To see the other types of publications on this topic, follow the link: 3D general circulation model.
Dissertations / Theses on the topic '3D general circulation model'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic '3D general circulation model.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Böttger, Henning M. "Modelling the water cycle on Mars." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289340.
Full text
2
Sparrman, Viktor. "Estimates of Fractional Habitability for Proxima Centauri b using a 3D GCM." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-415703.
Full textAbstract:
Exoplanet discovery has grown more quickly in recent years. However, the nature of their discovery leaves many unanswered in questions regarding exoplanetary habitability. Proxima Centauri b, an exoplanet which orbits the Sun's closest stellar neighbour, Proxima Centauri, was recently discovered with a subzero equilibrium temperature. Although not considered habitable based on the classical definition of the liquid water range, there may be fractions of Proxima Centauri b which are habitable. A prior study simulated the climate conditions of Proxima Centauri b until equilibrium was reached, using a variety of initial conditions. In this project, various metrics for calculating the fractional habitability of Proxima Centauri b are presented and applied to the results of the prior study's simulations. Colormaps are used to show the ice and temperature distributions that produce the calculated values of fractional habitability. The fractional habitabilities calculated show that while the value is both case and metric dependent, for the vast majority of all cases and metrics the value is nonzero implying that Proxima Centauri b is likely to have habitable regions.Upptäckandet av exoplaneter har ökat i takt över de senaste åren. Samtidigt, på grund av sättet som de upptäcks finns många obesvarade frågor angående planeternas beboelighet. Proxima Centauri b är en exoplanet som kretsar kring solens närmsta granne, Proxima Centauri. Exoplaneten upptäcktes nyligen med en jämviktstemperatur under $0\degree$C. Trots att exoplaneten inte anses beboelig enligt klassisk definition kan det finnas delar av Proxima Centauri b som är beboeliga. En tidigare studie simulerade klimatförhållandena av Proxima Centarui b till jämvikt nåddes, med varierade begynnelsetillstånd. I detta projekt beräknas andelen av Proxima Centauri b som är beboelig genom flera olika mått för "fractional habitability". Måtten jämförs med den tidigare studien och dess simuleringar. Grafiskt åsikdligörs resultaten via färgkartor över planeten för istjocklek och yttemperatur. De beräknade värdena på Proxima Centauri b's "fractional habitability" påvisar beroende på mått och begynnelsetillstånd. Däremot, för en majoritet av både fall och mått är värdet nollskilt vilket antyder att Proxima Centauri b är delvist beboelig.
3
Shalam, Moinuddin Khaja. "Parallelization of a quasi-3D nearshore circulation model." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-07092004-121009.
Full text
4
Dugas, Bernard. "Persistent circulation anomalies in observations and in a general circulation model." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74220.
Full textAbstract:
A comparative diagnostic study of upper-air persistent atmospheric events, as simulated by a general circulation model (GCM) and as observed, is presented. We start with an overview of the several theories that attempt to explain such phenomena. Particular emphasis is put on the model approach of Shutts (1983). We next show that the spatial distributions of persistent events is qualitatively similar in the GCM and observational data. The North-Atlantic events are extracted and a rotated empirical orthogonal function (REOF) analysis is done on the resulting data sets. The two REOF sets that are thus obtained are shown to greatly resemble one another. Both explain roughly 50% of their original data's variance. The relationships between the modes within a set are presented, so as to understand their probable combined evolution. The fourth chapter contains an evaluation of Shutt's theory. There, the third chapter's results are used to isolate a particular class of events, namely the strong +ATL2 dipoles. The time-tendencies associated to short time-scale synoptic waves are evaluated, using an E-vectors approach, taking care to distinguish between the onset, mature and demise phases of the events. It seems that these synoptic waves have a significant impact of the average life-cycle of this +ATL2 type of events, whether they be simulated by a GCM or obtained from a NMC set of analyses.
5
Peters, Bevis Michael. "A Martian thermosphere : ionosphere general circulation model." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271688.
Full text
6
Chattopadhyay, Mohar. "Gravity wave parameterization in the general circulation model." Thesis, University of Canterbury. Physics and Astronomy, 2003. http://hdl.handle.net/10092/6065.
Full textAbstract:
Although there is a rich literature on modelling the effects of broad spectrum gravity waves (GW) in General circulation Models (GCM), the effect of a coupled interactive broad spectrum and monochromatic GW has not been studied in detail. Such a study is of paramount importance as it could conclusively demonstrate that the coupled interactive broad spectrum and monochromatic GW can be parameterized in a GCM and its effects on atmospheric circulations can be studied.
The main objective of this thesis is to investigate how the climate simulated by the Unified Model (UM), a state-of-the-art GCM, responds to more physically realistic gravity wave parameterizations, beginning with the addition of a spectral gravity wave scheme, and then progressing to a scheme which couples both orographic and spectral gravity waves.
Behaviour of the schemes are analyzed using a set of four idealized experiments in a single column test-bed based on the architecture of the UM. Results from these experiments are discussed before implementing the schemes in the UM. These findings provide the necessary backdrop around which more complex interactions modelled by the UM are discussed.
The UM is run for six years with the two GW schemes. Monthly means of a range of diagnostic fields results are compared qualitatively with the U.K. Met. Office global assimilated data. Both schemes simulate the overall structure of the atmospheric circulation. The simulations based on the two GW schemes are also compared against each other to observe any potential effect on the climatology of the UM due to their different underlying assumptions. The results show sensitivity of the model in the dynamics of middle atmosphere. Some degree of variability is also exhibited in tropospheric circulation. A major conclusion that emerges from the extension of the spectral gravity wave scheme to the coupled interactive scheme is that the latter is equivalent to a change in the global mean gravity wave strength.
7
Gehlot, Swati, and Johannes Quaas. "Convection–climate feedbacks in the ECHAM5 general circulation model." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177611.
Full textAbstract:
A process-oriented climate model evaluation is presented, applying the International Satellite Cloud Climatology Project (ISCCP) simulator to pinpoint deficiencies related to the cloud processes in the
ECHAM5general circulation model.ALagrangian trajectory analysis is performed to track the transitions of anvil cirrus originating from deep convective detrainment to cirrostratus and thin cirrus, comparing ISCCP observations and the ECHAM5 model. Trajectories of cloudy air parcels originating from deep convection are computed for both, the ISCCP observations and the model, over which the ISCCP joint histograms are used for analyzing the cirrus life cycle over 5 days. The cirrostratus and cirrus clouds originate from detrainment from deep convection decay and gradually thin out after the convective event over 3–4 days. The effect of the convection–cirrus transitions in a warmer climate is analyzed in order to understand the climate feedbacks due to deep convective cloud transitions. An idealized climate change simulation is performed using a+2-K sea surface temperature (SST) perturbation. The Lagrangian trajectory analysis over perturbed climate suggests that more and thicker cirrostratus and cirrus clouds occur in the warmer climate compared to the present-day climate. Stronger convection is noticed in the perturbed climate, which leads to an increased precipitation, especially on day -2 and -3 after the individual convective events. The shortwave and the longwave cloud forcings both increase in the warmer climate, with an increase of net cloud radiative forcing (NCRF), leading to an overall positive feedback of the increased cirrostratus and cirrus clouds from
a Lagrangian transition perspective.
8
Privé, Nikki C. 1977. "Zonally symmetric monsoon dynamics in a general circulation model." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/59100.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002.Includes bibliographical references (p. 97-98).
The MIT general circulation model is used with simplified setup to study steady zonally averaged monsoon circulations. Two dimensional model runs are made with a zonally symmetric continent north of 15N and a slab ocean of uniform sea surface temperature to study the applicability of axisymmetric theory. Forcing to drive the monsoon is applied by heating the subtropical land surface. The dynamical constraints of axisymmetry prevent low-level cross-equatorial flow and inhibit the northward transport of moisture onto the continent when there is no temperature gradient across the equator. The ocean cannot supply adequate moisture to feed the monsoon, and the ground hydrology strictly controls the behavior of the monsoon. A second set of two dimensional runs with similar continent, but with an SST gradient across the equator, result in a viable steady monsoon with low-level cross-equatorial flow providing moisture to the monsoon. The surface forcing required to induce a monsoon is reasonable given the constraints of the axisymmetric model setup. A series of three dimensional model runs with a zonally symmetric continent are made to study the role of zonally asymmetric flow on the zonal mean monsoon. It is found that greater land surface forcing is required to induce a zonally averaged monsoon circulation in the three dimensional runs than in similar axisymmetric runs. The behavior of the monsoon disturbances in the three dimensional runs is similar to the observed Asian monsoon in that there is low-level cross-equatorial flow which is southwesterly along the coastline, and in that a large-scale angular momentum conserving meridional circulation develops with ascent over the continent and subsidence in the opposite hemisphere. Moisture transport is found to play a very strong role in the monsoon dynamics in all of the model runs.
by Nikki C. Privé.
S.M.
9
Mendonca, Joao M. "Studies of Venus using a comprehensive general circulation model." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:eab33b95-b66a-4d10-8696-548e1d211c9f.
Full textAbstract:
The profusion of observational data made available by the Venus Express and previous space missions, increases our need to develop numerical tools to interpret the data and improve our understanding of the Venus meteorology. The main objective of this work is to develop an improved Venus general circulation model and to study the most likely mechanisms driving the atmosphere to the current observed circulation. Our new model is an extension of a simplified version and includes a new radiative transfer scheme and convection and an adapted boundary layer scheme and dynamical core that take into account the dependence of the heat capacity with temperature, at constant atmospheric pressure. The new radiative transfer formulation implemented is more suitable for Venus climate studies than previous works due to its easy adaptability to different atmospheric conditions. This flexibility of the model was very important in this work to explore the uncertainties on the lower atmospheric conditions such as the gas absorption and the possible presence of aerosols near the surface. The new general circulation model obtains, after long periods of integration, a super-rotation phenomenon in the cloud region quantitatively similar to the one observed. However, this phenomenon is sensitive to some radiative parameters such as the amount of the solar radiative energy absorbed by the surface and the amount of clouds. The super-rotation in the model is formed due to the combined influence of the zonal mean circulation, thermal tides and transient waves, and the main mechanisms involved are identified and studied. In this process the momentum transported by the semidiurnal tide excited in the upper clouds has a key contribution. These migrating waves transport prograde momentum mainly from the upper atmosphere to the cloud region. In this work we also explored the model parameters to gain a better understanding of the effect of topography, the diurnal cycle and convective momentum mixing. In general the results showed that: the topography seemed capable of sustaining stronger global super-rotation; without diurnal cycle the strong winds in the cloud region are not produced; the convective momentum mixing experiment did not lead to significant changes. A simple experiment done advecting the UV absorber in the atmosphere, qualitatively showed several atmospheric phenomena that are important for the distribution of clouds. Among them is the presence of a region of low permeability isolating the polar vortex. This last experiment also showed that when increasing the amount of UV absorption in the upper cloud region the winds get stronger. Following the interpretation of observational data using numerical models, we also used a simplified version of the general circulation model to assess the accuracy of zonal wind retrievals from measured temperatures using the cyclostrophic thermal wind equation in the Venus mesosphere. From this analysis we suggest a method which better estimates the lower boundary condition, and improves the consistency of the results at high latitudes when compared with cloud tracking measurements.
10
Su, Lin 1966. "A diagnostic study of the summer southern hemisphere circulation of the CCC general circulation model /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60493.
Full textAbstract:
The medium scale planetary wave regime, consisting largely of zonal wavenumbers 5-7, frequently dominate the summer Southern Hemisphere tropospheric circulation. We perform a diagnostic study of this circulation as simulated by the Canadian Climate Centre (CCC) general circulation model (GCM). The analysis of Hovmoller diagrams, space-time and zonal wavenumber spectra shows that the CCC GCM is able to simulate the observed medium scale wave regime.The zonally averaged meridional eddy heat and momentum transports and the associated baroclinic and barotropic energy conversions are also examined. The distributions of the transports on the vertical plane agree well with observations. When compared to the observed summer 1979 distributions, some quantitative differences remain: the vertical structure of the heat transport is too baroclinic, while the momentum transport tends to be too weak. The baroclinic and barotropic conversions all show a medium scale wave signal. The time evolution of the Richardson number of the mean flow suggests that the medium scale wave is due to a finite amplitude baroclinic instability.
11
Vettoretti, Guido. "Paleoclimate tests of a model of the atmospheric general circulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63759.pdf.
Full text
12
Beare, Matthew Ivor. "The development of a general purpose parallel ocean circulation model." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266748.
Full text
13
Saito, Ryu. "Influence of the surface on the atmospheric circulation of Mars : study with a general circulation model /." Katlenburg-Lindau : Copernicus, 2007. http://www.gbv.de/dms/bs/toc/535034385.pdf.
Full text
14
Robitaille, Daniel Y. "On the use of CFCs in an oceanic general circulation model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32677.pdf.
Full text
15
Mullen, Steven Lee. "On the maintenance of blocking anticyclones in a general circulation model /." Thesis, Connect to this title online; UW restricted, 1985. http://hdl.handle.net/1773/10094.
Full text
16
Schirber, Sebastian, Daniel Klocke, Robert Pincus, Johannes Quaas, and Jeffrey L. Anderson. "Parameter estimation using data assimilation in an atmospheric general circulation model." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177507.
Full textAbstract:
This study explores the viability of parameter estimation in the comprehensive general circulation model ECHAM6 using ensemble Kalman filter data assimilation techniques. Four closure parameters of the cumulus-convection scheme are estimated using increasingly less idealized scenarios ranging from perfect-model experiments to
the assimilation of conventional observations. Updated parameter values from experiments with real observations are used to assess the error of the model state on short 6 h forecasts and on climatological timescales. All parameters converge to their
default values in single parameter perfect-model experiments. Estimating parameters simultaneously has a neutral effect on the success of the parameter estimation, but applying an imperfect model deteriorates the assimilation performance. With real observations, single parameter estimation generates the default parameter value in one case, converges to different parameter values in two cases, and diverges in the fourth case. The implementation of the two converging parameters influences the model state: Although the estimated parameter values lead to an overall error reduction on short timescales, the error of the model state increases on climatological timescales.
17
Haywood, Alan M. "Evaluating general circulation climate model reliability with the Pliocene geological record." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271189.
Full text
18
Yagai, Isamu. "NUMERICAL SIMULATION OF ATMOSPHERIC THERMAL TIDES WITH A GENERAL CIRCULATION MODEL." Kyoto University, 1991. http://hdl.handle.net/2433/168744.
Full textAbstract:
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・論文博士
博士(工学)
乙第7629号
論工博第2514号
新制||工||853(附属図書館)
UT51-91-T435
(主査)教授 加藤 進, 教授 深尾 昌一郎, 教授 桜井 健郎
学位規則第4条第2項該当
19
Sagoo, Navjit. "Warm equable palaeoclimates, the role of general circulation model uncertainty in model-data mismatch." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684755.
Full textAbstract:
Geological data for past extremely warm climates such as the early Eocene and the late Jurrasic indicate extensive global warming, with very warm temperatures at both poles. However, despite numerous attempts to simulate this warmth, there are remarkable datamodel differences in the prediction of these polar surface temperatures, resulting in the so called "equable climate problem". This work explores how climate model uncertainty may contribute to the simulation of equable climates. A number of simulations are conducted for the Eocene and the Late Jurassic climates, including perturbed physics ensembles (PPEs) for both time periods. Uncertain climate-sensitive parameters are perturbed in these PPEs in order to understand the range of climates that can be simulated with these methods. Simulations investigating the sensitivity of the Late Jurassic climate to uncertain boundary conditions (C02 concentrations; orbital configuration; orography and soil properties) have also been carried out. The Eocene and Jurassic PPEs simulate the most equable climates. Whilst the perturbed soil and orography simulations have a smaller climate response than the PPE simulations and are too cold compared to the proxy data. One early Eocene PPE simulation shows a good match with the available proxy data and has a large polar amplification. This well performing Eocene simulation also simulates the present day climate well and has a low value of climate sensitivity. The same parameter set also simulates the Late Jurassic climate well when compared with proxy data. The Late Jurassic PPE has a smaller range of climates than the Eocene PPE and most simulations in the Late Jurassic PPE have a good match with the proxy data. Variation in the Eocene PPE appears to be driven by differences in cloud properties which are a large source of uncertainty in constraining present day climate forcing The main findings of this work indicate that perturbed parameter ensembles (PPEs) for global palaeoclimate could play an important role in improving both palaeoclimate and present day simulations
20
Nitsche, Gregor. "Some aspects of planetary-scale atmospheric variability in a low-resolution general circulation model /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10014.
Full text
21
Jin, Jiming. "A physically-based snow model coupled to a general circulation model for hydro-climatological studies." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/289782.
Full textAbstract:
A Snow-Atmosphere-Soil Transfer (SAST) model has been developed to extend the point snowmelt model to vegetated areas using the parameterization concepts of the Biosphere-Atmosphere Transfer Scheme (Dickinson et al. 1993). The model applications for short-grass and forest fields show that the simulated surface temperature, albedo, and snow depth have close agreement with observations. In addition, because of biases in simulated runoff in the high-latitudes, a Shuffled Complex Evolution (Sorooshian et al. 1993) scheme for automatic calibration has been connected with the SAST model to determine the realistic distribution of runoff components from different soil layers and search the optimized parameter set. The calibrated runoff closely matches observations. Because the Community Climate Model version 3 (CCM3) coupled with the SAST model overestimates snow depth and precipitation and underestimates surface temperature over the Rocky Mountains, remotely sensed snow depth data have been assimilated in the model to alleviate model discrepancies based on energy and mass balances. The improved surface temperature simulations result from the decreased snowmelt and albedo in winter and spring and from the weakened evaporation in summer due to drier soil. Meanwhile, modeled summer precipitation over the Rocky Mountains has a minor improvement. The relationship between the variations of tropical Pacific SST and snowpack anomalies in the western United States (U.S.) has been studied by comparing observations and CCM3 output. The results indicate that in the northwestern U.S., the warm tropical Pacific phase of the El Nino-Southern Oscillation (ENSO) is associated with diminished snowpack while its cool phase is related to enhanced snowpack. This relationship is largely determined by winter precipitation variability for the observations; however, it relies heavily on the variations of temperature due to the biases in atmospheric patterns for the model output. In the southwestern U.S., positive snowpack anomalies for both observations and simulations result from the strong warm phase of the ENSO and negative ones are connected with exaggerated local precipitation in fall.
22
Aider, Rabah. "Skill of monthly and seasonal forecasts using a Canadian general circulation model." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32296.
Full textAbstract:
An analysis of the co-variability of surface air temperature and precipitation over North America and Pacific SST is conducted using an SVD analysis. The leading SVD mode revealed a strong link between November SST anomalies and winter surface air temperature (SAT) and precipitation anomalies. In summer this relationship is much weaker. In winter GCM3 captured well the Pacific SST forcing and its response, particularly on the SAT pattern, but its response is less accurate in the summer. The monthly and seasonal forecasts using GCM3 are also analyzed. Precipitation forecasts showed little skill, especially in the warm season where the SST forcing is weak. Furthermore, GCM3 has low seasonal predictive skill in forecasting drought events over the Canadian prairies. However, the model has generally good predictive skill for 500 hPa heights and SAT, with higher scores in the winter. The skill is concentrated in the first month of the prediction period and decreases as the lead time is extended to one month.Une analyse de la co-variabilité entre la température de l'air au sol (SAT) ainsi que les précipitations en Amérique du Nord et la température de l'océan Pacifique à la surface (SST), a été faite en utilisant la méthode SVD. Le mode dominant de la SVD a révélé une relation forte entre les anomalies de la SST du mois de novembre et celles de la SAT et des précipitations hivernales. Ce lien est beaucoup plus faible en été. Le modèle GCM3 reproduit assez bien la réponse au forçage de la SST, particulièrement sur les patrons de la SAT, mais sa réponse est beaucoup moins précise en été. Les prévisions mensuelles et saisonnières de GCM3 ont aussi été analysées. Les capacités de GCM3 à prévoir les précipitations sont faibles, surtout en été où le forçage de la SST est aussi faible. De plus, le modèle ne possède pas d'habiletés notables à prédire les sécheresses dans les prairies Canadiennes. Par contre, les capacités prévisionnelles du modèle concernant la SAT et le géopotentiel à 500 hPa sont généralement assez élevées, particulièrement en hivers. Les habiletés de GCM3 sont concentrées dans le premier mois de la période de prévision, puis déclinent lorsque le délai d'émission est prolongé.
23
Brown, Catherine Alicia. "Oscillatory behavior in an ocean general circulation model of the North Atlantic." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/MQ46006.pdf.
Full text
24
Shongwe, Mxolisi Excellent. "Performance of recalibration systems of general circulation model forecasts over southern Africa." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-07032007-102650.
Full text
25
Weaver, Anthony T. "On assimilating sea surface temperature data into an ocean general circulation model." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29204.
Full textAbstract:
The feasibility of sea surface temperature (SST) data improving the performance of an ocean general circulation model (OGCM) is investigated through a series of idealized numerical experiments. The GFDL Bryan-Cox-Semtner primitive equation model is set-up as an eddy resolving, unforced, flat bottomed channel of uniform depth. 'Observed'
SST data taken from a reference ocean established in a control run are continuously
assimilated into an 'imperfect' model using a simple 'nudging' scheme based on a surface relaxation condition of the form Q = C(SST — T₁) where Q is the heat flux and T₁ is the temperature at the top level of the model. The rate of assimilation is controlled by adjusting the constant inverse relaxation time parameter C.
Numerical experiments indicate that the greatest improvement in the model fields is achieved in the extreme case of infinite assimilation (i.e., C = ᅇ) in which the 'observed' SST is directly inserted into the model. This improvement is quantified by monitoring the reduction in the root mean square (RMS) errors relative to the simulated
reference ocean. Assimilation with longer relaxation time-scales (i.e., smaller C's) proves quite ineffective in reducing the RMS errors. The improvement in the direct insertion numerical experiment stems from the model's ability to transfer assimilated SST into subsurface information through strong advective processes. The assimilation of cool surface data induces convective overturning which transfers the 'cool' information
downward rapidly but adversely affects the vertical thermal structure by an unrealistic deepening of the mixed layer. By contrast, warm surface data do not penetrate
downward readily. Thus, the systematically biased downward flux of coolness gradually produces unrealistically cool subsurface waters.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
26
Saito, Ryu [Verfasser]. "Influence of the surface on the atmospheric circulation of Mars : study with a general circulation model / von Ryu Saito." Katlenburg-Lindau : Copernicus GmbH, 2007. http://d-nb.info/994484453/34.
Full text
27
Weddle, Charles A. OCEAN CURRENTS PACIFIC OCEAN OCEAN MODELS WIND STRESS STRESSES MATHEMATICAL MODELS WIND SENSITIVITY DEPTH CIRCULATION TROPICAL CYCLONES LONGITUDE INSTABILITY CYCLONES AIR WATER INTERACTIONS MIXED LAYER(MARINE) IMAGES METEOROLOGICAL SATELLITES THESES EQUATORIAL REGIONS TEMPERATURE. "The effect of westerly wind bursts on a tropical ocean general circulation model /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA276423.
Full textAbstract:
Thesis (M.S. in Meteorology and M.S. in Physical Oceanography) Naval Postgraduate School, December 1993.Thesis advisor(s): Murphree, James Thomas ; Garwood, Roland W. "December 1993." Bibliography: p. 115-118. Also available online.
28
Weddle, Charles A., and CURRENTS PACIFIC OCEAN OCEAN MODELS WIND STRESS STRESSES MATHEMATICAL MODELS WIND SENSITIVITY DEPTH CIRCULATION TROPICAL CYCLONES LONGITUDE INSTABILITY CYCLONES AIR WATER INTERACTIONS MIXED LAYER(MARINE) IMAGES ME OCEAN. "The effect of westerly wind bursts on a tropical ocean general circulation model." Thesis, Monterey, California. Naval Postgraduate School, 1993. http://hdl.handle.net/10945/26516.
Full textAbstract:
A primitive equation general circulation model with imbedded mixed layer physics has been used to investigate the response of the equatorial Pacific ocean to daily varying winds and westerly wind bursts. The major issue addressed by this study is the impact of daily varying winds, including westerly wind bursts, in the modeling of the tropical Pacific ocean and El Nino. In the developmental phase, the sensitivity of the model to the integration time step and the domain size were investigated. The results of this work were used to determine the optimal time step and model domain size for the main experimental model runs. In the experimental phase, the model was spun-up using time averaged wind stresses. The model ocean was then exposed to two years of realistic daily varying wind stresses covering the period of 1991 and 1992. The model developed an El Nino like response that corresponded in several respects with observed features of the 1991-92 El Nino. The model also developed tropical instability waves in the eastern Pacific similar to those observed in situ and in satellite SST images. The model's responses to the tropical cyclones that occurred during 1991-92 were also consistent in several ways with observations
29
Liu, Fei. "A sensitivity study of a general circulation model with enhanced shortwave atmospheric absorption." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068182.
Full text
30
Gong, Gavin 1969. "The role of fractional rainfall coverage in atmospheric general circulation model hydrologic processes." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35428.
Full text
31
Won, Eric C. "Sensitivity of a general circulation inverse model to sub-grid scale parametrization coefficients." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/58432.
Full text
32
Scott, Russell Lawrence. "Effect of land surface formulation on climate variability within a general circulation model." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17397.
Full text
33
Chakraborty, Arindam. "Impact of Orography on the Simulation of Monsoon Climate in a General Circulation Model." Thesis, Indian Institute of Science, 2004. http://hdl.handle.net/2005/76.
Full textAbstract:
Orography plays a major role in the general circulation and climate of the tropics. Although many works have been done on the impact of global orography on summer monsoon, the previous studies have examined the impact on seasonal mean scale or only during the first half of the season. Role of orography on intra-seasonal variability has not been addressed previously. Also, the proximate and remote impacts of orography have not been studied. In this thesis an atmospheric General Circulation Model (GCM) has been used to investigate the impact of global and regional orography on monsoon climate. Two different cumulus schemes have been used to study the sensitivity of the results to the cumulus parameterization scheme. The model was forced with seasonally varying sea surface temperature (SST) for the year 1998. An ensemble simulation of 5 members were performed for each experiment.
The simulations showed that the removal of Himalayas or orography over the entire earth caused a delay of about one month in the onset of the monsoon. The delay in monsoon onset was on account of a more stable atmosphere due to intrusion of mid-latitude cold air into the Indian region in the absence of Himalayas. After the onset, the precipitation rate was comparable in control and no-mountain simulations. The seasonal mean (June-September) precipitation over this region decreased by 25% in the no-mountain case as compared to control.
A comparison of the impact of east and west Himalaya orography showed that orography west of 80E has more impact on the phase and intensity of summer monsoon precipitation over the Indian region than orography east of 80E. The onset of summer monsoon over the Indian region was delayed by about one month with the removal of Himalaya orography west of 80E, but was delayed by just about one week with the removal of Himalaya orography east of 80E. This is because, the cold air intrusion was more when Himalaya orography west of 80E was removed. Seasonal mean precipitation decreased by 22% and 12% with the removal of orography west and east of 80E respectively. Himalaya orography east of 80E showed more influence on precipitation over the north-east Indian region and East Asia.
The removal of orography from the African continent increased the summer monsoon precipitation over the Indian region. This was on account of an increase in the zonal mass flux from the African continent in the absence of East African mountains. This mass flux brings more moisture into the south Asian region and increases precipitation over the Indian region and Bay of Bengal. A higher precipitation over the Bay of Bengal leads to higher wind over the Somalia coast and this acts as a positive feedback to enhance the summer monsoon precipitation by about 28% over the Indian region.
The presence of orography only over the African continent resulted in the largest delay in the monsoon onset (by 50 days) and the lowest amount of seasonal precipitation (decrease by 36%) over the Indian region among all the simulations. This is due to further reduction in zonal mass (and hence, moisture) flux toward the Indian subcontinent with the inclusion of African orography when compared with no-global orography simulation.
The seasonal mean precipitation decreased by 19% over the Indian region with the removal of American orography. The onset of monsoon was delayed by about 3 weeks in this experiment as compared to control. This delay was due to a relative downward motion in the upper troposphere on account of the shift of the Rossby wave with the removal of American mountains.
In this thesis, a new theory has been proposed for monsoon onset based on thermodynamic conditioning (necessary condition) and mechanical trigger (sufficient condition) of the atmosphere. This theory was able to explain the large variation in monsoon onset dates (maximum spread 57 days) in different simulations.
The low level circulation was affected more by Himalaya orography west of 80E, which had a profound influence on precipitation over the Indian region. However, upper level circulation was affected more by Himalaya orography east of 80 E. The northward shift of the upper tropospheric westerly jet during the Northern Hemispheric summer was sudden in presence of the Tibetan Plateau and gradual in its absence. This shift was not related to the onset of monsoon over the Indian region.
Northward propagation of convection was found to be present even in the absence of global orography. But northward extent of this propagation was delayed without orography on account of the absence of a favorite meridional gradient of moist static energy in the lower troposphere in the early summer season due to intrusion of mid-latitude cold air. Space-time spectral analysis showed that the intensity of eastward moving convectively coupled atmospheric waves, known as Madden-Julian oscillation (MJO), decreased in absence of global orography. Moreover, the presence of orography favor the higher zonal wave number for MJO propagation.
34
Agarwal, Reema [Verfasser], and Detlef [Akademischer Betreuer] Stammer. "Improving an Atmosphere General Circulation model through Parameter Optimization / Reema Agarwal ; Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/1124591206/34.
Full text
35
Buchholz, Joachim. "Simulations of physics and chemistry of polar stratospheric clouds with a general circulation model." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976096129.
Full text
36
Ring, Michael J. 1979. "Annular mode-like responses to external forcings in a simple atmospheric general circulation model." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43152.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.Includes bibliographical references (p. 217-225).
In this thesis, I investigate the response of a simple atmospheric general circulation model to applied forcings to learn whether the annular mode patterns are a preferred model response to the forcings. The thesis is inspired by the appearance of annular mode patterns in Earth's atmosphere in response to a number of forcings. Climatologies of the model under the influence of applied torques or perturbations to the reference temperature profile are compiled and compared to a control run with neither type of forcing. In most cases the differences in climatologies are annular mode-like, suggesting the patterns are the preferred response of the model to the forcings. The strength of the response typically increases for either an increase in the strength of the forcing, or an increase in the strength of the projection of the forcing on the model's annular mode patterns. Trials with a response which was not annular mode-like usually featured a poor projection of the forcing on the annular modes, or substantial interference with tropical dynamics. A zonally symmetric version of the model is also used to test the direct response of the model to the forcing versus the response caused by changes in eddy feedback processes. The direct forcing alone is found to be insufficient to produce either the correct strength or shape of the annular mode patterns. Instead the changes in eddy fluxes must be included to produce the correct shape and amplitude of the anomalies.
by Michael John Ring.
Ph.D.
37
Bakker, P., A. Schmittner, J. T. M. Lenaerts, A. Abe-Ouchi, D. Bi, den Broeke M. R. van, W. L. Chan, et al. "Fate of the Atlantic Meridional Overturning Circulation: Strong decline under continued warming and Greenland melting." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/622754.
Full textAbstract:
The most recent Intergovernmental Panel on Climate Change assessment report concludes that the Atlantic Meridional Overturning Circulation (AMOC) could weaken substantially but is very unlikely to collapse in the 21st century. However, the assessment largely neglected Greenland Ice Sheet (GrIS) mass loss, lacked a comprehensive uncertainty analysis, and was limited to the 21st century. Here in a community effort, improved estimates of GrIS mass loss are included in multicentennial projections using eight state-of-the-science climate models, and an AMOC emulator is used to provide a probabilistic uncertainty assessment. We find that GrIS melting affects AMOC projections, even though it is of secondary importance. By years 2090-2100, the AMOC weakens by 18% [-3%, -34%; 90% probability] in an intermediate greenhouse-gas mitigation scenario and by 37% [-15%, -65%] under continued high emissions. Afterward, it stabilizes in the former but continues to decline in the latter to -74% [+4%, -100%] by 2290-2300, with a 44% likelihood of an AMOC collapse. This result suggests that an AMOC collapse can be avoided by CO2 mitigation.
38
Gough, William A. (William Arthur). "Lateral and isopycnal mixing of passive and active tracers in an ocean general circulation model." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70297.
Full textAbstract:
The parameterization of isopycnal mixing is examined in an ocean general circulation model. The results are compared to those obtained with lateral mixing.In the equilibrium experiments, the isopycnal case has more gyre kinetic energy, a less intense thermohaline circulation, and less interior downwelling than the lateral case. Convection is replaced by enhanced vertical diffusion in the isopycnal case.
In the time dependent passive tracer experiments, the isopycnal case has smaller depth penetration of a surface released tracer. This is likely due to induced recirculation rather than numerical limitations.
The active tracer experiments examine the long term asymmetric behaviour of warm and cold surface anomalies introduced in an abrupt and gradual fashion for the lateral and isopycnal models. The thermal anomalies produce asymmetric transient responses. The abrupt and gradual changes produce the same equilibrium but different transient responses. The isopycnal case responds more rapidly and energetically than the lateral case.
39
Xiaohan, Liao. "Two general circulation model experiments for 6000 years B.P. : analyses and comparisons with palaeoclimatic data." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333247.
Full text
40
Demory, Marie-Estelle. "Sensitivity of the global hydrological cycle to horizontal resolution in an atmospheric general circulation model." Thesis, University of Reading, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654493.
Full text
41
West, Rosalind Eleanor Lunzer. "Estimation of the indirect radiative effects of aerosol on climate using a general circulation model." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:bc1cc003-cf96-4b27-aad9-75ef7045dfc3.
Full textAbstract:
The indirect effects of anthropogenic aerosols—through their interactions with clouds—are currently one of the most uncertain perturbations to the radiative energy balance at the top of the atmosphere. A crucial link between aerosol and cloud is that aerosols can act as cloud condensation nuclei (CCN). This microphysical process must be parameterised if the large-scale effects are to be represented in a general circulation model (GCM). Theoretical work presented in this thesis highlights the importance of incorporating the kinetic limitations on droplet formation in aerosol activation parameterisations. HadGEM-UKCA is a GCM, capable of representing the chemical and microphysical aerosol processes required to model CCN accurately. The author has incorporated a Köhler theory based parameterisation of aerosol activation into HadGEM-UKCA, to facilitate quantitative predictions of the indirect aerosol effects. This thesis presents an estimate of the range of uncertainty in such predictions attributable to the choice of parameterisation of the sub-grid-scale variability of vertical velocity. Results of simulations demonstrate that the use of a characteristic updraught velocity cannot replicate results derived with a distribution of vertical velocities, and is to be discouraged in GCMs. Consequently, work focuses on the effect of the variance (σw2) of a Gaussian pdf of vertical velocity. Fixed values of σw and a configuration in which σw depends on turbulent kinetic energy are tested. Results from the mid-range fixed σw and TKE-based configurations both compare well with vertical velocity distributions and cloud droplet number concentrations measured in situ. However, the sparse set of available measurements does not provide enough of a constraint to recommend one or the other as the best configuration globally. The radiative flux perturbation (RFP) due to the total effects of anthropogenic aerosol is estimated at −1.7Wm−2 for the TKE-based configuration. To the extent that it is valid to decouple the individual aerosol effects, the direct effect accounts for approximately −0.6Wm−2 of the total, the cloud albedo effect −0.8Wm−2 and the cloud lifetime effect −0.3Wm−2, indicating that these effects are additive within HadGEM-UKCA. Total aerosol RFP ranges from −1.4Wm−2 from simulations with σw=0.1ms−1, up to −2.0Wm−2 for σw=0.7ms−1. This range of 0.6Wm−2 corresponds to almost a third of the total estimate of −1.9Wm−2, obtained with the mid-range value of σw=0.4ms−1. Reducing the uncertainty in the parameterisation of σw is therefore an important step towards reducing the uncertainty in estimates of the indirect aerosol effects.
42
Grezio, Anita. "The dynamical controls on the Antarctic Circumpolar Current with the use of general circulation model." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395958.
Full text
43
Nam, Christine C. W., and Johannes Quaas. "Geographically versus dynamically defined boundary layer cloud regimes and their use to evaluate general circulation model cloud parameterizations: Geographically versus dynamically defined boundary layer cloudregimes and their use to evaluate general circulation model cloud parameterizations." American Geophysical Union (AGU), 2013. https://ul.qucosa.de/id/qucosa%3A13460.
Full textAbstract:
Regimes of tropical low-level clouds are commonly identified according to large-scale subsidence and lower tropospheric
stability (LTS). This definition alone is insufficient for the distinction between regimes and limits the comparison of low-level clouds from CloudSat radar observations and the ECHAM5 GCM run with the COSP radar simulator. Comparisons of CloudSat radar cloud altitude-reflectivity histograms for stratocumulus and shallow cumulus regimes,
as defined above, show nearly identical reflectivity profiles,
because the distinction between the two regimes is dependent
upon atmospheric stability below 700 hPa and observations above 1.5 km. Regional subsets, near California and Hawaii, for example, have large differences in reflectivity profiles than the dynamically defined domain; indicating different reflectivity profiles exist under a given
large-scale environment. Regional subsets are better for the
evaluation of low-level clouds in CloudSat and ECHAM5 as there is less contamination between 2.5 km and 7.5 km from precipitating hydrometeors which obscured cloud reflectivities.
44
Warrior, Hari. "Parameterization of the Light Models in Various General Ocean Circulation Models for shallow waters." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1292.
Full textAbstract:
Solar energy is incident on the earth's surface in both short-wave and long-wave parts of the spectrum. The short-wave part of the spectrum is of special interest to oceanographers since the vertical distribution of temperature in the top layer of the ocean is mostly determined by the vertical attenuation of short-wave radiation. There are numerous studies regarding the temperature evolution as a function of time (see Chapter 2 for details). The diurnal and seasonal variation of the heat content (and hence temperature) of the ocean is explored in this thesis. The basis for such heat budget simulation lies in the fact that the heat budget is the primary driver of ocean currents (maybe secondary to wind effects) and these circulation features affect the biological and chemical effects of that region.
The vertical attenuation of light (classified to be in the 300-700 nm range) in the top layer of the ocean has been parameterized by several authors. Simpson and Dickey (1981) in their paper have listed the various attenuation schemes in use till then. This includes a single-exponential form, a bimodal exponential form, and a spectral decomposition into nine spectral bands, each with their specific exponential functions with depth.
The effects of vertical light attenuation have been investigated by integrating the light models into a 1D and a 3D turbulence closure model. The main part of the thesis is the inclusion of a bottom effect in the shallow waters. Bottom serves two purposes, it reflects some light based on its albedo and it radiates the rest of the light as heat. 1-D simulation including bottom effects clearly indicates the effect of light on the temperature profile and also the corresponding effect on salinity profiles.
An extension of the study includes a 3D simulation of the heat budget and the associated circulation and hydrodynamics. Intense heating due to the bottom leads to the formation of hyper-saline waters that percolate down to depths of 50 m in the summer. Such plumes have been simulated by using a 3D numerical ocean model and it is consistent with observations from the Bahamas banks.
45
Schirber, Sebastian, Daniel Klocke, Robert Pincus, Johannes Quaas, and Jeffrey L. Anderson. "Parameter estimation using data assimilation in an atmospheric general circulation model: Parameter estimation using data assimilation in an atmosphericgeneral circulation model: from a perfect toward the real world." American Geophysical Union (AGU), 2013. https://ul.qucosa.de/id/qucosa%3A13463.
Full textAbstract:
This study explores the viability of parameter estimation in the comprehensive general circulation model ECHAM6 using ensemble Kalman filter data assimilation techniques. Four closure parameters of the cumulus-convection scheme are estimated using increasingly less idealized scenarios ranging from perfect-model experiments to
the assimilation of conventional observations. Updated parameter values from experiments with real observations are used to assess the error of the model state on short 6 h forecasts and on climatological timescales. All parameters converge to their
default values in single parameter perfect-model experiments. Estimating parameters simultaneously has a neutral effect on the success of the parameter estimation, but applying an imperfect model deteriorates the assimilation performance. With real observations, single parameter estimation generates the default parameter value in one case, converges to different parameter values in two cases, and diverges in the fourth case. The implementation of the two converging parameters influences the model state: Although the estimated parameter values lead to an overall error reduction on short timescales, the error of the model state increases on climatological timescales.
46
Kim, Joong Tae. "Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5746.
Full textAbstract:
Open water in sea ice, such as leads and polynyas, plays a crucial
role in determining the formation of deep- and bottom-water, as well
as their long-term global properties and circulation. Ocean general
circulation models (GCMs) designed for studies of the long-term
thermohaline circulation have typically coarse resolution, making it
inevitable to parameterize subgrid-scale features such as leads and
convective plumes. In this study, a hierarchy of higher-resolution
sea-ice models is developed to reduce uncertainties due to coarse
resolution, while keeping the ocean component at coarse resolution to
maintain the efficiency of the GCM to study the long-term deep-ocean
properties and circulation. The higher-resolved sea-ice component is restricted to the Southern Ocean. Compared with the coarse sea-ice
model, the intermediate, higher-resolution version yields more
detailed coastal polynyas, a realistically sharp ice edge, and an
overall enhanced lead fraction. The latter gives enhanced rates of
Antarctic Bottom Water formation through enhanced near-boundary
convection. Sensitivity experiments revealed coastal katabatic winds
accounted for in the higher resolution version, are the main reason
for producing such an effect. For a more realistic coastline,
satellite passive-microwave data for fine-grid land/ice-shelf â seaice/
ocean boundary were used.
With a further enhancement of the resolution of the Southern OceanâÂÂs
sea-ice component, a grid spacing of 22 km is reached. This is about
the size of the pixel resolution of satellite-passive microwave data
from which ice concentration is retrieved. This product is used in
this study to validate the sea-ice component of the global ocean GCM.
The overall performance of the high-resolution sea-ice component is
encouraging, particularly the representation of the crucial coastal polynyas. Enhancing the resolution of the convection parameterization
reduces spurious coarse-grid polynyas. Constraining the upper-ocean
temperature and modifying the plume velocity removes unrealistic
small-scale convection within the ice pack. The observed highfrequency
variability along the ice edge is to some extent captured
by exposing the ice pack to upper-ocean currents that mimic tidal
variability. While these measures improve several characteristics of
the Southern Ocean sea-ice pack, they deteriorate the global deepocean
properties and circulation, calling for further refinements and
tuning to arrive at presently observed conditions.
47
Nicholson, W. P. "Studies of the Martian upper atmosphere with the UCL Mars thermosphere and ionosphere general circulation model." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1310428/.
Full textAbstract:
Simulations of the Martian upper atmosphere have been conducted with ‘MarTIM’, University College London’s Martian thermosphere and ionosphere general circulation model (GCM). MarTIM, a finite difference model, solves the coupled non-linear Navier-Stokes equations of continuity and momentum as well as an energy equation with calculations conducted on a fixed co-rotating grid of variable size in the pressure coordinate system. From its lower boundary of 0.883 Pa (~60 km) to its upper boundary of 9.9×10−8 Pa (~200−350 km), it evaluates the main sources of solar forcing (EUV/UV and IR absorption) while self-consistently determining the composition of four of the major gas species, CO2, N2, CO and O. These four major gases are mutually diffused throughout the model in a typical run. Development of MarTIM includes a consideration of the importance of neutral species diffusion and advection on the thermodynamics of the modelled Martian atmosphere. The influence on the modelled atmosphere of including additional neutral species is investigated. Next, a new infrared heating parameterization has been introduced from background research of detailed non-LTE modelling. This has allowed MarTIM to study thermospheric polar warming features as found in Mars Odyssey accelerometer data. MarTIM’s lower boundary is coupled to the Mars Climate Database (MCD v4.3) developed by the University of Oxford, the Open University and Laboratoire de Météorologie Dynamique. This database of GCM results provides MarTIM a physically self-consistent lower boundary derived from multiple runs of the aforementioned circulation models. Consequently the effects of dust storms, non-migrating tides and the influence of Martian topography are studied by prescription of MarTIM’s lower boundary. MarTIM is also compared against density and temperature measurements derived from SPICAM stellar occultation profiles. Lastly, a new ionospheric code has been developed through collaboration with Laboratoire de Planétologie de Grenoble. This has provided a more sophisticated ionosphere model that solves a one-dimensional kinetic Boltzmann transport equation for the suprathermal population of electrons present in the Martian ionosphere. MarTIM can now self-consistently describe an ionosphere produced by both primary (photoionisation) and secondary ionisation (suprathermal electron propagation). This new ionospheric model has been used to study the variation in secondary ionization efficiency (ratio of secondary to primary ion production) through a large range of seasonal and solar conditions.
48
Turner, Andrew George. "Behaviour of the monsoon-ENSO system in current and future climates of a general circulation model." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434114.
Full text
49
Tran, Giang Thanh. "Developing a multi-level Gaussian process emulator of an Atmospheric General Circulation Model for palaeoclimate modelling." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412553/.
Full textAbstract:
The study of past climates provides a unique opportunity to test our understanding of the Earth system and our confidence in climate models. The nature of this subject requires a fine balance between complexity and efficiency. While comprehensive models can capture the system’s behaviour more realistically, fast but less accurate models are capable of integrating on the long timescale associated with Palaeoclimatology. In this thesis, a statistical approach is proposed to address the limitation of our simple atmospheric module in simulating glacial climates by incorporating a statistical surrogate of a general circulation model of the atmosphere into our Earth system modelling framework, GENIE. To utilise the available model spectrum of different complexities, a multi-level Gaussian Process (GP) emulation technique is proposed to established the link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy-moisture balance model). The method is first demonstrated by emulating a scalar summary quantity. A dimensional reduction technique is then introduced, allowing the high-dimensional model outputs to be emulated as functions of high-dimensional boundary forcing inputs. Even though the two atmospheric models chosen are structurally unrelated, GP emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the emulators of PLASIM’s 2-D surface output fields, are built at a reduced computational cost. The emulated quantities are validated against simulated values, showing that the ensemble-wide behaviour of the spatial fields is well captured. Finally, the emulator of PLASIM’s wind field is incorporated into GENIE, providing an interactive statistical wind field which responds to changes in the bound- ary condition described by the ocean module. While exhibiting certain limitation due to the structural bias in PLASIM’s wind, the new hybrid model introduces additional variations to the over-diffusive spatial outputs of EMBM without incurring a substantial computational cost.
50
Betts, Richard Arthur. "Modelling the influence of the vegetated land surface on climate and climate change." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312335.
Full text