrix as the inverse of the background error covariance matrix in the 3D-VAR setting. In our approach, it is not necessary to estimate the background error covariance matrix and to deal with its inverse in the 3D-VAR algorithm. Indeed, the existence and uniqueness of the analysis solution of the proposed objective function are already established. Instead, the solution can be calculated using the conjugate gradient method iteratively. We present the experimental results based on WRF simulations. We show that the performance of this forecast gradient based DA model is better than that of 3D-VAR. Next, we propose another optimization method of variational data assimilation. Using the tensor completion in the cost function for the analysis, we replace the second term in the 3D-VAR cost function. This model is motivated by a small number of observations compared with the large portion of the grids. Applying the alternating direction method of multipliers to solve this optimization problem, we conduct numerical experiments on real data. The results show that this tensor completion based DA model is competitive in terms of prediction accuracy with 3D-VAR and the forecast gradient based DA model. Then, 3D-VAR and the two model proposed above lack temporal information, we construct a third model in four-dimensional space. To include temporal information, this model is based on the second proposed model, in which introduce the total variation to describe the change of atmospheric state. To this end, we use the alternating direction method of multipliers. One set of experimental results generates a positive performance. In fact, the prediction accuracy of our third model is better than that of 3D-VAR, the forecast gradient based DA model, and the tensor completion based DA model. Nevertheless, although the other sets of experimental results show that this model has a better performance than 3D-VAR and the forecast gradient based DA model, its prediction accuracy is slightly lower than the tensor completion based model.
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Torrisi, Lucio. "The numerical weather prediction system at the Italian Air Force Weather Service : impact of non-conventional observations and increased resolution /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FTorrisi.pdf.
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Ancell, Brian C. "The nature of adjoint sensitivities with respect to model parameters and their use in adaptive data assimilation /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10042.
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Cordy, Paul David. "Applied automated numerical avalanche forecasting using electronic weather sensor data." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32241.
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Numerical avalanche prediction was used for Canadian highways avalanche
forecasting for ten years before changes in information technology infrastructure
rendered the original numerical avalanche forecasting model incompatible and therefore
obsolete. Now these efforts are being renewed with greater automation by the use of
electronic weather sensor data. Use of this data presents several challenges and
opportunities. Automated hourly observations generate large datasets that require
systems for filtering historic and current data; as well as fitness testing routines that
dynamically extract independent validation samples from serially correlated datasets.
These weather sensor data manipulation systems offer several advantages over traditional
avalanche prediction models that are based on manually observed weather and surface
snow information. Rapid dataset generation enables spatial scaling of predictions, easy
generation and testing of memory variables, model comparison, and visual verification of
predicted avalanche probability time series. These features will facilitate operational
implementation of avalanche forecasting models for applied computer assisted avalanche
forecasting-in highways avalanche control programs across British Columbia, Canada.
In the winter of 2006/7, the Avalanche Forecast System (AFS) was applied in two
avalanche prone transportation corridors. The AFS uses only electronic weather sensor
data and incorporates all of the aforementioned capabilities. A nearest neighbour
analysis is used to generate avalanche probabilities, however the AFS data management
systems could also be made to operate with classical linear and modern non-linear
statistical prediction methods. Automated filters eliminate erroneous data dynamically,
permit investigation of various prediction targets (such as natural avalanche occurrences,
or avalanches of different size classes), and a jackknife cross-validation routine generates
fitness statistics by selecting test cases that are not temporally autocorrelated. The AFS
was applied operationally in Kootenay Pass, near Salmo, BC, and also at Bear Pass, near
Stewart, BC, where accuracy of 76% +/-2% and 71% +/-2% were achieved respectively.Arts, Faculty of
Geography, Department of
Graduate
5
Lawless, Amos S. "Development of linear models for data assimilation in numerical weather prediction." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365423.
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Bilodeau, Bernard. "Accuracy of a truncated barotropic spectral model : numerical versus analytical solutions." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66037.
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Xue, Ming. "A nonhydrostatic numerical model in sigma-coordinates and simulations of mesoscale phenomena." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328942.
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Ramamurthy, Mohan K. "Four dimensional data assimilation in a limited area model for the monsoon region /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1986.
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Wahl, Sabrina [Verfasser]. "Uncertainty in mesoscale numerical weather prediction: probabilistic forecasting of precipitation / Sabrina Wahl." Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1080561099/34.
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Vetra-Carvalho, Sanita. "Properties of the ensemble Kalman filter for convective-scale numerical weather forecasting." Thesis, University of Reading, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590111.
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Atmospheric data assimilation has now started to deal with high model resolution scales of O(lkm) where dynamical properties of the atmosphere exploited in larger scale models may no longer be valid. This leads to a problem in high-resolution data assimilation systems since balances such as the hydrostatic balance are still used to model forecast errors. From scale analysis arguments we recognise that such balances do not necessarily need to be valid at small scales and in this work we use the convective scale Met Office Global and Regional Ensemble Prediction System (MOGREPS) to show that indeed the hydrostatic balance at a horizontal resolution of 1.5 km ceases to be valid in the ensemble perturbations in regions where convection is present while it is valid in regions with no convection. We show that the horizontal threshold at which the hydrostatic balance becomes valid as a vertical average in the ensemble perturbations regardless of the presence of convection is 22 km. We also make use of ensemble methods to establish their applicability (0 convective scale models. In particular we apply (he ensemble square root filter (EnSRF) to a one-dimensional idealised column model wilh a parameterized cloud scheme and a discontinuous rain scheme. We show that the ensemble filter can caprure the true solution within a linear ('No cloud') model regime and non-linear ('Cloud') regime; however, if many good quality observations are used the ensemble fails to capture the true solution within the discontinuous CRain') regime. Interestingly, this can be alleviated if only a portion of the state space is observed. Moreover, having fewer spatial observations also improves the ensemble estimate for the ~mperature in the 'Rain' regime, while the estimate of state variables is slightly degraded in the 'No cloud' and 'Cloud' regimes.
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Liu, Jia. "Rainfall-runoff modelling and numerical weather prediction for real-time flood forecasting." Thesis, University of Bristol, 2011. http://hdl.handle.net/1983/87375e5e-4186-4707-b7c6-465617dc1ac1.
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This thesis focuses on integrating rainfall-runoff modelling with a mesoscale numerical weather prediction (NWP) model to make real-time flood forecasts at the catchment scale. Studies carried out are based on catchments in Southwest England with a main focus on the Brue catchment of an area of 135 km2 and covered by a dense network of 49 rain gauges and a C-band weather radar. The studies are composed of three main parts: Firstly, two data mining issues are investigated to enable a better calibrated rainfall-runoff model for flood forecasting. The Probability Distributed Model (PDM) is chosen which is widely used in the UK. One of the issues is the selection of appropriate data for model calibration regarding the data length and duration. It is found that the information quality of the calibration data is more important than the data length in determining the model performance after calibration. An index named the Information Cost Function (ICF) developed on the discrete wavelet decomposition is found to be efficient in identifying the most appropriate calibration data scenario. Another issue is for the impact of the temporal resolution of the model input data when using the rainfall-runoff model for real-time forecasting. Through case studies and spectral analyses, the optimal choice of the data time interval is found to have a positive relation with the forecast lead time, i.e., the longer is the lead time, the larger should the time interval be. This positive relation is also found to be more obvious in the catchment with a longer concentration time. A hypothetical curve is finally concluded to describe the general impact of data time interval in real-time forecasting. The development of the NWP model together with the weather radar allows rainfall forecasts to be made in high resolutions of time and space. In the second part of studies, numerical experiments for improving the NWP rainfall forecasts are carried out based on the newest generation mesoscale NWP model, the Weather Research & Forecasting (WRF) model. The sensitivity of the WRF performance is firstly investigated for different domain configurations and various storm types regarding the evenness of rainfall distribution in time and space. Meanwhile a two-dimensional verification scheme is developed to quantitatively evaluate the WRF performance in the temporal and spatial dimensions. Following that the WRF model is run in the cycling mode in tandem with the three-dimensional variational assimilation technique for continuous assimilation of the radar reflectivity and traditional surface/ upperair observations. The WRF model has shown its best performance in producing both rainfall simulations and improved rainfall forecasts through data assimilation for the storm events with two dimensional evenness of rainfall distribution; while for highly convective storms with rainfall concentrated in a small area and a short time period, the results are not ideal and much work remains to be done in the future. Finally, the rainfall-runoff model PDM and the rainfall forecasting results from WRF are integrated together with a real-time updating scheme, the Auto-Regressive and Moving Average (ARMA) model to constitute a flood forecasting system. The system is tested to be reliable in the small catchment such as Brue and the use of the NWP rainfall products has shown its advantages for long lead-time forecasting beyond the catchment concentration time. Keywords: rainfall-runoff modelling, numerical weather prediction, flood forecasting, real-time updating, spectral analysis, data assimilation, weather radar.
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Batt, Kenneth Leslie School of Mathematics UNSW. "The observation and modelling of winds over South Eastern Australia." Awarded by:University of New South Wales. School of Mathematics, 2004. http://handle.unsw.edu.au/1959.4/23472.
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This study uses a very high resolution numerical weather prediction (NWP) model to investigate the complex structure and behaviour of cold fronts along the New South Wales coast during the warmer months of the year, the complex interaction between the wind flow and coastlines and elevated areas as well as the lee-trough effect, particularly the way it affects waters off the east coast of Tasmania, The study also investigates the utility of the higher resolution NWP model to better predict wind fields compared to a lower resolution model. The University of New South Wales very high resolution model (HIRES), nested in the Australian Bureau of Meteorology's coarse NWP model (GASP), was run at various horizontal resolutions (from 15 to 25km) in order to investigate the above-mentioned features. It was found to bave very good skill in resolving the features and was also found to be very accurate in the prediction of surface wind fields for various yacht race events out to at least four days ahead. It can be concluded that there is considerable skill in the ability of high-resolution NWP models such as HIRES, to predict the major features of the wind fields over the ocean out to several days ahead. Moreover, it was also able to more accurately simulate the complex structure of the summer-time cool change as it progressed along the NSW coast than the lower resolution model runs. The influence of coastlines, particularly ones with complex topographical features, on the wind flow was demonstrated to a limited extent throughout the study. Finally the following concepts were also verified as a result of the study: - air flow takes the path of least resistance - the shape of topography can help generate local turbulence - the orientation of the wind flow to a mountain range is important in determining turbulent effects. - under certain airflow and stability situations, standing wave activity and a lee trough can be observed in the lee of mountains, hills or even high coastal cliffs.
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Roch, Michel. "L'impact de l'assimilation directe de taux de précipitation satellitaires dans un modèle météorologique." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66080.
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Moatshe, Peggy Seanokeng. "Verification of South African Weather Service operational seasonal forecasts." Pretoria: [S.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-08112009-131703.
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Cutler, Nicholas Jeffrey Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Characterising the uncertainty in potential large rapid changes in wind power generation." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2009. http://handle.unsw.edu.au/1959.4/43570.
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Wind energy forecasting can facilitate wind energy integration into a power system. In particular, the management of power system security would benefit from forecast information on plausible large, rapid change in wind power generation. Numerical Weather Prediction (NWP) systems are presently the best available tools for wind energy forecasting for projection times between 3 and 48 hours. In this thesis, the types of weather phenomena that cause large, rapid changes in wind power in southeast Australia are classified using observations from three wind farms. The results show that the majority of events are due to horizontal propagation of spatial weather features. A study of NWP systems reveals that they are generally good at forecasting the broad large-scale weather phenomena but may misplace their location relative to the physical world. Errors may result from developing single time-series forecasts from a single NWP grid point, or from a single interpolation of proximate grid points. This thesis presents a new approach that displays NWP wind forecast information from a field of multiple grid points around the wind farm location. Displaying the NWP wind speeds at the multiple grid points directly would potentially be misleading as they each reflect the estimated local surface roughness and terrain at a particular grid point. Thus, a methodology was developed to convert the NWP wind speeds at the multiple grid points to values that reflect surface conditions at the wind farm site. The conversion method is evaluated with encouraging results by visual inspection and by comparing with an NWP ensemble. The multiple grid point information can also be used to improve downscaling results by filtering out data where there is a large chance of a discrepancy between an NWP time-series forecast and observations. The converted wind speeds at multiple grid points can be downscaled to site-equivalent wind speeds and transformed to wind farm power assuming unconstrained wind farm operation at one or more wind farm sites. This provides a visual decision support tool that can help a forecast user assess the possibility of large, rapid changes in wind power from one or more wind farms.
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Tenna, Alyce. "An evaluation of the weather research and forecasting model's ability in simulating fire weather for the Southwest of Western Australia." Thesis, Tenna, Alyce (2016) An evaluation of the weather research and forecasting model's ability in simulating fire weather for the Southwest of Western Australia. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/35249/.
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The southwest of Western Australia (SWWA) is prone to bushfires, and these have significant social, environmental and economic impacts. One of the major influences on fire weather is climate, and it is therefore important to understand current and future changes in fire weather in relation to climate change. Global climate models (GCMs) can be used to investigate current and future changes in fire weather, however, their coarse resolution (100 to 250 km) limits their applicability at the regional scale. Regional climate models (RCMs) are used to dynamically downscale GCMs to a regional scale (1 to 10 km). This study evaluates a RCM, the Weather Research and Forecast Model (WRF), in its ability to simulate fire weather over the period 1981 to 2010 in the SWWA . Fire weather was quantified using the McArthur Forest Fire Danger Index (FFDI), which is the current operational index used for fire danger warnings in Australia. FFDI was computed from both WRF and observational data, and results show that WRF captured the observed FFDI trend, albeit with a slight overestimation. Errors in WRF derived FFDI were mainly caused by WRF’s underestimation of relative humidity, which caused the FFDI to be overestimated, particularly along coastal regions. Fire Danger Ratings (FDRs), which are fire risk categories derived from the FFDI, were also examined, and it was shown that WRF was able to simulate low-risk FDRs with greater skill in comparison to high-risk FDRs. Although WRF performed poorly in simulating high-risk FDRs, these categories are a rare and unusual occurrence of the upper-distribution, and the majority of the FFDI distribution was well-represented by WRF. This study shows that overall, WRF was a useful tool for simulating fire weather over the SWWA.
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Smith, Robert K. "The contour-advective semi-Lagrangian hybrid algorithm approach to weather forecasting and freely propagating inertia-gravity waves in the shallow-water system." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/716.
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Torn, Ryan. "Using ensemble data assimilation for predictability and dynamics /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10037.
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Marx, Hester Gerbrecht. "The use of artificial neural networks to enhance numerical weather prediction model forecasts of temperature and rainfall." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-02102009-161401/.
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Devlin, David J. J. "An investigation into the use of balance in operational numerical weather prediction." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1903.
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Presented in this study is a wide-ranging investigation into the use of properties of balance in an operational numerical weather prediction context. Initially, a joint numerical and observational study is undertaken. We used the Unified Model (UM), the suite of atmospheric and oceanic prediction software used at the UK Met Office (UKMO), to locate symmetric instabilities (SIs), an indicator of imbalanced motion. These are areas of negative Ertel potential vorticity (in the Northern hemisphere) calculated on surfaces of constant potential temperature. Once located, the SIs were compared with satellite and aircraft observational data. As a full three-dimensional calculation of Ertel PV proved outwith the scope of this study we calculated the two-dimensional, vertical component of the absolute vorticity, to assess the inertial stability criterion. We found that at the synoptic scale in the atmosphere, if there existed a symmetric instability, it was dominated by an inertial instability. With the appropriate observational data, evidence of inertial instability from the vertical component of the absolute vorticity, predicted by the UM was found at 12km horizontal grid resolution. Varying the horizontal grid resolution allowed the estimation of a grid length scale, above which, the inertial instability was not captured by the observational data, of approximately 20km. Independently, aircraft data was used to estimate that horizontal grid resolutions above 20-25km should not model any features of imbalance providing a real world estimate of the lower bound of the grid resolution that should be employed by a balanced atmospheric prediction model. A further investigation of the UM concluded that the data assimilation scheme and time of initialisation had no effect on the generation of SIs. An investigation was then made into the robustness of balanced models in the shallow water context, employing the contour-advective semi-Lagrangian (CASL) algorithm, Dritschel & Ambaum (1997), a novel numerical algorithm that exploits the underlying balance observed within a geophysical flow at leading order. Initially two algorithms were considered, which differed by the prognostic variables employed. Each algorithm had their three-time-level semi-implicit time integration scheme de-centred to mirror the time integration scheme of the UM. We found that the version with potential vorticity (PV), divergence and acceleration divergence, CA[subscript(δ,γ)], as prognostic variables preserved the Bolin-Charney balance to a much greater degree than the model with PV, divergence and depth anomaly CA[subscript(tilde{h},δ)], as prognostic variables. This demonstrated that CA[subscript(δ,γ)] was better equipped to benefit from de-centring, an essential property of any operational numerical weather prediction (NWP) model. We then investigate the robustness of CA[subscript(δ,γ)] by simulating flows with Rossby and Froude number O(1), to find the operational limits of the algorithm. We also investigated increasing the efficiency of CA[subscript(δ,γ)] by increasing the time-step Δt employed while decreasing specific convergence criteria of the algorithm while preserving accuracy. We find that significant efficiency gains are possible for predominantly mid-latitude flows, a necessary step for the use of CA[subscript(δ,γ)] in an operational NWP context. The study is concluded by employing CASL in the non-hydrostatic context under the Boussinesq approximation, which allows weak stratification to be considered, a step closer to physical reality than the shallow water case. CASL is compared to the primitive equation pseudospectral (PEPS) and vorticity-based pseudospectral (VPS) algorithms, both as the names suggest, spectral-based algorithms, which again differ by the prognostic variables employed. This comparison is drawn to highlight the computational advantages that CASL has over common numerical methods used in many operational forecast centres. We find that CASL requires significantly less artificial numerical diffusion than its pseudospectral counterparts in simulations of Rossby number ~O(1). Consequently, CASL obtains a much less diffuse, more accurate solution, at a lower resolution and therefore lower computational cost. At low Rossby number, where the flow is strongly influence by the Earth's rotation, it is found that CASL is the most cost-effective method. In addition, CASL also preserves a much greater proportion of balance, diagnosed with nonlinear quasigeostrophic balance (NQG), another significant advantage over its pseudospectral counterparts.
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Martínez-Arellano, G. "Forecasting wind power for the day-ahead market using numerical weather prediction models and computational intelligence techniques." Thesis, Nottingham Trent University, 2015. http://irep.ntu.ac.uk/id/eprint/322/.
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Wind power forecasting is essential for the integration of large amounts of wind power into the electric grid, especially during large rapid changes of wind generation. These changes, known as ramp events, may cause instability in the power grid. Therefore, detailed information of future ramp events could potentially improve the backup allocation process during the Day Ahead (DA) market (12 to 36 hours before the actual operation), allowing the reduction of resources needed, costs and environmental impact. It is well established in the literature that meteorological models are necessary when forecasting more than six hours into the future. Most state-of-the-art forecasting tools use a combination of Numerical Weather Prediction (NWP) forecasts and observations to estimate the power output of a single wind turbine or a whole wind farm. Although NWP systems can model meteorological processes that are related to large changes in wind power, these might be misplaced i.e. in the wrong physical position. A standard way to quantify such errors is by the use of NWP ensembles. However, these are computationally expensive. Here, an alternative is to use spatial fields, which are used to explore different numerical grid points to quantify variability. This strategy can achieve comparable results to typical numerical ensembles, which makes it a potential candidate for ramp characterisation. A major disadvantage of most ramp events studies is that they are based on a binary classification, which specifies a percentage of change in power within a defined time window. This may produce artifacts, as ramp detection tools might miss potential changes due to errors in the forecasts. Moreover, a change just below the threshold could be equally damaging as a change that meets the definition. The novel contribution of this project is the application of computational intelligence techniques for wind power forecasting and ramp event characterisation. To achieve this, two stages are required. In the first stage, Genetic Programming (GP) is used to generate an ensemble of wind power forecasts based on the idea of spatial fields. This in its own is an important contribution as the approach will allow the development of computationally cheap wind speed-to-power conversion models, without making any assumptions of their shape or properties. In the second stage, wind power forecasts are converted into a set of filtered signals in order to study ramp events at different time scales. These signals, when applied to a set of Fuzzy Logic rules, indicate the probabilities of a ramp event happening, avoiding the binary classification, which is another important contribution of this work. The observation data used for this investigation was obtained from a real wind park in Galicia, Spain and some observation points in Illinois, USA. The numerical data was obtained by running locally a Mesoscale model. Experiments showed that the accuracy of wind power forecasts obtained using GP as a downscaling/conversion method are comparable to traditional forecasting tools as it is able to achieve an 87% of accuracy. At the same time the computational effort was significantly reduced. The novel ramp detection approach that is introduced here, is able to outperform a basic binary-based detection algorithm. In addition, the fuzzy rules can provide a probability of other events happening; events that might not meet the crisp definition. Using colour maps, which are easier to interpret by human non-experts, it is possible to show how an event is developing in different time windows. Finally, it is shown how neighbouring points can help modelling events that might not be detected using only the closest point of the grid. Having a detailed characterisation of future ramp events can help grid operators to make more informed decisions on the scheduling of back-up units needed and hence to potentially reduce costs and the environmental impact.
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Wahl, Douglas Timothy. "Increasing range and lethality of Extended -Range Munitions (ERMS) using Numerical Weather Prediction (NWP) and the AUV workbench to compute a Ballistic Correction (BALCOR)." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FWahl.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Wendell Nuss, Don Brutzmann. "December 2006." Includes bibliographical references (p. 107-116). Also available in print.
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Gerard, Luc. "Physical parameterisations for a high resolution operational numerical weather prediction model." Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211550.
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Les modèles de prévision opérationnelle du temps résolvent numériquement les équations de la mécanique des fluides en calculant l'évolution de champs (pression, température, humidité, vitesses) définis comme moyennes horizontales à l'échelle des mailles d'une grille (et à différents niveaux verticaux).Les processus d'échelle inférieure à la maille jouent néanmoins un rôle essentiel dans les transferts et les bilans de chaleur, humidité et quantité de mouvement. Les paramétrisations physiques visent à évaluer les termes de source correspondant à ces phénomènes, et apparaissant dans les équations des champs moyens aux points de grille.
Lorsque l'on diminue la taille des mailles afin de représenter plus finement l'évolution des phénomènes atmosphériques, certaines hypothèses utilisées dans ces paramétrisations perdent leur validité. Le problème se pose surtout quand la taille des mailles passe en dessous d'une dizaine de kilomètres, se rapprochant de la taille des grands systèmes de nuages convectifs (systèmes orageux, lignes de grain).
Ce travail s'inscrit dans le cadre des développements du modèle à mailles fines ARPÈGE ALADIN, utilisé par une douzaine de pays pour l'élaboration de prévisions à courte échéance (jusque 48 heures).
Nous décrivons d'abord l'ensemble des paramétrisations physiques du modèle.
Suit une analyse détaillée de la paramétrisation actuelle de la convection profonde. Nous présentons également notre contribution personnelle à celle ci, concernant l'entraînement de la quantité de mouvement horizontale dans le nuage convectif.
Nous faisons ressortir les principaux points faibles ou hypothèses nécessitant des mailles de grandes dimensions, et dégageons les voies pour de nouveaux développements.
Nous approfondissons ensuite deux des aspects sortis de cette discussion: l'usage de variables pronostiques de l'activité convective, et la prise en compte de différences entre l'environnement immédiat du nuage et les valeurs des champs à grande échelle. Ceci nous conduit à la réalisation et la mise en œuvre d'un schéma pronostique de la convection profonde.
A ce schéma devraient encore s'ajouter une paramétrisation pronostique des phases condensées suspendues (actuellement en cours de développement par d'autres personnes) et quelques autres améliorations que nous proposons.
Des tests de validation et de comportement du schéma pronostique ont été effectués en modèle à aire limitée à différentes résolutions et en modèle global. Dans ce dernier cas l'effet du nouveau schéma sur les bilans globaux est également examiné.
Ces expériences apportent un éclairage supplémentaire sur le comportement du schéma convectif et les problèmes de partage entre la schéma de convection profonde et le schéma de précipitation de grande échelle.
La présente étude fait donc le point sur le statut actuel des différentes paramétrisations du modèle, et propose des solutions pratiques pour améliorer la qualité de la représentation des phénomènes convectifs.
L'utilisation de mailles plus petites que 5 km nécessite enfin de lever l'hypothèse hydrostatique dans les équations de grande échelle, et nous esquissons les raffinements supplémentaires de la paramétrisation possibles dans ce cas.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
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Yu, Wansik. "Ensemble Flood Forecasting using High-Resolution Ensemble Numerical Weather Prediction with Radar Based Prediction Considering Rainfall Forecast Uncertainty." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192164.
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Shepherd, Tristan James. "A Numerical Modelling Study of Tropical Cyclone Sidr (2007): Sensitivity Experiments Using the Weather Research and Forecasting (WRF) Model." Thesis, University of Canterbury. Geography, 2008. http://hdl.handle.net/10092/2611.
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The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters. Their majesty evolves from the significant range of spatial scales they operate over: from the mesoscale, to the larger synoptic-scale. Their associated violent winds and seas, however, are often the cause of damage and destruction for settlements in their path. Between 10/11/07 and 16/11/07, tropical cyclone Sidr formed and intensified into a category 5 hurricane over the southeast tropical waters of the northern Indian Ocean. Sidr tracked west, then north, during the course of its life, and eventually made landfall on 15/11/07, as a category 4 cyclone near the settlement of Barguna, Bangladesh. The storm affected approximately 2.7 million people in Bangladesh, and of that number 4234 were killed. In this study, the dynamics of tropical cyclone Sidr are simulated using version 2.2.1 of Advanced Weather Research and Forecasting — a non-hydrostatic, two-way interactive, triply-nested-grid mesoscale model. Three experiments were developed examining model sensitivity to ocean-atmosphere interaction; initialisation time; and choice of convective parameterisation scheme. All experiments were verified against analysed synoptic data. The ocean-atmosphere experiment involved one simulation of a cold sea surface temperature, fixed at 10 °C; and simulated using a 15 km grid resolution. The initialisation experiment involved three simulations of different model start time: 108-, 72-, and 48-hours before landfall respectively. These were simulated using a 15 km grid resolution. The convective experiment consisted of four simulations, with three of these using a different implicit convective scheme. The three schemes used were, the Kain-Fritsch, Betts-Miller-Janjic, and Grell-Devenyi ensemble. The fourth case simulated convection explicitly. A nested domain of 5km grid spacing was used in the convective experiment, for high resolution modelling. In all experiments, the Eta-Ferrier microphysics scheme, and the Mellor-Yamada-Janjic planetary boundary layer scheme were used. As verified against available observations, the model showed considerable sensitivity in each of the experiments. The model was found to be well suited for combining ocean-atmosphere interactions: a cool sea surface caused cyclone Sidr to dissipate within 24 hours. The initialisation simulations indicated moderate model sensitivity to initialisation time: variations were found for both cyclone track and intensity. Of the three simulations, an initialisation time 108 hours prior to landfall, was found to most accurately represent cyclone Sidr’s track and intensity. Finally, the convective simulations showed that considerable differences were found in cyclone track, intensity, and structure, when using different convective schemes. The Kain-Fritsch scheme produced the most accurate cyclone track and structure, but the rainfall rate was spurious on the sub-grid-scale. The Betts-Miller-Janjic scheme resolved realistic rainfall on both domains, but cyclone intensity was poor. Of particular significance, was that explicit convection produced a similar result to the Grell-Devenyi ensemble for both model domain resolutions. Overall, the results suggest that the modelled cyclone is highly sensitive to changes in initial conditions. In particular, in the context of other studies, it appears that the combination of convective scheme, microphysics scheme, and boundary layer scheme, are most significant for accurate track and intensity prediction.
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Hoyos, Carlos D. "Intraseasonal Variability: Processes, Predictability and Prospects for Prediction." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04102006-135125/.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2006.Dr. Peter J. Webster, Committee Chair ; Dr. Judith A. Curry, Committee Member ; Dr. Robert Dickinson, Committee Member ; Dr. Robert X. Black, Committee Member ; Dr. Predrag Cvitanovic, Committee Member.
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Khajehei, Sepideh. "A Multivariate Modeling Approach for Generating Ensemble Climatology Forcing for Hydrologic Applications." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2403.
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Reliability and accuracy of the forcing data plays a vital role in the Hydrological Streamflow Prediction. Reliability of the forcing data leads to accurate predictions and ultimately reduction of uncertainty. Currently, Numerical Weather Prediction (NWP) models are developing ensemble forecasts for various temporal and spatial scales. However, it is proven that the raw products of the NWP models may be biased at the basin scale; unlike model grid scale, depending on the size of the catchment. Due to the large space-time variability of precipitation, bias-correcting the ensemble forecasts has proven to be a challenging task. In recent years, Ensemble Pre-Processing (EPP), a statistical approach, has proven to be helpful in reduction of bias and generation of reliable forecast. The procedure is based on the bivariate probability distribution between observation and single-value precipitation forecasts. In the current work, we have applied and evaluated a Bayesian approach, based on the Copula density functions, to develop an ensemble precipitation forecasts from the conditional distribution of the single-value precipitation. Copula functions are the multivariate joint distribution of univariate marginal distributions and are capable of modeling the joint distribution of two variables with any level of correlation and dependency. The advantage of using Copulas, amongst others, includes its capability of modeling the joint distribution independent of the type of marginal distribution. In the present study, we have evaluated the capability of copula-based functions in EPP and comparison is made against an existing and commonly used procedure for same i.e. meta-Gaussian distribution. Monthly precipitation forecast from Climate Forecast System (CFS) and gridded observation from Parameter-elevation Relationships on Independent Slopes Model (PRISM) have been utilized to create ensemble pre-processed precipitation over three sub-basins in the western USA at 0.5-degree spatial resolution. The comparison has been made using both deterministic and probabilistic frameworks of evaluation. Across all the sub-basins and evaluation techniques, copula-based technique shows more reliability and robustness as compared to the meta-Gaussian approach.
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Lopes, Francisco Manuel Tavares. "Short-term forecasting for direct normal irradiance with numerical weather prediction models in Alentejo (Southern Portugal): implications for concentration solar energy technologies." Doctoral thesis, Universidade de Évora, 2020. http://hdl.handle.net/10174/28724.
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With the potential to sustain the world’s energy needs, solar energy plays a major role for the renewable
energy transition. However, inherent problems exist in solar energy forecasting, a very important tool for
power plant operators that allows an efficient energy management and dispatch operations in the electric
grid. In particular, concentrating solar power (CSP) systems, which rely on direct normal irradiance (DNI)
and its high variability, which links uncertainty to the electrical energy outputs of CSP plants. The main
atmospheric factors that influence DNI variation at surface are clouds and aerosols, which are misrepresented
by current numerical weather prediction models. To provide accurate predictions of DNI for efficient CSP
operations, particularly during periods of direct solar intermittency, the solar resource needs to be well
characterized. Solution to this problem is still one of today’s challenges in solar forecasting. This thesis
makes use of short-term forecasts of DNI from the Integrated Forecasting System (IFS), the global model
of the European Centre for Medium-Range Weather Forecasts (ECMWF), together with ground-based
measurements in Alentejo region (southern Portugal). The evaluation of the solar resource in the region is
based on the IFS predictions, as well as the prediction of energy production outputs from different CSP
systems through the System Advisor Model (SAM) power plant simulator, in which the results are compared
with local measured data. To improve the role that DNI forecasting has in CSP power plants, several
post-processing techniques are used for the correction of hour and day-ahead values of DNI. Different
operational strategies are discussed and proposed according to the obtained results; Resumo:
Previsão de Curto Tempo de Radiação Normal Directa Através de
Modelos Numéricos de Previsão do Tempo no Alentejo (Sul de
Portugal): Implicações para as Tecnologias de Concentração Solar
Com potencial para assegurar as necessidades energéticas do mundo, a energia solar desempenha um
papel importante na transição energética renovável. Contudo, existem problemas inerentes na previsão de
energia solar, uma ferramenta muito importante para os operadores de centrais eléctricas que permite uma
gestão energética mais eficiente e operações de distribuição da mesma na rede eléctrica. Em particular, os
sistemas de concentração de energia solar (CSP), que dependem da radiação normal directa (DNI) e da sua
elevada variabilidade, atribuindo incerteza à geração de energia eléctrica resultantes de centrais CSP. Para
fornecer previsões precisas para operações CSP eficientes, particularmente durante períodos de intermitência
solar directa, o DNI precisa de ser bem caracterizado. Os principais factores atmosféricos que influenciam a
variação de DNI à superfície são as nuvens e os aerossóis, que não são representados realisticamente pelos
actuais modelos numéricos de previsão do tempo. A solução para este problema é ainda hoje em dia um
desafio em previsão solar. Esta tese faz uso das previsões de curto-período de DNI do Integrated Forecasting
System (IFS), modelo global do European Centre for Medium-Range Weather Forecasts (ECMWF), em
conjunto com medidas à superfície na região do Alentejo (sul de Portugal). A avaliação do recurso solar na
região é efectuada com base em previsões do IFS, tal como a previsão de outputs de produção energética
de diferentes sistemas CSP através do simulador de centrais eléctricas System Advisor Model (SAM), onde
os resultados são comparados com os obtidos com medidas meteorológicas locais. Para melhorar o papel
que a previsão de DNI tem em centrais CSP, várias técnicas de pós-processamento são efectuadas para a
correção de valores de DNI para a hora e dia seguinte. Diferentes estratégias de operação são discutidas e
propostas de acordo com resultados obtidos.
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Dixon, Glen W. "Modelling the statistical behaviour of temperature using a modified Brennan and Schwarts (1982) interest rate model /." [St. Lucia, Qld], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18235.pdf.
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Thornes, Tobias. "Investigating the potential for improving the accuracy of weather and climate forecasts by varying numerical precision in computer models." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:038874a3-710a-476d-a9f7-e94ef1036648.
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Accurate forecasts of weather and climate will become increasingly important as the world adapts to anthropogenic climatic change. Forecasts' accuracy is limited by the computer power available to forecast centres, which determines the maximum resolution, ensemble size and complexity of atmospheric models. Furthermore, faster supercomputers are increasingly energy-hungry and unaffordable to run. In this thesis, a new means of making computer simulations more efficient is presented that could lead to more accurate forecasts without increasing computational costs. This 'scale-selective reduced precision' technique builds on previous work that shows that weather models can be run with almost all real numbers represented in 32 bit precision or lower without any impact on forecast accuracy, challenging the paradigm that 64 bits of numerical precision are necessary for sufficiently accurate computations. The observational and model errors inherent in weather and climate simulations, combined with the sensitive dependence on initial conditions of the atmosphere and atmospheric models, renders such high precision unnecessary, especially at small scales. The 'scale-selective' technique introduced here therefore represents smaller, less influential scales of motion with less precision. Experiments are described in which reduced precision is emulated on conventional hardware and applied to three models of increasing complexity. In a three-scale extension of the Lorenz '96 toy model, it is demonstrated that high resolution scale-dependent precision forecasts are more accurate than low resolution high-precision forecasts of a similar computational cost. A spectral model based on the Surface Quasi-Geostrophic Equations is used to determine a power law describing how low precision can be safely reduced as a function of spatial scale; and experiments using four historical test-cases in an open-source version of the real-world Integrated Forecasting System demonstrate that a similar power law holds for the spectral part of this model. It is concluded that the scale-selective approach could be beneficially employed to optimally balance forecast cost and accuracy if utilised on real reduced precision hardware.
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Anderson, John W. "An analysis of a dust storm impacting Operation Iraqi Freedom, 25-27 March 2003." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FAnderson.pdf.
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Vasconi, Matteo. "Sensitivity of forecast skill to the parameterisation of moist convection in the COSMO model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14566/.
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The parameterisation of convection in limited-area models is an important source of uncertainty as regards the spatio-temporal forecast of precipitation.
The development and implementation of ensemble systems in which different convection schemes are used provides an opportunity to upgrade state-of-the-art probabilistic systems at the convection-parameterised scale. As for the limited-area model COSMO, the sensitivity of the forecast skill to the use of different convection schemes is assessed by performing different sets of experiments.
For one case of heavy precipitation over Italy, the performance of COSMO model run with the Bechtold scheme or with the Tiedtke scheme is investigated in both deterministic and ensemble modes with particular attention to the types of forecast errors (e.g. location, timing, intensity) provided by the different convection schemes in terms of total precipitation.
In addition to this, a 10-member ensemble has been run for approximately 2 months with the Bechtold scheme, using the same initial and boundary conditions as members 1-10 of the operational COSMO-LEPS ensemble system (which has 20 members, all run with the Tiedtke scheme). The performance of these members is assessed and compared to that of the system made of members 1-10 of COSMO-LEPS; in particular the spread/skill relation of the two 10-member ensembles in terms of total precipitation is evaluated. Finally, the performance of an experimental 20-member ensemble system (which has 10 members run with the Bechtold plus 10 members run with the Tiedtke scheme) is compared to that of operational COSMO-LEPS over the 2-month period. The new system turned out to have higher skill in terms of precipitation forecast with respect to COSMO-LEPS over the period. In this approach the use of the Bechtold scheme is proposed as a perturbation for the COSMO-LEPS ensemble, relatively to how uncertainties in the model representation of the cumulus convection can be described and quantified.
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Landry, Jennifer Jacobs. "Coastal Ocean Variability off the Coast of Taiwan in Response to Typhoon Morakot: River Forcing, Atmospheric Forcing, and Cold Dome Dynamics." Thesis, Massachusetts Institute of Technology (MIT), 2014. http://hdl.handle.net/10945/43427.
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CIVINSMultidisciplinary Simulation, Estimation, and Assimilation Systems, Reports in Ocean Science and Engineering, MSEAS-20
The ocean is a complex, constantly changing, highly dynamical system. Prediction capabilities are constantly being improved in order to better understand and forecast ocean properties for applications in science, industry, and maritime interests. Our overarching goal is to better predict the ocean environment in regions of complex topography with a continental shelf, shelfbreak, canyons and steep slopes using the MIT Multidisciplinary Simulation, Estimation and Assimilation Systems (MSEAS) primitive-equation ocean model. We did this by focusing on the complex region surrounding Taiwan, and the period of time immediately following the passage of Typhoon Morakot. This area and period were studied extensively as part of the intense observation period during August - September 2009 of the joint U.S. - Taiwan program Quantifying, Predicting, and Exploiting Uncertainty Department Research Initiative (QPE DRI). Typhoon Morakot brought an unprecedented amount of rainfall within a very short time period and in this research, we model and study the effects of this rainfall on Taiwan’s coastal oceans as a result of river discharge. We do this through the use of a river discharge model and a bulk river-ocean mixing model. We complete a sensitivity study of the primitive-equation ocean model simulations to the different parameters of these models. By varying the shape, size, and depth of the bulk mixing model footprint, and examining the resulting impacts on ocean salinity forecasts, we are able to determine an optimal combination of salinity relaxation factors for highest accuracy.
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Bender, Fabiani Denise. "Verificação da previsão do tempo em São Paulo com o modelo operacional WRF." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-19122012-120128/.
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Este estudo tem como objetivo a verificação das previsões diárias, das temperaturas máxima e mínima e precipitação acumulada, realizadas pelo modelo operacional de previsão numérica do tempo WRF (Weather Research Forecasting) para o estado de São Paulo. As condições iniciais e de fronteira fornecidas pela análise e previsão das 00UTC do modelo Global Forecast System (GFS), são usados no processamento do WRF, para previsões de 72 horas, em duas grades aninhadas (espaçamentos horizontais de grade de 50 km, D1, e 16,6 km, D2). O período avaliado foi de abril de 2010 a março de 2011. As comparações diárias das temperaturas máxima e mínima foram realizadas entre os valores preditos e observados nas estações de superfície de Registro, São Paulo, Paranapanema, Campinas, Presidente Prudente e Votuporanga (dados da CIIAGRO); através do erro médio (EM) e raiz do erro médio quadrático (REQM), para os prognósticos das 36, 60 e 72 horas. A precipitação acumulada diária é avaliada com relação ao produto MERGE, pela aplicação da ferramenta MODE, na previsão das 36 horas, para um limiar de 0,3 mm, no domínio espacial abrangendo o Estado de São Paulo e vizinhanças. Primeiramente, fez-se uma análise, comparando os pares de grade dos campos previsto e observado, utilizando os índices estatísticos de verificação tradicional de probabilidade de acerto (PA); índice crítico de sucesso (ICS); viés (VIÉS); probabilidade de detecção (PD) e razão de falso alarme (RFA). Posteriormente, foram analisados os campos de precipitação com relação à razão de área (RA); distância dos centroides (DC); razões de percentil 50 (RP50) e 90 (RP90). Os resultados evidenciaram que as saídas numéricas do modelo WRF com D2 tiveram desempenho melhor comparado à grade de menor resolução (maior espaçamento de grade horizontal, D1), tanto no prognóstico diário das temperaturas (máxima e mínima) quanto da precipitação acumulada. A temperatura apresentou um padrão de amortecimento, com temperaturas diárias máxima subestimada e mínima superestimada. Com relação à precipitação, as saídas numéricas do modelo GFS e WRF com D2 mostraram desempenho semelhante, com o D2 apresentando índices ligeiramente melhores, enquanto que as saídas numéricas do modelo WRF com D1 exibiram pior desempenho. Verificou-se um padrão de superestimativa, tanto em termos de abrangência espacial quanto em intensidade, para o modelo GFS e WRF em ambos os domínios simulados, ao longo de todo o período analisado. O percentil 50 é, geralmente, maior que o observado; entretanto, o percentil 90 é mais próximo ao observado. Os resultados também indicam que o viés dos modelos varia ao longo do ano analisado. Os melhores índices tanto com relação à precipitação quanto à temperatura foram obtidos para a estação de verão, com o modelo WRF com D2 apresentando melhores prognósticos. Entretanto, os modelos apresentam os maiores erros no inverno e no outono. Estes erros foram decorrentes de subestimativas das temperaturas máximas e superestimativas de área e intensidade de precipitação.Forecasts of daily maximum and minimum temperatures and rainfall performed by the operational numerical weather prediction WRF (Weather Research Forecasting) model in the São Paulo are evaluated. Initial and boundary conditions provided by the 00UTC Global Forecast System (GFS) Model and WRF run for 72 hours, with two nested grids (with horizontal grid spacing of 50 km, D1, and 16.6 km, D2). The study was made for April 2010 to March 2011 period. Daily maximum and minimum temperatures comparisons were made, between predicted and observed data of the surface weather stations of Registro, São Paulo, Paranapanema, Campinas, Presidente Prudente and Votuporanga (CIIAGRO Data), through the mean error (ME) and root mean square error(RMSE), for the 36, 60 and 72 hours forecasts. The daily accumulated rainfall is evaluated using MODE with respect to the MERGE product, for the 36 hours forecast, with threshold of 0.3 mm over the spatial domain covering the State of São Paulo and neighborhoods. First, an analysis was made comparing grid pairs of predicted and observed fields, through the traditional statistical verification indexes: accuracy (PA), critical success index (ICS), bias (VIES), probability of detection (PD) and false alarm ratio (RFA). Subsequently, we analyzed the precipitation field with respect to area ratio (AR), distance from the centroids (DC), ratio of the 50th percentile (RP50) and ratio of the 90th percentile (RP90). The WRF, with D2 nested grid, had better performance compared to the grid of lower space resolution (higher horizontal grid spacing, D1) for both, daily temperatures (maximum and minimum) and the accumulated rainfall forecasts. The temperature forecast presented a damped pattern, with underestimated maximum and overestimated minimum values. Rainfall was overall overestimated spatially and in intensity for the three models throughout the analized period. The forecasted 50th percentile is generally higher than that observed, however, the 90th percentile is closer to observations. The results also indicate that the bias of the models varies annually. The best performances for both rainfall and temperature were obtained for the summer season, with the D2 showing slightly better results. However, the models had the biggest errors during the winter and autumn seasons. These errors were due to underestimation of maximum temperatures and overestimation in area and intensity of precipitation.
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Bossavy, Arthur. "Caractérisation et prédiction probabiliste des variations brusques et importantes de la production éolienne." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00803234.
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L'énergie éolienne est aujourd'hui la source d'énergie renouvelable en plus forte expansion. Le caractère variable et partiellement contrôlable de sa production complexifie la gestion du système électrique. L'utilisation dans divers processus de décision, de prédictions du niveau de production à des horizons de 2-3 jours, permet une meilleure intégration de cette ressource. Certaines situations donnent néanmoins lieu à des performances de prédiction insatisfaisantes. Des erreurs dans la prédiction de l'instant d'apparition de variations brusques et importantes de la production, peuvent être responsables d'importants déséquilibres énergétiques, et avoir un impact négatif sur la gestion du système électrique. L'objectif de cette thèse est de proposer des approches permettant d'une part de caractériser ces variations, et d'autre part de prédire et d'estimer l'incertitude dans l'instant de leur apparition. Dans un premier temps, nous étudions différentes formes de caractérisation de ces variations. Nous proposons un modèle de rupture permettant de représenter le caractère aléatoire dans la proximité des ruptures d'un signal, tout en tenant compte des aspects borné et non-stationnaire du processus de production. A partir de simulations issues de ce modèle, nous réalisons une étude paramétrique destinée à évaluer et comparer les performances de différents filtres et approches multi-échelles de détection. Dans un deuxième temps, nous proposons une approche de prédiction probabiliste de l'instant d'apparition d'une rupture, reposant sur l'utilisation de prévisions météorologiques ensemblistes. Leur conversion en puissance fournit différents scénarii de la production, à partir desquels sont agrégées les prédictions de l'instant d'apparition d'une rupture. L'incertitude associée est représentée à l'aide d'intervalles de confiance temporels et de probabilités estimées conditionnellement. Nous évaluons la fiabilité et la finesse de ces estimations sur la base de mesures de production provenant de différentes fermes éoliennes.
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Sanz, Rodrigo Javier. "On antarctic wind engineering." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209953.
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Antarctic Wind Engineering deals with the effects of wind on the built environment. The assessment of wind induced forces, wind resource and wind driven snowdrifts are the main tasks for a wind engineer when participating on the design of an Antarctic building. While conventional Wind Engineering techniques are generally applicable to the Antarctic environment, there are some aspects that require further analysis due to the special characteristics of the Antarctic wind climate and its boundary layer meteorology. The first issue in remote places like Antarctica is the lack of site wind measurements and meteorological information in general. In order to complement this shortage of information various meteorological databases have been surveyed. Global Reanalyses, produced by the European Met Office ECMWF, and RACMO/ANT mesoscale model simulations, produced by the Institute for Marine and Atmospheric Research of Utrecht University (IMAU), have been validated versus independent observations from a network of 115 automatic weather stations. The resolution of these models, of some tens of kilometers, is sufficient to characterize the wind climate in areas of smooth topography like the interior plateaus or the coastal ice shelves. In contrast, in escarpment and coastal areas, where the terrain gets rugged and katabatic winds are further intensified in confluence zones, the models lack resolution and underestimate the wind velocity.
The Antarctic atmospheric boundary layer (ABL) is characterized by the presence of strong katabatic winds that are generated by the presence of surface temperature inversions in sloping terrain. This inversion is persistent in Antarctica due to an almost continuous cooling by longwave radiation, especially during the winter night. As a result, the ABL is stably stratified most of the time and, only when the wind speed is high it becomes near neutrally stratified. This thesis also aims at making a critical review of the hypothesis underlying wind engineering models when extreme boundary layer situations are faced. It will be shown that the classical approach of assuming a neutral log-law in the surface layer can hold for studies of wind loading under strong winds but can be of limited use when detailed assessments are pursued.
The Antarctic landscape, mostly composed of very long fetches of ice covered terrain, makes it an optimum natural laboratory for the development of homogeneous boundary layers, which are a basic need for the formulation of ABL theories. Flux-profile measurements, made at Halley Research Station in the Brunt Ice Shelf by the British Antarctic Survery (BAS), have been used to analyze boundary layer similarity in view of formulating a one-dimensional ABL model. A 1D model of the neutral and stable boundary layer with a transport model for blowing snow has been implemented and verified versus test cases of the literature. A validation of quasi-stationary homogeneous profiles at different levels of stability confirms that such 1D models can be used to classify wind profiles to be used as boundary conditions for detailed 3D computational wind engineering studies.
A summary of the wind engineering activities carried out during the design of the Antarctic Research Station is provided as contextual reference and point of departure of this thesis. An elevated building on top of sloping terrain and connected to an under-snow garage constitutes a challenging environment for building design. Building aerodynamics and snowdrift management were tested in the von Karman Institute L1B wind tunnel for different building geometries and ridge integrations. Not only for safety and cost reduction but also for the integration of renewable energies, important benefits in the design of a building can be achieved if wind engineering is considered since the conceptual phase of the integrated building design process.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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García, León Manuel. "Coastal risk forecast system : fostering proactive management at the Catalan coast." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/669662.
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The action of sea storms is one of the most complex littoral processes with deep management implications. Along the Catalan shoreline which is about 700 km long, 190 km are subject to erosion and/or flooding. Around one million people live in areas potentially affected. Sea Level Rise could exacerbate this problem in the near future. Reactive interventions have been the norm in coastal engineering and management. This dissertation proposes a pre-storm strategy that foster cost-effective eco-compatible measures, termed Quick Defence Measures (QDM). Pre-storm intervention requires to forecast the future post-storm state. Hence, the main objective of this thesis is to assess present coastal risk through a Coastal Early Warning System (CEWS), termed LIM-COPAS, that forecasts the more relevant episodic coastal hazards at the area.
LIM-COPAS consists of four modules: (i) meteorological model; (ii) wave generation/propagation code; (iii) coupled morpho-hydrodynamic model and (iv) risk module via non-stationary multivariate probabilistic models. The performance of this suite of models has been tested with (i) a set of hindcast events and (ii) synthetic storm conditions. The hindcasted events have been: December 2008 (D-08); October-2015 (O-15); November 2015 (N-15); January 2016 (J-16); February 2016 (F-16); December 2016 (D-16) and January 2017 (J-17).
In D-08, errors in nearshore spectral wave parameters have been about twice than those in the offshore area. The error was around 20% in hydrodynamics and 50% in morphodynamics. The post-storm response has been acceptably reproduced, with a Brier Skill Score near 0.4.
LIM-COPAS has shown good accuracy with high return period events (i.e. Tr,waves > 10 yrs, D-16 and J-17), but lower agreement was found for milder storms (i.e. O-15 and F-16).
The meteorological module provided wind fields that were systematically overestimated. The integrated Mean Bias (MB) was -1.52 ± 0.78 m/s. Tarragona (Coefficient of Efficiency, COE = 0.27 ± 0.13) and Begur (COE = 0.29 ± 0.17) had metrics above the average value (COE = 0.24 ± 0.14); but lower agreement was found at Mahón (COE = 0.13 ± 0.16) and Dragonera.
Wave metrics were more accurate than for the wind fields. The integrated Hs COE was 0.52±0.12 and Tm02 COE was 0.36±0.14. At the central coast, Hs has presented good metrics: low MB (-0.06 ± 0.08 m) and high COE (0.58 ± 0.11). The northern coast metrics were the most stable.
The newly developed risk module has been implemented at 79 beaches. Erosion has been estimated as a bounded cost, whereas flooding as a high upside cost. Dissipative beaches tend to exhibit higher costs than reflective beaches under high sea levels. Tr,waves < 10 yrs events joint with storm-surges can lead to significant damage costs. The estimated losses for the N-15 event (2510·10^3 euros) do not differ excessively from J-17 (3200·10^3 euros).
Two types of QDM have been numerically tested: (i) sand dunes and (ii) geotextile detached breakwaters. The benefits from maintaining the sand volumes outperform the flooding cost reduction. In general terms, the detached breakwater can be a suitable option for beaches in an intermediate morphodynamic state against low to moderate sea levels and high wave return periods. At dissipative beaches, dunes are the best option, but they require a minimum beach width (around 30 m) that ensures their lifetime.
QDM functionality can be enhanced with compatible long-term actions (nourishments, sand bypasses, submerged vegetation, etc.). A healthy beach state is paramount for the QDM effectiveness. A higher sustainable management under present and future climate can be reached with the joint combination of (i) CEWS as a short-term forecasting tool; (ii) QDM that mitigate storm impacts and (iii) long-term interventions that improves the beach health.La acción de los temporales de mar es uno de los procesos litorales más complejos, con profundas implicaciones en la gestión del litoral. A lo largo de la línea de costa catalana, 190 km están sometidos a erosión y/o inundación. Cerca de un millón de personas viven en áreas potencialmente afectadas. La tradición en ingeniería y gestión costera han sido intervenciones reactivas. Esta tesis propone una estrategia pre-tormenta que fomente una serie de medidas eco-compatibles, denominadas Medidas de Acción Rápida (MAR). Las intervenciones pre-tormenta requieren predecir el estado post-temporal de la costa. Por tanto, el principal objetivo de esta tesis es evaluar el riesgo costero episódico mediante un Sistema de Alarma Temprana Costero (CEWS), denominado LIM-COPAS, que predice las peligrosidades costeras más relevantes en dicha área. LIM-COPAS consiste de cuatro módulos: (i) modelo meteorológico; (ii) código de generación/propagación del oleaje; (iii) modelo acoplado morfo-hidrodinámico y (iv) un módulo de riesgo vía modelos probabilísticos multivariantes y no-estacionarios. El comportamiento de estos módulos ha sido analizado mediante (i) una serie de eventos pasados y (ii) temporales sintéticos. Los eventos pasados han sido: Diciembre 2008 (D-08); Octubre 2015 (O-15); Noviembre 2015 (N-15); Enero 2016 (J-16); Febrero 2016 (F-16); Diciembre 2016 (D-16) y Enero 2017 (J-17). En D-08, los errores en los parámetros espectrales de oleaje costero han sido casi el doble que en mar abierto. El error ha sido del 20% en la hidrodinámica y del 50% en la morfodinámica. La respuesta post-temporal ha sido reproducida aceptablemente, con Brier Skill Score cercanos a 0.4. LIM-COPAS ha demostrado buena precisión con tormentas de alto período de retorno (i.e. Tr,waves _ 10 yrs, D-16 y J-17), pero menor concordancia fue encontrada para las tormentas moderadas (i.e. O-15 y F-16). El módulo meteorológico estimó campos de viento que fueron sistemáticamente sobreestimados. El Sesgo Medio (MB) integrado fue de −1,52 ± 0,78 m/s. Tarragona (Coeficiente de Eficiencia, COE = 0,27±0,13) y Begur (COE = 0,29±0,17) tuvieron métricas por encima de la media (COE = 0,24±0,14); no obstante, peor ajuste se encontró en Mahón (COE = 0,13 ± 0,16) y Dragonera. Las métricas de oleaje fueron más precisas que las del viento. Hs COE integrada fue 0,52±0,12 y Tm02 COE fue 0,36±0,14. En la costa central, Hs presentó buenas métricas: bajo MB (−0,06 ± 0,08 m) y alto COE (0,58 ± 0,11). Las métricas en la costa norte fueron las más estables. El módulo de riesgo ha sido implementado en 79 playas. La erosión se ha estimado como un coste acotado, mientras que la inundación como un coste con alta cota superior. Las playas disipativas tienden a exhibir mayores costes que las playas reflejantes bajo altos niveles del mar. Episodios con Tr,waves _ 10yrs, concomitantes a mareas meteorológicas pueden conllevar costes significantes. Las pérdidas estimadas para N-15 (2510 · 103euros) no difieren en exceso de J-17 (3200 · 103 euros). Dos tipos de MAR han sido testeadas numéricamente: (i) dunas y (ii) diques exentos constituídos por geotextiles llenos de arena. Los beneficios de mantener estables los volúmenes de arena superan la reducción de los costes por inundación. En términos generales, los diques exentos pueden ser una opción adecuada para playas de estado morfodinámico intermedio frente a oleaje de alto período de retorno y niveles del mar bajos a moderados. En playas disipativas, las dunas son la mejor opción, pero requieren un ancho mínimo de playa (cerca de 30 m) que garantice su vida útil. La funcionalidad de las MAR puede mejorarse mediante acciones compatibles a largo-plazo (alimentaciones, bypass de arena, vegetación sumergida, etc.). Un estado de playa saludable es esencial para la efectividad de las MAR. Una gestión más sostenible bajo clima presente y futuro puede ser alcanzada mediante (i) CEWS como herramienta de predicción a corto plazo; (ii) MAR que mitiguen los impactos de los temporales y (iii) intervenciones a largo-plazo que mejoren la salud de la costa.
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Trapero, i. Bagué Laura. "Modelització de precipitacions intenses en zones d'orografia complexa: casos d'estudi al Pirineu Oriental." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285202.
Full textAbstract:
Els episodis de precipitació intensa en zones de muntanya sovint es veuen afavorits pels efectes orogràfics que actuen com a mecanismes que modifiquen la precipitació. Aquest treball vol contribuir a millorar el coneixement dels processos fonamentals que afecten la precipitació quan aquesta té lloc en una zona d'orografia complexa com és el cas de la zona oriental dels Pirineus, situada a la Mediterrània nord-occidental. En aquest treball de tesi, a partir de modelitzacions numèriques d'alta resolució realitzades amb els models WRF i MESO-NH de nou casos d'estudi diferents, s'investiguen les condicions sinòptiques i mesoescalars que afavoreixen el desenvolupament dels sistemes de precipitació als Pirineus Orientals. Entre d'altres, s'ha analitzat l'episodi del 7 novembre de 1982, que es troba entre els més intensos a Europa durant el període 1950-2005, en concret a Andorra, aquest ha estat l'episodi de risc que ha causat més morts al país. Els resultats obtinguts de les simulacions amb passos de malla horitzontal a 2,5 i 2 km reprodueixen estructures de precipitació amb una distribució i intensitat en concordança amb les observacions. Tot i això, també s'ha examinat la incertesa associada a la sensibilitat que mostra la modelització a variacions en les condicions inicials i a la microfísica.
L'anàlisi mesoescalar s'ha dut a terme tant per a episodis caracteritzats per fluxos estables com condicionalment inestables. A la primera part del treball s'ha examinat l'efecte de l'orografia en la localització i intensitat dels sistemes de precipitació. L'anàlisi s'ha fet a partir de l'aplicació dels resultats extrets tant de simulacions numèriques idealitzades com de casos d'estudi en altres regions muntanyoses. Pels episodis condicionalment inestables amb condicions atmosfèriques que evolucionen molt ràpidament com és el cas de les ciclogènesis mediterrànies, l'anàlisi de dos dels paràmetres adimensionals (activació de la convecció i el nombre de Froude humit) reflecteix la complexitat d'aplicar aquests resultats teòrics. En canvi, pels episodis hivernals de nord sota condicions estables, el camp de precipitació mostra una dependència segons el nombre de Froude representatiu del flux incident. Els comportaments identificats s'han resumit en forma de model conceptual.
A la segona part, l'anàlisi mesoescalar centrat en la descripció de la interacció entre el flux i la complexa orografia dels Pirineus ha permès identificar diferents factors tant dinàmics com microfísics que contribueixen a reforçar la precipitació orogràfica. Les retrotrajectòries basades en els traçadors eulerians passius, indiquen que l'ascens orogràfic directe és el principal mecanisme que desencadena la formació dels sistemes de precipitació als Pirineus. Mentre que, sota condicions atmosfèriques estables, les simulacions detecten la formació d'un màxim de vent al vessant nord paral•lel a la serralada a causa del marcat efecte de bloqueig exercit pels Pirineus. En canvi, per certes situacions mesoescalars, a l'extrem est de la serralada es forma una zona de confluència molt marcada que al mateix temps afavoreix la formació d'un corrent de densitat molt ben organitzat. La influència dels processos microfísics implicats en el reforç de la precipitació s'ha estudiat per mitjà de l'anàlisi de la distribució vertical dels hidrometeors. Les estructures verticals descrites són coherents amb els models conceptuals proposats a partir de les campanyes observacionals realitzades en altres regions muntanyoses com poden ser els Alps. Un dels mecanismes suggerits com a dominants en el procés d'intensificació de la precipitació està relacionat amb la formació del calabruix.
S'ha realitzat l'anàlisi lagrangiana del flux d'alimentació dels sistemes de precipitació en episodis condicionalment inestables. Els resultats de les simulacions indiquen una important dependència de la intensitat de la precipitació als Pirineus amb dos factors: el component del vent perpendicular a la serralada i el transport d'humitat cap als Pirineus a la baixa troposfera. S'han suggerit diferents rangs de valors per tal de discriminar els episodis segons la intensitat de la precipitació orogràfica. En conjunt, i d'acord amb els resultats obtinguts a partir de simulacions idealitzades, es pot dir que com més fort sigui el camp de vent incidint perpendicular a la serralada i més elevada l'advecció d'humitat, més intensa serà la precipitació als Pirineus. Per l'episodi hivernal estudiat més intens, la detecció d'un corrent atmosfèric en forma de banda estreta i allargada amb un transport molt elevat d'humitat provinent de latituds equatorials (550 kg/m•s; atmospheric river en anglès) va contribuir clarament en la forta nevada. Una situació similar però molt més perillosa, va succeir el 1982 quan gràcies a la presència d'un màxim de vent de 30 m/s a 1500 m, la part càlida i molt humida situada davant una pertorbació Atlàntica va incidir directament sobre els Pirineus Orientals i va persistir durant més de 10 h. Per aquest darrer episodi, també s'ha comprovat la contribució limitada del Mediterrani com a font local d'humitat (2-3 g/kg), en contraposició a l'elevada quantitat d'humitat (7-9 g/kg) provinent de les fonts remotes (latituds subtropicals Atlàntiques i nord d'Àfrica).Heavy precipitation events over complex terrain are often favoured by enhancement mechanisms of precipitation. The windward slopes of the Eastern Pyrenees, as other mountainous Mediterranean regions, are regularly affected by heavy precipitation events (HPE). This present work benefits from high resolution numerical simulations of several case studies to investigate the synoptic and mesoscale environment favourable to precipitating systems development over the Eastern Pyrenees. The mesoscale models WRF and MESO-NH run at horizontal grid-lengths of 2.5-2 km have reproduced realistic precipitation structures over the Pyrenees but the uncertainty associated to sensitivities to initial conditions and microphysics has also been highlighted. The analysis has been done for both stable and conditionally unstable conditions. The former part of the analysis has explored the application of the results from purely idealized simulations or previous studies in other mountainous regions to the case study simulations. For conditionally unstable events with dynamic evolving conditions (Mediterranean cyclogenesis), the analysis of a triggering term and the moist Froude number reflects the complexity of applying theoretical results. On the other hand, for winter northerly stable flows the precipitation field reveals a dependency on the upstream Froude number. These patterns are synthesised in a conceptual model. Backward trajectories based on Eulerian on-line passive tracers indicate that the direct orographic lifting is the main forcing mechanism which triggers precipitating systems over the Pyrenees. For stable conditions, the simulations capture the formation of an along barrier flow in the north slope due to the blocking effect exerted by the Pyrenees. Under specific mesoscale configurations, a distinct confluence zone is also formed in the easternmost part of the massif, which in turn favours the generation of a well developed density current. The understanding of the microphysical processes involved in precipitation enhancement has been examined by means of the hydrometeor vertical distribution. The dominant mechanisms for intense precipitation are associated with graupel. From the lagrangian analysis of the feeding flow in the conditionally unstable episodes, the simulations indicate a marked dependence of the precipitation intensity over the Pyrenees on two factors: the cross-barrier wind intensity and the moisture advection towards the Pyrenees in the lower atmosphere. Different ranges have been suggested to discriminate the orographic precipitation intensity over the Pyrenees. In general, the stronger the cross-barrier component wind and the water vapour flux the more intense the orographic precipitation will be. During the most intense winter event, the detection of a narrow corridor of strong water vapour transport (atmospheric river; 550 kg/m•s) contributed to the generation of persistent precipitation. A similar situation occurred during the 1982 HPE when the Atlantic moist and warm conveyor belt combined with a LLJ (30 m/s) impinged over the Eastern Pyrenees more than 10 h. For this last episode, it has been also proved the limited role of the Mediterranean as local moisture source (2-3 g/kg) as the moisture coming from remote source regions (subtropical Atlantic and Africa) is larger (7-9 g/kg).
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Kurzrock, Frederik. "Assimilation de données satellitaires géostationnaires dans des modèles atmosphériques à aire limitée pour la prévision du rayonnement solaire en région tropicale." Thesis, La Réunion, 2019. https://elgebar.univ-reunion.fr/login?url=http://thesesenligne.univ.run/19_13_FKurzrock.pdf.
Full textAbstract:
La variabilité de l’énergie solaire impose de limiter sa fraction d’injection instantanée dans le réseau électrique. Une amélioration des prévisions de l’ensoleillement conduirait à élever la limite de ce seuil, spécialement dans les zones non-interconnectées comme La Réunion. Une plus haute précision de prévision est particulièrement difficile à atteindre dans le cas des îles tropicales à cause de la convection prononcée et des circulations thermiques complexes au niveau local. Les modèles de prévision numérique du temps à aire limitée permettent de prévoir les processus liés aux nuages et l'éclairement solaire à de hautes résolutions spatio-temporelles, de l’ordre de quelques kilomètres et minutes. Néanmoins, ces modèles parviennent rarement à prévoir précisément l'évolution de la couche nuageuse et ont donc tendance à surestimer l'éclairement solaire. L’affinement des conditions initiales nuageuses des modèles régionaux par l’assimilation d’observations de satellites météorologiques géostationnaires est un moyen efficace pour améliorer les prévisions à court terme. Toutefois, une grande variété d'approches pour l'assimilation des données satellitaires existe et, jusqu'à présent, la recherche s’est concentrée sur les moyennes latitudes. Cette thèse aborde l'assimilation d'observations de satellites géostationnaires avec des modèles à aire limitée dans le sud-ouest de l'Océan Indien. Dans un premier temps, l'état de l'art des approches existantes pour l'assimilation de luminances observées et de propriétés physiques des nuageuse avec les modèles régionaux est dressé. Puis, l'une des approches les plus prometteuses est identifiée et appliquée au sud-ouest de l'Océan Indien. Dans les expériences effectuées, la teneur en eau des nuages est obtenue à partir des produits de propriétés nuageuses SatCORPS de la NASA. Ces observations sont assimilées avec un filtre de Kalman d’ensemble et le modèle Weather Research and Forecasting. Un ensemble de 41 membres et un espacement horizontal des points de grille de 12 km est appliqué avec un intervalle de cyclage de 6 heures pour l'assimilation. Le Data Assimilation Research Testbed et son opérateur d'observations de teneur en eau des nuages sont utilisés pour l'assimilation d'observations dans les phases solide, surfondue, et liquide. L'impact de cette approche d'assimilation sur des prévisions de l'éclairement horizontal global est évalué pour l'été austral 2017/2018 en utilisant des observations de pyranomètres sur l'île de La Réunion. Un effet positif de la méthode appliquée sur les prévisions de l'éclairement est constaté surtout pour les 14 premières heures de prévision. Différents aspects de l'amélioration des prévisions, grâce à l'assimilation de données, sont analysés par le biais d’expériences témoins sans assimilation, d’expériences avec un domaine de grille imbriquée avec un espacement horizontal des points de grille de 4 km et d’une comparaison avec des modèles opérationnels. Les observations quadrillées utilisées étant disponibles à l'échelle mondiale, la méthode offre une approche applicable et évaluable pour d'autres régions du mondeThe variability of solar irradiance necessitates to limit the instantaneous feed-in of solar power to electricity grids. An improvement of solar irradiance forecasts would allow to increase the defined threshold limits, especially in non-interconnected zones such as Reunion Island. Achieving higher forecast accuracy is particularly challenging in the case of tropical islands due to pronounced convection and local thermal circulations. Limited-area numerical weather prediction (NWP) models allow to forecast cloud processes and solar irradiance at high spatio-temporal resolutions of a few kilometres and minutes. Nevertheless, they often fail to accurately predict cloudiness evolution and thus tend to overestimate solar irradiance. Refining the initial conditions of regional models in terms of clouds is an efficient means for improving short-term cloud cover and irradiance forecasts. The assimilation of geostationary meteorological satellite observations can achieve this improvement. Nevertheless, a variety of satellite data assimilation (DA) approaches exist and research has focused on mid-latitudes so far. This thesis deals with the assimilation of geostationary satellite observations with limited-area models in the southwestern Indian Ocean. In a first step, the state of the art in terms of existing approaches for radiance and cloud property retrieval assimilation with regional-scale models is reviewed. In consequence, one of the most promising approaches is identified and applied to the southwestern Indian Ocean. In the performed experiments, multi-phase cloud water path retrievals from NASA Langley's SatCORPS cloud products are assimilated with an ensemble Kalman filter using the Weather Research and Forecasting model. A 41-member ensemble at 12 km grid spacing is applied with a DA cycling interval of 6 hours. The Data Assimilation Research Testbed and its forward operator for cloud water path are used to assimilate gridded cloud water retrievals in the ice, supercooled liquid, and liquid phase. The impact of this assimilation approach on forecasts of global horizontal irradiance (GHI) is evaluated for austral summer 2017/2018 using pyranometer observations on Reunion Island. A distinct positive impact of the applied method on the first 14 hours of GHI forecasts is found. Different aspects of the forecast improvement due to DA are analysed by means of control experiments without DA, experiments with a nested domain at 4 km grid spacing, and a comparison with operational NWP models. As the utilised gridded cloud products are available globally, the method offers a portable and globally applicable approach that may also be evaluated for other regions of the Earth
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Roeger, Claudia. "Verification of numerical weather prediction and avalanche forecasting." Thesis, 2001. http://hdl.handle.net/2429/11590.
Full textAbstract:
This thesis is an attempt to help weather and avalanche forecasters in their decisionmaking
process based on meteorological predictions by (1) quantifying some of the many
uncertainties of meteorological forecasts and (2) combining numerical weather and
avalanche prediction.
In particular, output from two numerical weather prediction models was verified with
surface data from two study sites: the ski area Whistler/Blackcomb in the Coast
Mountains and the highway operation Kootenay Pass in the southern Selkirk Mountains.
They represent two different mountain climates in British Columbia. The two highresolution,
real-time, numerical weather forecast models that were running at U B C make
daily forecasts on multiple nested grids out to 48 hours into the future. Domains with
grid-point spacings of 2 km, 10 km, and 30 km were used for Kootenay Pass. At
Whistler/Blackcomb, the grid-point spacings were 3.3 km and 10 km.
Both weather models perform well. Temperature and wind predictions are very accurate
with the post-processing Kalman-predictor correction method. Precipitation amount is
under-forecast, which should be considered when used in avalanche prediction. The
model with the 30 km grid spacing has comparable results to the higher-resolution model.
The 2km-grid of this model performs slightly better than the corresponding lOkm-grid at
the Kootenay Pass stations. 24-hour forecasts were generally more accurate than 48-hour
forecasts.
The forecast output for Kootenay Pass was used as input for a local avalanche forecasting
model. This 24-hour avalanche forecast was verified against observed avalanche
occurrence and against the 12-hour avalanche forecast with current weather observations.
The combination of numerical weather prediction and numerical avalanche forecasting
looks very promising. The avalanche model output for the test run with numerically
predicted weather data is very similar to the run with observed weather data. This
indicates that avalanches may be predicted statistically out to 24 hours into the future
with high-resolution numerical weather prediction as input. However, the weather and
avalanche forecast errors should be taken into account during operational use.
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Harper, Kristine C. "Boundaries of research : civilian leadership, military funding, and the international network surrounding the development of numerical weather prediction in the United States." Thesis, 2003. http://hdl.handle.net/1957/30321.
Full textAbstract:
American meteorology was synonymous with subjective weather forecasting in the
early twentieth century. Controlled by the Weather Bureau and with no academic
programs of its own, the few hundred extant meteorologists had no standing in the
scientific community. Until the American Meteorological Society was founded in
1919, meteorologists had no professional society. The post-World War I rise of
aeronautics spurred demands for increased meteorological education and training.
The Navy arranged the first graduate program in meteorology in 1928 at MIT. It
was followed by four additional programs in the interwar years. When the U.S.
military found itself short of meteorological support for World War II, a massive
training program created thousands of new mathematics- and physics-savvy
meteorologists. Those remaining in the field after the war had three goals: to create
a mathematics-based theory for meteorology, to create a method for objectively
forecasting the weather, and to professionalize the field. Contemporaneously,
mathematician John von Neumann was preparing to create a new electronic digital
computer which could solve, via numerical analysis, the equations that defined the
atmosphere. Weather Bureau Chief Francis W. Reichelderfer encouraged von
Neumann, with Office of Naval Research funding, to attack the weather forecasting
problem. Assisting with the proposal was eminent Swedish-born meteorologist
Carl-Gustav Rossby. Although Rossby returned to Stockholm to establish his own
research school, he was the de facto head of the Meteorology Project providing
personnel, ideas, and a publication venue. On-site leader Jule Charney provided the
equations and theoretical underpinnings. Scandinavian meteorologists supplied by
Rossby provided atmospheric reality. Six years after the Project began,
meteorologists were ready to move their models from a research to an operational
venue. Attempts by Air Force meteorologist Philip D. Thompson to co-opt
numerical weather prediction (NWP) prompted the academics, Navy, and Weather
Bureau members involved to join forces and guarantee that operational NWP
would remain a joint activity not under the control of any weather service. This is
the story of the professionalization of a scientific community, of significant
differences in national styles in meteorology, and of the fascination (especially by
non-meteorologists) in exploiting NWP for the control of weather.Graduation date: 2003
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Jordan, Mark Rickman Krishnamurti T. N. "Using the superensemble method to improve Eastern Pacific tropical cyclone forecasting." Diss., 2005. http://etd.lib.fsu.edu/theses/available/etd-09212005-152853.
Full textAbstract:
Thesis (M.S.)--Florida State University, 2005.Advisor: T. N. Krishnamurti, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Jan. 26, 2006). Document formatted into pages; contains xi, 64 pages. Includes bibliographical references.
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Cartwright, Tina Johnson Krishnamurti T. N. "Warm season mesoscale superensemble precipitation forecasts." 2004. http://etd.lib.fsu.edu/theses/available/etd-10252004-132554.
Full textAbstract:
Thesis (Ph. D.)--Florida State University, 2004.Advisor: Dr. T.N. Krishnamurti, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Jan. 14, 2005). Includes bibliographical references.
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Smith, Travis Allen Cunningham Philip. "Analysis and evolution of balance in unstable barotropic jets." 2004. http://etd.lib.fsu.edu/theses/available/etd-07022004-115226.
Full textAbstract:
Thesis (M.S.)--Florida State University, 2004.Advisor: Dr. Philip Cunningham, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 22, 2004). Includes bibliographical references.
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Yen-Ming, Chiang. "Artificial Neural Networks in Hydrometeorology-Flood Forecasting from Radar and Numerical Weather Prediction Information." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1801200717585100.
Full text
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Chiang, Yen-Ming, and 江衍銘. "Artificial Neural Networks in Hydrometeorology-Flood Forecasting from Radar and Numerical Weather Prediction Information." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/43407252787836895747.
Full textAbstract:
博士國立臺灣大學
生物環境系統工程學研究所
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The major purpose of this dissertation is to effectively construct artificial neural networks-based multi-step-ahead flood forecasting using radar and numerical weather prediction information. To achieve this goal, three investigations by using neural networks for rainfall estimation and/or rainfall-runoff process simulation have been performed to explore their accuracy and applicability. The first topic investigates the model forecasts through static and dynamic neural networks by using four sets of training data which consist of different sample sizes and contents. Performance of these two types of networks suggest that the dynamic neural network generally could produce better and more stable forecasts than the static neural network, and the static model could produce satisfactory results only when sufficient and adequate training data are provided. The second topic focuses on the evaluation of effectiveness and stability of three neural networks-based multi-step-ahead forecasts in terms of model structures. The results indicate that a neural network with a serial-propagated structure can help in improving the accuracy of forecasts. This concept not only provides a possibility of finding better solution for multi-step-ahead forecasts but enhances the predictive reliability. Results from above two studies are further utilized in the third topic which is to construct a precise and feasible multi-step-ahead flood forecasting. For better multi-step-ahead flood forecasting, there is a necessity to conduct the predicted meteorological information. Therefore, an improved quantitative precipitation forecasting is obtained from a merging procedure that combines radar-derived predictions and precipitation forecasts extracted from a numerical weather prediction model. The comparison of multi-step-ahead flood forecasting derived from the serial- propagated structure and the merged precipitation prediction is made by estimating the timing and the percent error of a predicted peak flow relate to observed peak flow and the corresponding improvement. Based on the comprehensive comparison, the merging procedure successfully demonstrates the capability of efficiently combining the information from both rainfall sources and improves the accuracy of 1-6 h precipitation predictions. For multi-step-ahead flood forecasting, an important finding is the hydrologic responses seem not sensitive to the precipitation predictions in short lead times (in our case 1 to 3 hours) but dominate by previous runoff information, whereas the model forecasts are highly dependent on predicted precipitation information for lead time greater than 3 hours. Overall, the results strongly demonstrate that accurate and stable multi-step-ahead flood forecasting can be obtained from a serial-propagated structure and enhanced by the proposed precipitation predictions.
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Lin, Lin Jin Feifei. "A numerical analysis of the first-order closure for synoptic eddy and low-frequency flow (SELF)-feedback." Diss., 2005. http://etd.lib.fsu.edu/theses/available/etd-07112005-160540/.
Full textAbstract:
Thesis (M. S.)--Florida State University, 2005.Advisor: Dr. Feifei Jin, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains vii, 42 pages. Includes bibliographical references.
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Ventham, Justin D. "Large scale environmental wind patterns and the intensification rates of western north Pacific tropical storms." 2005. http://proquest.umi.com/pqdweb?index=0&did=1042535681&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1263238934&clientId=23440.
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Malakar, Preeti. "Integrated Parallel Simulations and Visualization for Large-Scale Weather Applications." Thesis, 2013. http://etd.iisc.ernet.in/2005/3907.
Full textAbstract:
The emergence of the exascale era necessitates development of new techniques to efficiently perform high-performance scientific simulations, online data analysis and on-the-fly visualization. Critical applications like cyclone tracking and earthquake modeling require high-fidelity and high- performance simulations involving large-scale computations and generate huge amounts of data. Faster simulations and simultaneous online data analysis and visualization enable scientists provide real-time guidance to policy makers.
In this thesis, we present a set of techniques for efficient high-fidelity simulations, online data analysis and visualization in environments with varying resource configurations. First, we present a strategy for improving throughput of weather simulations with multiple regions of interest. We propose parallel execution of these nested simulations based on partitioning the 2D process grid into disjoint rectangular regions associated with each subdomain. The process grid partitioning is obtained from a Huffman tree which is constructed from the relative execution times of the subdomains. We propose a novel combination of performance prediction, processor allocation methods and topology-aware mapping of the regions on torus interconnects. We observe up to 33% gain over the default strategy in weather models.
Second, we propose a processor reallocation heuristic that minimizes data redistribution cost while reallocating processors in the case of dynamic regions of interest. This algorithm is based on hierarchical diffusion approach that uses a novel tree reorganization strategy. We have also developed a parallel data analysis algorithm to detect regions of interest within a domain. This helps improve performance of detailed simulations of multiple weather phenomena like depressions and clouds, thereby in- creasing the lead time to severe weather phenomena like tornadoes and storm surges. Our method is able to reduce the redistribution time by 25% over a simple partition from scratch method.
We also show that it is important to consider resource constraints like I/O bandwidth, disk space and network bandwidth for continuous simulation and smooth visualization. High simulation rates on modern-day processors combined with high I/O bandwidth can lead to rapid accumulation of data at the simulation site and eventual stalling of simulations. We show that formulating the problem as an optimization problem can deter- mine optimal execution parameters for enabling smooth simulation and visualization. This approach proves beneficial for resource-constrained environments, whereas a naive greedy strategy leads to stalling and disk overflow. Our optimization method provides about 30% higher simulation rate and consumes about 25-50% lesser storage space than a naive greedy approach.
We have then developed an integrated adaptive steering framework, InSt, that analyzes the combined e ect of user-driven steering with automatic tuning of application parameters based on resource constraints and the criticality needs of the application to determine the final parameters for the simulations. It is important to allow the climate scientists to steer the ongoing simulation, specially in the case of critical applications. InSt takes into account both the steering inputs of the scientists and the criticality needs of the application.
Finally, we have developed algorithms to minimize the lag between the time when the simulation produces an output frame and the time when the frame is visualized. It is important to reduce the lag so that the scientists can get on-the- y view of the simulation, and concurrently visualize important events in the simulation. We present most-recent, auto-clustering and adaptive algorithms for reducing lag. The lag-reduction algorithms adapt to the available resource parameters and the number of pending frames to be sent to the visualization site by transferring a representative subset of frames. Our adaptive algorithm reduces lag by 72% and provides 37% larger representativeness than the most-recent for slow networks.
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(10285328), Connor Paul Belak. "Verification of simulated DSDs and sensitivity to CCN concentration in EnKF analysis and ensemble forecasts of the 30 April 2017 tornadic QLCS during VORTEX-SE." Thesis, 2021.
Find full textAbstract:
Storms in the SE-US often evolve in different environments than those in the central Plains. Many poorly understood aspects of these differing environments may impact the tornadic potential of SE-US storms. Among these differences are potential variations in the CCN concentration owing to differences in land cover, combustion, industrial and urban activity, and proximity to maritime environments. The relative influence of warm and cold rain processes is sensitive to CCN concentration, with higher CCN concentrations producing smaller cloud droplets and more efficient cold rain processes. Cold rain processes result in DSDs with relatively larger drops from melting ice compared to warm rain processes. Differences in DSDs impact cold pool and downdraft size and strength, that influence tornado potential. This study investigates the impact of CCN concentration on DSDs in the SE-US by comparing DSDs from ARPS-EnKF model analyses and forecasts to observed DSDs from portable disdrometer-equipped probes collected by a collaboration between Purdue University, the University of Oklahoma (OU), the National Severe Storms Laboratory (NSSL), and the University of Massachusetts in a tornadic QLCS on 30 April 2017 during VORTEX-SE.
The ARPS-EnKF configuration, which consists of 40 ensemble members, is used with the NSSL triple-moment microphysics scheme. Surface and radar observations are both assimilated. Data assimilation experiments with CCN concentrations ranging from 100 cm-3 (maritime) to 2,000 cm-3 (continental) are conducted to characterize the variability of DSDs and the model output DSDs are verified against the disdrometer observations. The sensitivity of the DSD variability to CCN concentrations is evaluated. Results indicate continental CCN concentrations (close to CCN 1,000 cm3) produce DSDs that align closest to the observed DSDs. Other thermodynamic variables also accord better to observations in intermediate CCN concentration environments.