Дисертації з теми "Rainfall extreme"
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1
HELLIES, MATTEO. "Extreme rainfall regime characterization in Sardinia using daily rainfall data." Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266863.
Повний текст джерелаАнотація:
For the design of hydraulic structures for flood conveyance and discharge, or
protection of territory against flood is fundamental the knowledge of the ``extreme
rainfall regime'' in the area where the hydraulic structures must be set up.
Indeed the design flood is commonly evaluated as output of rainfall-runoff models that
receive as input the quantitative description of a rainfall extreme event with a given
exceedance probability.
This dissertation assesses the performance of different statistical approaches in
characterizing extreme rainfall in the island of Sardinia (Italy).
After a detailed review of the theoretical bases of existing methodologies, we compare
the results obtained from the use of:
a) a Generalized Extreme value (GEV) distribution model, and a Two component
Extreme Value (TCEV) distribution model, both applied to yearly maxima of daily
rainfall, and b) a Generalized Pareto (GP) distribution model applied to rainfall
excesses above a properly specified threshold. For the latter purpose, we use the
Multiple Threshold Method (MTM) developed by Deidda(2010), which demonstrate
good performance also in the case of quantized records.
In order to describe the spatial variation of TCEV, GEV and GP model parameters a
regional approach based on homogeneous regions, and two versions of Kriging (a
commonly used geostatistical approach) i.e. ordinary Kriging (OK), and Kriging for
uncertain Data (KUD), are compared.
The obtained results are very promising, pointing towards the use of: a)a GEV
distribution model for yearly rainfall maxima, and a KUD model to describe the spatial
variation of model parameters, and b)a GP model for rainfall excesses and either an OK
or a KUD model for the spatial variation of model parameters. The reason why the OK
and KUD approaches lead to the same results in the GP case, is attributed to the
robustness of the MTM method.
2
Nguyen, Tan Danh. "Regional estimation of extreme rainfall events." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84300.
Повний текст джерелаАнотація:
The first part of the research deals with the estimation of extreme rainfalls for locations where rainfall records are sufficiently available (gaged sites); the second part is concerned with cases where rainfall data are limited (partially-gaged sites); and finally the third part involves the most complex situation where rainfall data are unavailable (ungaged sites).For gaged sites, two methods were developed for estimating the annual extreme (AE) rainfalls based on the simple scaling behaviour of the first three non-central moments (NCMs) of the AE rainfall processes and using the Generalized Extreme Value (GEV) distribution as the parent distribution. The first estimation method was called one-moment (OM) method since it only relied on the first-order NCM of AE rainfall series in the computation of the rainfall quantiles, while the second method was called three-moment (TM) procedure since it used all first three NCMs of AE rainfalls in the estimation of the quantiles.
For partially-gaged and ungaged sites, a new approach to defining rainfall homogeneous regions has been proposed based on the similarity of rainfall occurrences at different raingage stations. In addition, a Principal Component Analysis technique was used to assess the similarity of raingages and to delineate homogeneous regions.
On the basis of the proposed method for identifying rainfall homogeneous regions, two new methods (PG-1 and PG-2) were developed for estimating annual maximum (AM) rainfalls at partially gauged sites. These methods were also based on the scaling properties of AM rainfall series for different durations.
For ungaged sites, three methods (UG-1, UG-2, and NR) were proposed for estimating AM rainfalls. Method UG-1 was based on the NCMs of AM rainfalls at an ungaged site that were computed by direct interpolation of the corresponding NCM values from the gaged sites within the same homogeneous region. Method UG-2 used the pooled data set from all gaged sites in the homogeneous region for this computation. On the other hand, the NR method estimated the NCMs of AM rainfalls for an ungaged site using the regional regression between the first three NCMs and the number of rainfall occurrence (NR) values that were interpolated from the NR values of the gaged sites.
Finally, to assess the uncertainty of extreme rainfall estimates, two new methods (CI-1 and CI-2) were developed for computing the confidence limits (CLs) based on these estimated values. The proposed methods were based on the bootstrap technique and the scaling properties of the NCMs of extreme rainfall series.
3
Smith, Elizabeth. "Bayesian modelling of extreme rainfall data." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424142.
Повний текст джерела
4
Zhou, Chen. "On extreme value statistics : maximum likelihood, portfolio optimization, extremal rainfall, Internet auctions = Over extreme waarden statistiek /." Rotterdam : Erasmus Universiteit, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9789051709124.
Повний текст джерела
5
Langousis, Andreas 1981. "Extreme rainfall intensities and long-term rainfall risk from tropical cyclones." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/47737.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 78-85).
We develop a methodology for the frequency of extreme rainfall intensities caused by tropical cyclones (TCs) in coastal areas. The mean rainfall field associated with a TC with maximum tangential wind speed Vmax, radius of maximum winds Rmax, and translation speed Vmax, is obtained using a physically-based model, whereas rainfall variability at both large scales (from storm to storm) and small scales (due to rainbands and local convection) is modeled statistically. The statistical component is estimated using precipitation radar (PR) data from the TRMM mission. Taylor's hypothesis is used to convert spatial rainfall intensity fluctuations to temporal fluctuations at a given location A. The combined physical-statistical model gives the distribution of the maximum rainfall intensity at A during a period of duration D for a TC with characteristics (Vmax, Rmax, Vt) that passes at a given distance from A. To illustrate the use of the model for long-term rainfall risk analysis, we formulate a recurrence model for tropical cyclones in the Gulf of Mexico that make landfall between longitudes 85°-95°W. We then use the rainfall and recurrence models to assess the rainfall risk for New Orleans. For return periods of 100 years or more and long averaging durations (D around 12-24 hours), tropical cyclones dominate over other rainfall event types, whereas the reverse is true for shorter return periods or shorter averaging durations.
by Andreas Langousis.
Ph.D.
6
Guthrie, James Harold. "Extreme rainfall in the greater Calgary area." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ64957.pdf.
Повний текст джерела
7
Zhou, Chen. "On extreme value statistics maximum likelihood portfolio optimation extremal rainfall Internet auctions /." [Amsterdam] : Rotterdam : Thela Thesis ; Erasmus University [Host], 2008. http://hdl.handle.net/1765/14290.
Повний текст джерела
8
Keef, Caroline. "Spatial dependence of river flooding and extreme rainfall." Thesis, Lancaster University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485231.
Повний текст джерелаАнотація:
The extent of spatial dependence of flooding and extreme rainfall in Britain is unknown. In this thesis we develop existing extreme value theory to study this phenomenon. It is important to know the level of spatial dependence of flooding because if a flood occurs at multiple sites at the same time the consequences for (for example) the emergency services and the insurance industry can be more severe than if these floods occurred at different times. There are various features of river flow and rainfall data that complicate the estimation of extremal dependence. The two main features are the presence of missing data and the temporal dependence of the individual time series. Heffernan and Tawn (2004) developed a flexible method for modelling multivariate extreme values that can be used for a large number of variables. In this thesis we develop and extend this method to handle the presence of missing data and temporal dependence. We apply this extended method separately to river flow and rainfall data to estimate the level of spatial dependence of flooding and extreme rainfall over Britain. We find that heterogeneous regions in terms of the geology and soil types show low levels of spatial dependence. As we would expect we also find that connected rivers show a high level of dependence between them. We also find that the upland regions of Britain have low levels of spatial dependence of extreme rainfall.
9
Atyeo, Jonathan. "Models for trends and dependence in extreme rainfall." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440569.
Повний текст джерела
10
De, Waal Jan Hofmeyr. "Extreme rainfall distributions : analysing change in the Western Cape." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71654.
Повний текст джерелаАнотація:
Thesis (MSc)--Stellenbosch University, 2012.Severe floods in the Western Cape have caused significant damage to hydraulic structures, roads and other infrastructure over the past decade. The current design criteria for these structures and flood return level calculations are based on the concept of stationarity, which assumes that natural systems vary within an envelope of variability that does not change with time. In the context of regional climate change and projected changes in rainfall intensity, the basis for these calculations may become unrealistic with the passage of time. Hydraulic structures and other infrastructure may become more vulnerable to damaging floods because of changing hydroclimatic conditions. This project assesses the changes in extreme rainfall values over time across the Western Cape, South Africa. Using a Generalised Pareto Distribution, this study examines the changes in return levels across the Western Cape region for the periods 1900-1954 and 1955-2010. Of the 137 rainfall stations used in this research, 85 (62%) showed an increase in 50-year return level, 30 (22%) a decrease in 50-year return level and 22 (16%) stations displayed little change in rainfall intensity over time. While there were no clear spatial patterns to the results, they clearly indicate an increase in frequency of intense rainfalls in the latter half of the 20th and early 21st century. The changes in return level are also accompanied by a change in the frequency of high intensity 2-3 day long storms. 115 (84%) of the 137 rainfall stations showed an increase in the frequency of long duration, high intensity storms over the data record. This change generates a shifting risk profile of extreme rainfalls, which, in turn, creates challenges for the design of hydraulic structures and any infrastructure exposed to the resulting damaging floods. It can therefore be argued that it is inappropriate to design structures or manage water resources assuming stationarity of climate and that these principles should be assessed in order to reduce the risk of flood damage owing to increasing storm intensity. KEY WORDS Flood Risk, Stationarity, Disaster Risk, Hazard, Extreme Rainfall, Generalized Pareto Distribution, Climate
11
Morison, David. "The synoptic drivers of extreme rainfall in South Africa." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/6610.
Повний текст джерелаАнотація:
A number of studies have shown an increase in the intensity of extreme rainfall over many regions of South Africa during the last 50 to 100 years. However, the weather of a region at any given time is a direct function of the synoptic state of the atmosphere at that particular time. This thesis identifies synoptic states associated with extreme rainfall at a regional scale over South Africa and also investigates trends in extreme rainfall characteristics. Using 31 years of rainfall station data across South Africa, days which experienced extreme rainfall events, defined as the 95th and 99th percentile, were identified. These were then matched against mean sea-level pressure and 500hPa geopotential height circulation patterns obtained from the Climate Forecast System Reanalysis (CFSR) dataset to investigate the driving synoptics of extreme rainfall. Self-organizing maps (SOMs) were used to characterize the synoptic circulations on a general country-wide scale as well as for 8 different regional rainfall regimes at a seasonal scale. Synoptic circulations associated with extreme rainfall events often involved an interaction between more than one synoptic feature such as a linkage between a sub-tropical low pressure system and a mid-latitude cyclone or a ridging high pressure and a continental low pressure. Some features known for contributing towards a significant amount of extreme rainfall events such as cut-off lows in the south-western parts of the country were poorly characterized by the regional SOMs. This may be attributed to the spatial boundaries adopted in this study and suggests general rainfall regimes developed for South Africa are not appropriate for extreme rainfall analyses. Trends in extreme rainfall were assessed in the observed station data with the RClimDex software package and used ten extreme rainfall indices. Apart from the Simple Daily Intensity Index (SDII), which identified a number of significantly increasing trends amongst various stations throughout the country, very few significant trends were identified in the remaining indices. This may be attributed to the infrequent nature of extreme rainfall events and the relatively short 31 year study period. It was, however, discovered that 4 stations with significantly increasing trends in extreme rainfall were paired with synoptic circulations associated with extreme rainfall in the summer rainfall regime that had also experienced significantly increasing trends. Thus the characteristics of extreme rainfall identified in the station data have been associated with the driving synoptic scale circulations and their changing characteristics. However, the generalized regional rainfall regimes identified across South Africa are not appropriate for the study of extreme rainfall synoptic drivers. Here an event-based analysis would provide better insight to the attributes of specific extreme rainfall driving synoptics as well as providing an improved assessment of regional extreme rainfall.
12
Mondonedo, Carlo Arturo S. J. "Enhanced Extreme Rainfall Generation in Temporal Point Process Modeling." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124492.
Повний текст джерела
13
Boers, Niklas. "Complex network analysis of extreme rainfall in South America." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17237.
Повний текст джерелаАнотація:
Basierend auf der Theorie von Netzwerken wird ein allgemeines Rahmenwerk entwickelt, um kollektive Synchronisationsphänome von Extremereignissen in komplexen Systemen zu studieren. Die Methode vergleicht die Variabilität der einzelnen Teile des Systems auf Grundlage von Beobachtungszeitreihen mit dem Ziel, emergente Synchronisationsmuster von Extremereignissen auf makroskopischer Ebene aufzudecken. Zu diesem Zweck werden die einzelnen Zeitreihen eines interaktiven Systems mit den Knoten eines Netzwerks identifiziert und die Abhängigkeiten zwischen diesen durch die Kanten des Netzwerks dargestellt. Die komplexe interne Synchronisationsstruktur des Systems wird so in Form der Netzwerktopologie mathematisch zugänglich gemacht und kann durch die Einführung geeigneter Netzwerkmaße analysiert werden. Die Methode wird im Folgenden auf räumlich und zeitlich hochaufgelöste Regendaten aus Satellitenmessungen angewendet, um die kollektive Dynamik extremer Regenereignisse in Südamerika zu untersuchen. Diese Anwendung verfolgt drei Ziele: Erstens wird gezeigt, wie die hier entwickelte Methode zur klimatologischen Analyse verwendet werden kann. Zweitens können Quellen und Senken von Extremereignissen durch die Einführung des Konzeptes der Netzwerkdivergenz identifiziert werden. Dies erlaubt es, die gerichteten Netzwerkpfade, entlang derer Extremereignisse synchronisieren, nachzuverfolgen. Auf dieser Grundlage wird eine statistische Regel gewonnen, die beträchtliche Anteile der extremen Regenereignisse in den Zentralanden vorhersagt. Drittens werden die bis dahin entwickelten Methoden und gewonnenen Einsichten dazu verwendet, die Darstellung extre- mer Regenereignisse in verschiedenen Datensätzen zu vergleichen. Insbesondere wird in diesem Kontext die Implementierung solcher Ereignisse in drei gängigen Klimamodellen evaluiert.Based on the theory of networks, a general framework is developed to study collective synchronization phenomena of extreme events in complex systems. The method relies on observational time series encoding the variability of the single parts of the system, and is intended to reveal emerging patterns of extreme event synchronization on the macroscopic level. For this purpose, the time series obtained from an interactive system under consideration are identified with network nodes, and the possibly delayed and non-linear interdependence of extreme events in different time series is represented by network links connecting the nodes. In this way, the complex internal synchronization structure of the system becomes accessible in terms of the topology of the network, which can be analyzed by introducing suitable network measures. The methodology is applied to satellite-derived rainfall time series of high spatiotemporal resolution in order to investigate the collective dynamics of extreme rainfall events in South America. The purpose of this application is threefold: First, it is shown how the methodology can be used for climatic analysis by revealing climatological mechanism from the spatial patterns exhibited by different network measures. Second, by introducing the concept of network divergence, sink and source regions of extreme events can be identified, allowing to track their directed synchronization pathways through the network. A simple statistical forecast rule is derived on this basis, predicting substantial fractions of extreme rainfall events in the Central Andes. Third, the methodology and the insights developed in the first two steps are used to evaluate the dynamical representation of extreme events in different datasets, and in particular their dynamical implementation in three state of the art climate models.
14
Jobin, Erik. "An Urban Rainfall Storm Flood Severity Index." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24124.
Повний текст джерелаАнотація:
Extreme rainfall statistics are important for the design and management of the water resource infrastructure. The standard approach for extreme rainfall event severity assessment is the Intensity-Duration-Frequency (IDF) method. However, this approach does not consider the spatial context of rainfall and consequently does not properly describe rainfall storm severity, nor rarity. This study provides a critical account of the current standard practice and presents an approach that takes into consideration both the spatial context of rainfall storms, and indirectly incorporates runoff to produce a representative approach to assessing urban rainfall storm severity in terms of flood potential. A stepwise regression analysis was performed on a dataset of individual rainfall storm characteristics to best represent documented basement floodings in the City of Edmonton. Finally, the urban rainfall storm flood severity index was shown to be most representative of the documented basement floodings' severity when compared to that of the IDF method.
15
Cung, Annie. "Statistical modeling of extreme rainfall processes in consideration of climate change." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100788.
Повний текст джерелаАнотація:
Extreme rainfall events may have catastrophic impacts on the population and infrastructures, therefore it is essential to have accurate knowledge of extreme rainfall characteristics. Moreover, both the scientific community and policymakers have recently shown a growing interest in the potential impacts of climate change on water resources management. Indeed, changes in the intensity and frequency of occurrence of extreme rainfall events may have serious impacts. As such, it is important to understand not only the current patterns of extreme rainfalls but also how they are likely to change in the future.The objective of the present research is therefore to find the best method for estimating accurately extreme rainfalls for the current time period and future periods in the context of climate change. The analysis of extreme rainfall data from the province of Quebec (Canada) revealed that, according to L-moment ratio diagrams, the data may be well described by the Generalized-Extreme-Value (GEV) distribution. Results also showed that a simple scaling relationship between non-central moments (NCM) and duration can be established and that a scaling method based on NCMs and scaling exponents can be used to generate accurate estimates of extreme rainfalls at Dorval station (Quebec, Canada). Other results demonstrated that the method of NCMs can accurately estimate distribution parameters and can be used to construct accurate Intensity-Duration-Frequency (IDF) curves.
Furthermore, a regional analysis was performed and homogenous regions of weather stations within Quebec were identified. A method for the estimation of missing data at ungauged sites based on regional NCMs was found to yield good estimates.
In addition, the potential impacts of climate change on extreme rainfalls were assessed. Changes in the distribution of annual maximum (AM) precipitations were evaluated using simulations from two Global Climate Models (GCMs) under the A2 greenhouse gas emission scenario: the Coupled Global Climate Model version 2 (CGCM2A2) of the Canadian Centre for Climate Modelling and Analysis, and the Hadley Centre's Model version 3 (HadCM3A2). Simulations from these two models were downscaled spatially using the Statistical DownScaling Model (SDSM). A bias-correction method to adjust the downscaled AM daily precipitations for Dorval station was tested and results showed that after adjustments, the values fit the observed AM daily precipitations well. The analysis of future AM precipitations revealed that, after adjustments, AM precipitations downscaled from CGCM2A2 increase from current to future periods, while AM precipitations downscaled from HadCM3A2 show a mild decrease from current to future periods, for daily and sub-daily scales.
16
Collier, Andrew Jason. "Extreme value analysis of non-stationary processes : a study of extreme rainfall under changing climate." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1219.
Повний текст джерелаАнотація:
The aim of this study has been to gain a greater understanding of the accuracy and levels of uncertainty associated with extreme rainfall event estimates, whilst considering both stationary and non-stationary processes (climate change). This study started with the analysis and comparison of two extreme event fitting/estimation techniques: Linear Moments (L-Moments) and Maximum Likelihood Estimation (MLE) for the estimation of Generalized Extreme Value (GEV) distribution parameters. This thesis has found that MLE provides a number of advantages over L-Moments, especially when working with long or pooled data sets. These advantages include: The generation of confidence limits; Homogeneity testing; and, Trend detection / simulation. However, the results of the analysis show that it is advisable to use L-Moments for single site analysis when the available data is less than 40 years in length. In this situation, L-Moments were found to produce less uncertainty. Hosking and Wallis (1988) defined a method for the generation of synthetic data sets; this work has been reproduced and built upon as part of this thesis. Using this method it has been possible to gain insight on: Inter-site-dependence versus spatial separation (distance, km); The effects of inter-site-dependence on pooling groups; Regional correlation descriptors (level of dependence in a region); Synthetic data generation for regions with varying levels of dependence; Network Maximum (Netmax) Growth Curves; and, The effective number of sites in a defined region/pooling group. This has been carried out using the „R‟ statistical software/programming environment. Dales and Reed (1989), proposed the use of Netmax data (the largest value for one year across the network or pooling group) to increase the accuracy at the tail of an extreme event distribution by theoretically extending the curve. This hypothesis suggests that the separation between these two curves (the regional growth curve and the Netmax growth curve) is constant; allowing the Netmax curve to be translated and overlain on the regional growth curve. This study has found that the separation varies iv with return period, implying that spatial correlation reduces (events become more independent) with increased rarity (or return period). However, these findings suggest complications with the use of Netmax data for the purpose of extending the regional growth curve. In addition to the work detailed above, a method of trend detection in annual maximum rainfall has been demonstrated using synthetic data. Synthetic data has been used to enable control over the data, with this greater certainty and understanding in the results are achieved. The same analysis was repeated on observed annual maxima for 1, 5 and 10 day durations, revealing evidence of trends, with stronger signals at higher durations. The trend was detected in the Location parameter, which relates to the mean. When using Synthetic data to understand the sensitivity of this test, it was found that the Location parameter required the weakest trend to be detected. In summary this thesis has used synthetic data to gain a better understanding of: 1. Distribution fitting techniques; 2. Single site analysis; 3. Regional Analysis; 4. Spatial dependence; and, 5. Trend Detection. All of the software that has been written as a result of this thesis to demonstrate the topics discussed, is included in Appendix 5, with explanations on the method of use. Should additional information be required, please contact Professor C. Kilsby at Newcastle University, who will forward on your enquiry.
17
Miniussi, Arianna. "The metastatistical extreme value distribution for rainfall and flood frequency analysis with external drivers." Doctoral thesis, Università degli studi di Padova, 2021. http://hdl.handle.net/11577/3425928.
Повний текст джерелаАнотація:
An accurate estimation of hydrologic extremes is fundamental for its manyimplications on engineering design, flood quantification and mapping, insurance and re-insurance purposes, policy-making. Traditional methods,hinging on the Generalized Extreme Value (GEV) distribution, are founded on often-overlooked and untested assumptions, make an ineffective use of
the available data, and are ill-suited for accounting for inter-annual variability. With the aim of improving the estimation accuracy of high return period extremes, this dissertation focuses on the Metastatistical Extreme Value Distribution (MEVD), an approach introduced to relax some of the limitations of the traditional Extreme Value Theory. The present work first
analyzes the definition of the optimal MEVD formulation as a function of local climatic factors and of key statistical properties of rainfall at the daily scale. It concludes that the inter-annual variability of rainfall statistical properties plays an important role in the definition of the optimal time window to be used for parameter estimation. In the largest amount of cases examined, except for very dry climates, with few rainy days, the analysis window should be kept to the minimum of 1 year in order to resolve the time variability of the distributions. The use of short time windows also makes the MEVD a suitable approach to study extremes in a changing climate, as it contributes to its ability to resolve inter-annual variability. Up to now, the MEVD has been applied mainly to rainfall (at the daily and hourly scale). Here, for the first time, the MEVD is used to study streamflow data, developing a flood frequency analysis MEVD-based on series of flow peaks in the Continental United States. Moreover, the impact of El Niño Southern Oscillation (ENSO) on flood regimes is evaluated. In the
comparison with the GEV, results show the outperformance of the MEVD in ~76% of the analyzed stations, with a significant reduction in the estimation error especially when considering return periods much higher than the size of the sample used to estimate the distributional parameters. Yet, a negligible improvement in the estimation of extreme floods was found when stratifying peaks according to ENSO phases. In the end, leveraging the appealing property of the MEVD to naturally include mixtures of distributions in its formulation, a MEVD that distinguishes between non-Tropical Cyclones (TCs) and Tropical Cyclones-induced rainfall is applied to several American metropolitan areas. The impact of TCs on rainfall is well distinguishable, and the use of a mixed MEVD approach resulted beneficial in several cases. Its advantage in the reduction of the estimation error when compared to the single-distribution MEVD was found to be more significant when considering cumulative values of rainfall over consecutive days, due to the prolonged impact TCs have on rainfall over time.
18
Bougadis, John. "Detection of trends in extreme rainfall in the province of Ontario." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26452.
Повний текст джерелаАнотація:
Information on intensity-duration-frequency (IDF) of rainfall is commonly required for the design, construction, and management of many water resources projects involving natural hazards, due to extreme rainfall events. Design storms (DS) are determined from IDF relationships. Many hydraulic structures (dams, weirs, culverts, storm sewer systems, etc.) are designed to serve 50 years or more into the future. Yet, these structures are being sized for the climatic conditions based on the past records, before climate change. Thus, new design methods accounting for climatic change are needed to prevent potential losses and damages resulting from under-design. This research addresses the issue of the effect of climate change on design storms. The major objectives of this study are to detect trends in extreme rainfall, and to estimate anticipated changes in return periods of extreme rainfall events due to trends.
In this study, trends (which might be attributed to climate change) are estimated for different durations of annual extreme rainfall using the regional average Mann-Kendall's S trend test. Numerical analysis was performed on 44 rainfall stations from the province of Ontario, Canada for a 20 and 25 year time frame. (Abstract shortened by UMI.)
19
Singleton, Andrew Thomas. "Cut-off low pressure systems and extreme rainfall over South Africa." Doctoral thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6504.
Повний текст джерелаАнотація:
Includes bibliographical references (p. 257-271).This thesis is an investigation of cut-off low pressure systems over South Africa. These weather systems have been responsible for many of the flooding disasters that have affected South Africa, particularly the coastal regions, over recent decades. The thesis has two main objectives, namely, to construct a 30-year climatology of cut-off lows over South Africa, and to further understanding of the evolution of the low-level flow that leads to these systems producing extreme quantities of rainfall.
20
Nassor, Abdallah. "Monsoon surges, tropical cyclones and extreme rainfall events in NW Madagascar." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/21516.
Повний текст джерелаАнотація:
Rainfall variability in NW Madagascar and the kinematics and thermodynamics of flood-producing weather systems affecting the region are examined. Daily rainfall in the austral summer are used to select 16 cases for the composite analysis of flood events in the period 1987-1992. In addition two cases of flood events are studied individually. The first flood event occurred in 1991 and brought420 mm of rainfall in 24 hours at Maintirano during the passage of tropical cyclone (TC) Cynthia, an eastward moving TC from the Mozambique Channel. The second flood event occurred in 1992and brought 347 mm of rainfall in 24 hours at Mahajanga due to the passage of TC Bryna, a westward moving TC from the Indian Ocean. Inter-annual rainfall variability is correlated with the indices: TC day frequency, QBO and SOI, and a useful value is found with the first index but not with the two latter global indices. An intraseasonal analysis indicates that wet spells have a duration of 15 to 20 days. Daily spectra analysisof rainfall reveals the complexity of interplay between the convective forcing features. Cycles of 10-20 days are contributed by easterly waves, while 40 day cycles are produced by monsoon surges. The composite analysis identifies the following features: an eastward shift of active convection from Mozambique across Madagascar in conjunction with a surge of the NW monsoon and weakening of the easterlies in the lower troposphere. These factors promote TC genesis. Other supporting influences include the development of an anticyclonic circulation in the upper level over the island with north westward outflow. This often coincides with an east phase QBO, an upper level eastward moving mid-latitude trough and a persistent moisture flux convergence over the island throughout TC passage. The topography of Madagascar plays an important role in the intensification of the flood producing weather system by enhancing the cloud vortex in the NW region of the island.
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Dok, Atitkagna. "Tertiary Creep Behavior of Landslides Induced by Extreme Rainfall: Mechanism and Application." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175207.
Повний текст джерела
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Lee, Min Young. "Statistical modeling of extreme rainfall processes in the context of climate change." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114421.
Повний текст джерелаАнотація:
The occurrence of extreme storms is a critical consideration in the design and management of a large number of water-resource projects. In current engineering practice, the estimation of extreme rainfalls is accomplished based on statistical frequency analysis of maximum precipitation data. The objective of this frequency analysis is hence to estimate the maximum amount of precipitation falling at a given point for a specified duration and return period. Results of precipitation frequency analysis are often summarized by "intensity-duration-frequency" (IDF) relationships for a given site. However, traditional methods in the development of IDF relations have two major limitations. Firstly, these existing methods were not able to account for the extreme rainfall characteristics over different time scales. Secondly, these traditional methods cannot take into account the potential impacts of climate variability and climate change. Therefore, the main objective of the present study is to propose an improved method for extreme rainfall estimation that could overcome these limitations. The proposed method was based on the scale-invariance GEV distribution and the statistical downscaling procedure to construct the IDF relations in the context of climate change. The Non-Central Moment method was used for the estimation of the three parameters of the GEV. Results of a numerical application using Annual Maximum Precipitation (AMP) data from a network of 14 rain-gauge stations in South Korea has indicated the feasibility and accuracy of the suggested method. In particular, the observed AMP series displayed a simple scaling behaviour. In addition, the linkages between global climate variables given by two Global Climate Models (GCMs) (one from Environment Canada and one from the UK Hadley Centre) and the local extreme rainfall characteristics have been successfully established for predicting the resulting changes of the IDF relations under different climate change scenarios A2, A1B, and B2. It was found that the IDF relations for future periods (2020's, 2050's, and 2080's) showed increasing or decreasing trends depending on the GCM used and the climate scenario considered.La fréquence des tempêtes extrêmes est un facteur critique dans la conception et gestion d'un grand nombre de projets de ressources en eau. Dans la pratique courante, l'estimation des pluies extrêmes est réalisée en se basant sur l'analyse de fréquence statistique des données de précipitations maximales. L'objectif de cette analyse de la fréquence est donc d'estimer le montant maximal de précipitations qui tombent à un moment donné pendant une durée déterminée, ainsi que la période de retour. Les résultats de l'analyse de la fréquence des précipitations sont souvent résumés par les relations Intensité-Durée-Fréquence (IDF) pour un site donné. Toutefois, les méthodes traditionnelles dans le développement des relations IDF ont deux limites majeures. Tout d'abord, ces méthodes n'ont pas été en mesure de tenir compte des caratéristiques des précipitations extrêmes sur des différentes échelles de temps. Deuxièmement, ces méthodes traditionnelles ne tiennent pas compte des impacts potentiels de la variabilité climatique et du changement climatique. Par conséquent, l'objectif principal de cette présente étude est de proposer une méthode d'estimation des précipitations extrêmes améliorée qui pourrait surmonter ces limitations. La méthode proposée a été basée sur l'échelle d'invariance de distribution GEV et la procédure de réduction d'échelle statistique pour construire des relations IDF dans le contexte du changement climatique. La méthode des moments non-centraux a été utilisée pour l'estimation des trois paramètres de la GEV. Les résultats obtenus par une application numérique des données de Précipitations Maximales Annuelles (PMA) à partir d'un réseau de 14 stations pluviométriques en Corée de Sud ont démontré la faisabilité et la précision de la méthode proposée. La série de PMA observée a particulièrement affiché une propriété d'échelle simple. En outre, les liens entre les variables climatiques globaux donnés par les deux Modèles Climatiques Globaux (MCGs) (un en provenance d'Environnement Canada et l'autre du Centre Hadley du Royaume-Uni) et les caractéristiques des précipitations locaux extrêmes ont été établis avec succès pour prédire les changements qui résultent des relations IDF selon des différents scénarios climatiques - A2, A1B, et B2. Il a été constaté que des relations IDF pour les périodes futures (les années 2020, 2050, et 2080) ont démontré des tendances qui augmentent ou diminuent dépendemment des MCG utilisés et du scénario climatique à l'étude.
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Bhatti, Babar Mahmood 1968. "Extreme rainfall, flood scaling and flood policy options in the United States." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9092.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2000.Includes bibliographical references (leaves 220-227).
River flood and rainfall have been shown to exhibit scale invariance behavior over a range of space and time scales. Although various approaches have been taken to investigate and model the various scaling aspects of rainfall and floods, little theoretical work has been done on the relation between the scaling of rainfall and flood. If available, such a theory would provide frequency estimate for extreme rainfall and floods outside the range of observations and could also be used to estimate floods at ungaged basins. The relationship between rainfall and flood scaling is the main focus of this thesis. We use a two step approach to investigate the relationship between exponent of peak flows and the scaling of rain. First, we use data analysis to verify existing theories that relate the multi scaling behavior of rainfall to the simple scaling behavior of the IDFs. Second, we use a model to relate the scaling of the IDFs to the scaling of peak flows with basin area. We find that, although temporal rainfall shows multiscaling, the IDFs exhibit simple scaling and peak floods show simple or mild multiscaling. We validate our findings by using U.S. peak annual flow data and rainfall from a few New England stations. Extreme floods damage mitigation requires sound and integrated policy making. We review the flood disaster mitigation situation in the U.S., carry out policy analysis and recommend options for a successful and sustainable flood disaster policy in the U.S.
by Babar Mahmood Bhatti.
S.M.
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Abba, Omar Sabina. "Capability of CORDEX RCMs in simulating extreme rainfall events over South africa." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9103.
Повний текст джерелаАнотація:
Includes bibliographical references.In South Africa, extreme rainfall events often lead to widespread destruction, damage infrastructure, displace communities, strain water management and even destroy lives. Past studies have shown that reliable predictions of extreme rainfall events from regional climate models (RCMs) could help reduce the impact of these events. The present study evaluates the ability of nine RCMs in simulating extreme rainfall events over South Africa, focusing on the Western Cape (WC) and east coast (EC) areas. This study defines an extreme rainfall over a location as rainfall that is equal to or above the 95th percentile of the rainfall distribution at that location, and defines widespread extreme rainfall events (WEREs) over an area as events during which more than 50 of the grid-points in the area experience extreme rainfall. The 95th percentile threshold values were calculated over 11 years (1998-2008) of South Africa’s daily rainfall data from the nine RCMs (CCLM, REMO, PRECIS, CRCM5, ARPEGE, REGCM3, WRF, RACMO and RCA35), which participated in the Coordinated Regional Climate Downscaling Experiment (CORDEX) and used ERA-Interim (ERAINT) as their boundary forcing. The simulations were compared to two observation datasets (TRMM and GPCP), and to ERAINT rainfall data to understand whether these RCMs improve on the results from ERAINT. A self organizing map (SOM) was used to characterize WEREs identified in all the datasets into archetypal groups, and ERAINT data is used to describe the underlying circulations for each archetypal rainfall pattern. The number of WEREs mapped to each rainfall pattern for each dataset allows us to get an idea of whether certain RCMs are more likely to simulate certain rainfall patterns.
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Pinto, Izidine S. de Sousa. "Future changes in extreme rainfall events and circulation patterns over southern Africa." Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16781.
Повний текст джерелаАнотація:
Includes bibliographical referencesChanges in precipitation extremes are projected by many global climate models as a response to greenhouse gas increases, and such changes will have significant environmental and social impacts. These impacts are a function of exposure and vulnerability. Hence there is critical need to understand the nature of weather and climate extremes. Results from an ensemble of regional climate models from the Coordinated Regional Downscaling Experiment (CORDEX) project are used to investigate projected changes in extreme precipitation characteristics over southern Africa for the middle (2036-2065) and late century (2069-2098) under the representative concentration pathway 4.5 (RCP4.5) and 8.5 (RCP8.5). Two approaches are followed to identify and analyze extreme precipitation events. First, indices for extreme events, which capture moderate extreme events, are calculated on the basis of model data and are compared with indices from two observational gridded datasets at annual basis. The second approach is based on extreme value theory. Here, the Generalized Extreme Value distribution (GEV) is fitted to annual maxima precipitation by a L-moments method. The 20-year return values are analyzed for present and future climate conditions. The physical drivers of the projected change are evaluated by examining the models ability to simulate circulation patterns over the regions with the aid of Self-Organizing Maps (SOM).
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Ávila, Díaz Álvaro Javier. "Extreme rainfall indices in Brazilian mountain regions and potentially induced hydrological hazards." Universidade Federal de Viçosa, 2016. http://www.locus.ufv.br/handle/123456789/7806.
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Fundação de Amparo à Pesquisa do Estado de Minas Gerais
O recente aumento do número de inundações e movimentos de massa na região densamente povoada no sudeste do Brasil, o presente estudo analisa as alterações espaciais e temporais na precipitação durante o período de 1978-2014, nas regiões montanhosas dos estados brasileiros do Rio de Janeiro e Santa Catarina. Avaliou-se a presença de tendência nas series sazonais, anuais e do conjunto de índices extremos de precipitação onde foi usado o software Rclimdex. As series são calculados a partir das series precipitação diária. Com base nos resultados observou-se que nas escalas anuais e sazonais se tem um aumento de precipitação, exceto para a temporada de inverno na região montanhosa de Rio de Janeiro. Além disso, foram encontradas de mudanças abrutas em diferentes anos para as séries de tempo analisadas, diferenças espaciais nas tendências em estações individuais e tendências associadas com elevação sugerem que apesar da proximidade destas duas regiões, os impactos do clima não são uniformes em todo o sudeste do Brasil. Os mecanismos de clima responsáveis pelas tendências de precipitação observada são identificados, mas trabalho adicional é necessário para isolar as causas. Por outro lado, o número de desastres naturais de tipo hidrológico como os movimentos de massa/enchentes estão aumentando. Este tipo desastre mostrou correlações positivas significativas com os índices 1-day (máximo de precipitação anual em um dia) e o 5-dias (máximo de precipitação anual em cinco dias consecutivos), sendo assim índices que podem ser úteis indicadores de eventos de risco hidrológicos para estas regiões.
In order to understand the rising number of flash floods and mass movements in the densely populated region of southeastern Brazil, this study analyzes the spatial and temporal changes in precipitation from 1978 to 2014. We focus on the sensitivity of mountainous regions, specifically the Rio de Janeiro (RJMR) and Santa Catarina (SCMR) regions. Daily rainfall observations are aggregated into annual and seasonal indices, and RClimdex is used to evaluate a suite of precipitation and extreme event indices. Results show positive annual and seasonal precipitation trends during all seasons except for the winter season in the RJMR. Diverse change points in their time series, spatial differences in the trends at individual stations, and trends associated with elevation suggest that despite the close proximity of these two regions, climate impacts are not uniform across all of southeastern Brazil. Climate mechanisms responsible for the observed precipitation trends are identified, but additional work is needed to isolate the causes. Statistically significant positive correlations are discovered between mass movements/flash floods events and annual maximum 1–day and 5–day consecutive precipitation, and these indices may be useful indicators of natural hazard events for this region.
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Tanaka, Tomohiro. "Extreme flood frequency analysis and flood risk curve development considering spatiotemporal rainfall variability." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217150.
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Eljabri, Sumaya Saleh M. "New statistical models for extreme values." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/new-statistical-models-for-extreme-values(12e1ec08-dc66-4f20-a7dc-c89be62421a0).html.
Повний текст джерелаАнотація:
Extreme value theory (EVT) has wide applicability in several areas like hydrology, engineering, science and finance. Across the world, we can see the disruptive effects of flooding, due to heavy rains or storms. Many countries in the world are suffering from natural disasters like heavy rains, storms, floods, and also higher temperatures leading to desertification. One of the best known extraordinary natural disasters is the 1931 Huang He flood, which led to around 4 millions deaths in China; these were a series of floods between Jul and Nov in 1931 in the Huang He river.Several publications are focused on how to find the best model for these events, and to predict the behaviour of these events. Normal, log-normal, Gumbel, Weibull, Pearson type, 4-parameter Kappa, Wakeby and GEV distributions are presented as statistical models for extreme events. However, GEV and GP distributions seem to be the most widely used models for extreme events. In spite of that, these models have been misused as models for extreme values in many areas.The aim of this dissertation is to create new modifications of univariate extreme value models.The modifications developed in this dissertation are divided into two parts: in the first part, we make generalisations of GEV and GP, referred to as the Kumaraswamy GEV and Kumaraswamy GP distributions. The major benefit of these models is their ability to fit the skewed data better than other models. The other idea in this study comes from Chen, which is presented in Proceedings of the International Conference on Computational Intelligence and Software Engineering, pp. 1-4. However, the cumulative and probability density functions for this distribution do not appear to be valid functions. The correction of this model is presented in chapter 6.The major problem in extreme event models is the ability of the model to fit tails of data. In chapter 7, the idea of the Chen model with the correction is combined with the GEV distribution to introduce a new model for extreme values referred to as new extreme value (NEV) distribution. It seems to be more flexible than the GEV distribution.
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Eckersten, Sofia. "Updating Rainfall Intensity-Duration-Frequency Curves in Sweden Accounting for the Observed Increase in Rainfall Extremes." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-283714.
Повний текст джерелаАнотація:
Increased extreme precipitation has been documented in many regions around the world, in- cluding central and northern Europe. Global warming increases average temperature, which in turn enhances atmospheric water holding capacity. These changes are believed to increase the frequency and/or intensity of extreme precipitation events. In determining the design storm, or a worst probable storm, for infrastructure design and failure risk assessment, experts commonly assume that statistics of extreme precipitation do not change significantly over time. This so- called notion of stationarity assumes that the statistics of future extreme precipitation events will be similar to those of historical observations. This study investigates the consequences of using a stationary assumption as well as the alternative: a non-stationary framework that con- siders temporal changes in statistics of extremes. Here we evaluate stationary and non-stationary return levels for 10-year to 50-year extreme precipitation events for different durations (1-day, 2-day, ..., 7-day precipitation events), based on the observed daily precipitation from Sweden. Non-stationary frequency analysis is only considered for stations with statistically significant trends over the past 50 years at 95% confidence (i.e., 15 to 39 % out of 139 stations, depend- ing on duration, 1-day, 2-day, ..., 7-day). We estimate non-stationary return levels using the General Extreme Value distribution with time-dependent parameters, inferred using a Bayesian approach. The estimated return levels are then compared in terms of duration, recurrence in- terval and location. The results indicate that a stationary assumption might, when a significant trend exists, underestimate extreme precipitation return levels by up to 40 % in Sweden. This report highlights the importance of considering better methods for estimating the recurrence in- terval of extreme events in a changing climate. This is particularly important for infrastructure design and risk reduction.Ökad extrem nederbörd har dokumenterats globalt, däribland centrala och norra Europa. Den globala uppvärmningen medför en förhöjd medeltemperatur vilket i sin tur ökar avdunstning av vatten från ytor samt atmosfärens förmåga att hålla vatten. Dessa förändringar tros kunna öka och intensifiera nederbörd. Vid bestämning av dimensionerande nederbördsintensiteter för byggnationsprojekt antas idag att frekvensen och storleken av extrem nederbörd inte kommer att förändras i framtiden (stationäritet), vilket i praktiken innebär ingen förändring i klimatet. Den här studien syftar till att undersöka effekten av en icke-stationärt antagande vid skattning av dimensionerande nederbördsintensitet. Icke-stationära och stationära nerderbördsintensiteter föråterkomsttider mellan 10 och 100år bestämdes utifrån daglig och flerdaglig svensk nederbörds- data. Nederbördintensiteterna bestämdes med extremvärdesanalys i mjukvaran NEVA, där den generella extremvärdesfördelningen anpassades till årlig maximum nederbörd på platser i Sverige som påvisade en ökande trend under de senaste 50åren (15% till 39 % utav 139 stationer, beroende på varaktighet). De dimensionerande nederbördsintensiteterna jämfördes sedan med avseende på varaktighet, återkomsttid och plats. Resultaten indikerade på att ett stationärt antagande riskerar att underskatta dimensionerande nederbördsintensiteter för en viss återkomsttid med upp till 40 %. Detta indikerar att antagandet om icke-stationäritet har större betydelse för olika platser i Sverige, vilket skulle kunna ge viktig information vid bestämning av dimensionerande regnintensiteter.
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Mahjabin, Tasnuva. "Long-term Trends in Magnitude and Frequency of Extreme Rainfall Events in Florida." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2257.
Повний текст джерелаАнотація:
This study computed trends in extreme precipitation events of Florida for 1950-2010. Hourly aggregated rainfall data from 24 stations of the National Climatic Data Centre were analyzed to derive time-series of extreme rainfalls for 12 durations, ranging from 1 hour to 7 day. Non-parametric Mann-Kendall test and Theil-Sen Approach were applied to detect the significance of trends in annual maximum rainfalls, number of above threshold events and average magnitude of above threshold events for four common analysis periods. Trend Free Pre-Whitening (TFPW) approach was applied to remove the serial correlations and bootstrap resampling approach was used to detect the field significance of trends. The results for annual maximum rainfall revealed dominant increasing trends at the statistical significance level of 0.10, especially for hourly events in longer period and daily events in recent period. The number of above threshold events exhibited strong decreasing trends for hourly durations in all time periods.
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Haylock, Malcolm. "Interannual variability of mean and extreme rainfall and relationship with large-scale circulation." Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427078.
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Egbebiyi, Temitope Samuel. "Future changes in extreme rainfall events and African easterly waves over West Africa." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20581.
Повний текст джерелаАнотація:
This study examines the relationship between African Easterly Waves (AEWs) and extreme rainfall events over West Africa, and investigates how climate change could alter this relationship in the future. Satellite observations, reanalysis data, and regional climate model (RCA4) simulations (forced with eight global climate simulations) were analysed for the study. The study used the 95th percentile of daily rainfall as a threshold to identify extreme rainfall events, and applied spectral analysis to extract 3-5 days and 6-9 days AEWs from 700hPa meridional wind component over West Africa. The capability of RCA4 to reproduce the rainfall climatology, extreme rainfall events, the characteristics of AEWs and the contribution of AEWs to extreme rainfall events over the region during the past climate (1971-2005) was examined and quantified using statistical analysis. The future changes (2031-2065) in these parameters were projected for the RCP4.5 and RCP8.5 climate-change scenarios. The results of the study show that RCA4 gives a realistic simulation of the West African climate, including the annual rainfall pattern, the structure of AEWs, and the characteristics of the African Easterly Jet that feeds AEWs. The bias in the simulated threshold of extreme rainfall is within the uncertainty of the observed values. The model also captures the link between the structure of AEWs and the rainfall pattern over West Africa, and shows that the percentage contribution of AEWs to extreme rainfall events over the region ranges from 20 to 60%, as depicted by reanalysis data. For the RCP4.5 and RCP8.5 scenarios, the RCA4 ensemble mean projects a future increase in annual rainfall and in the frequency and intensity of extreme rainfall events over the sub-continent, but the increase is generally higher for the RCP8.5 scenario. It also projects a decrease in the frequency of rain days, no changes in the structure of the AEWs, and an increase in the variance of the waves. However, the simulations from the ensemble mean shows no substantial changes in the contribution of AEWs to the extreme rainfall events, suggesting that the increase in the frequency and intensity of the extreme rainfall events may not be attributable to the changes in AEWs. The study's application is in understanding and mitigating the future impact of climate extremes over West Africa.
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Tagliaferri, Lorenza. "Probabilistic Envelope Curves for Extreme Rainfall Events - Curve Inviluppo Probabilistiche per Precipitazioni Estreme." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amslaurea.unibo.it/99/.
Повний текст джерелаАнотація:
A regional envelope curve (REC) of flood flows summarises the current bound on our experience of extreme floods in a region. RECs are available for most regions of the world. Recent scientific papers introduced a probabilistic interpretation of these curves and formulated an empirical estimator of the recurrence interval T associated with a REC, which, in principle, enables us to use RECs for design purposes in ungauged basins.
The main aim of this work is twofold. First, it extends the REC concept to extreme rainstorm events by introducing the Depth-Duration Envelope Curves (DDEC), which are defined as the regional upper bound on all the record rainfall depths at present for various rainfall duration. Second, it adapts the probabilistic interpretation proposed for RECs to DDECs and it assesses the suitability of these curves for estimating the T-year rainfall event associated with a given duration and large T values. Probabilistic DDECs are complementary to regional frequency analysis of rainstorms and their utilization in combination with a suitable rainfall-runoff model can provide useful indications on the magnitude of extreme floods for gauged and ungauged basins.
The study focuses on two different national datasets, the peak over threshold (POT) series of rainfall depths with duration 30 min., 1, 3, 9 and 24 hrs. obtained for 700 Austrian raingauges and the Annual Maximum Series (AMS) of rainfall depths with duration spanning from 5 min. to 24 hrs. collected at 220 raingauges located in northern-central Italy. The estimation of the recurrence interval of DDEC requires the quantification of the equivalent number of independent data which, in turn, is a function of the cross-correlation among sequences. While the quantification and modelling of intersite dependence is a straightforward task for AMS series, it may be cumbersome for POT series. This paper proposes a possible approach to address this problem.
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Zambrana, Veroska Dueñas. "Análise numérica da influência de chuvas extremas na estabilidade de taludes." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3145/tde-13082015-111647/.
Повний текст джерелаАнотація:
Escorregamentos de taludes no Sudeste do Brasil são causados principalmente, pelo efeito da água proveniente das chuvas. Nos últimos anos, vem se incrementando o número de desastres naturais, ao passo são registradas mudanças climáticas, que podem exercer influência na ocorrência de chuvas extremas. Muitas encostas permanecem grande parte do ano com o solo em estado não saturado, porém variações nas condições ambientais podem ocasionar mudanças bruscas da sucção, reduzindo ou até mesmo eliminando-a e gerando pressões neutras positivas. A dissertação apresenta, um estudo sobre a influência das chuvas, consideradas extremas, no processo de infiltração e de este nos eventos de escorregamentos, considerados catastróficos pela sua dimensão, e que causaram prejuízos ambientais, econômicos e sociais no Brasil. Para o estudo foram selecionados dois eventos de escorregamentos translacionais rasos relativamente típicos, considerados catastróficos, um deles aconteceu na região da Serra de Cubatão em janeiro do ano 1985, e o outro na Região Serrana do Rio de Janeiro em janeiro de 2011. Estes dois eventos apresentaram características de precipitações e mecanismos de escorregamentos próprios, que permitem ilustrar os diferentes mecanismos atuantes em cada caso.Landslide in southeastern Brazil, are mainly caused by the effect of water from rainfall in infiltration process, in recent years has been increasing the number of natural disasters, while climate change that may exercising influence on the occurrence of extreme rainfall are recorded . Many slopes remain a large part of the year with unsaturated soil condition; however, changes in environmental conditions can cause sudden changes of suction, reducing or even deleting it and generate positive pore pressures. This dissertation presents a study about the influence of rainfall, considered extreme in the infiltration process and this one in the events regarded by their size of catastrophic landslides, which caused environmental, economic and social losses in Brazil. For the study were selected two events of shallow translational landslides relatively typical, considered catastrophic, one of them occurred in the Serra de Cubatão region on January 1985 and the other in the mountainous region of Rio de Janeiro on January 2011. Both events exhibit characteristics of rainfall and sliding mechanisms themselves, allowing illustrate the different mechanisms active in each case.
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Slinskey, Emily Anne. "Assessment of Observational Uncertainty in Extreme Precipitation Over the Continental United States." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4450.
Повний текст джерелаАнотація:
An extreme precipitation categorization scheme, developed to temporally and spatially visualize and track the multi-scale variability of extreme precipitation climatology, is introduced over the continental United States and used as the basis for an observational dataset intercomparison. The categorization scheme groups three-day precipitation totals exceeding 100 mm into five precipitation categories, or "P-Cats". To assess observational uncertainty across a range of precipitation measurement approaches, we compare in situ station data from the Global Historical Climatology Network-Daily (GHCN-D), satellite derived data from the Tropical Rainfall Measuring Mission (TRMM), gridded station data from the Parameter-elevation Regression on Independent Slopes Model (PRISM), global reanalysis from the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA 2), and regional reanalysis from the North American Regional Reanalysis (NARR). While all datasets capture the principal spatial patterns of extreme precipitation climatology, results show considerable variability across the five-platform suite in P-Cat frequency, spatial extent, and magnitude. Higher resolution datasets, PRISM and TRMM, most closely resemble GHCN-D and capture a greater frequency of high-end totals relative to lower resolution products, NARR and MERRA-2. When all datasets are regridded to a common coarser grid, differences persist with datasets originally constructed at a high resolution maintaining the highest frequency and magnitude of P-Cats. Potential future applications of this scheme include tracking change in P-Cats over space and time, climate model evaluation, and assessment of model projected change.
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Alias, Nor Eliza Binti. "IMPROVING EXTREME PRECIPITATION ESTIMATES CONSIDERING REGIONAL FREQUENCY ANALYSIS." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192162.
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Youngkyu, Kim. "Analyzing Uncertainty in Probable Maximum Precipitation Estimation using the Moisture Maximization Method." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263625.
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Suyanto, Adhi. "Estimating the exceedance probabilities of extreme floods using stochastic storm transportation and rainfall - runoff modelling." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386794.
Повний текст джерелаАнотація:
Methods of estimating floods with return periods of up to one hundred years are reasonably well established, and in the main rely on extrapolation of historical flood data at the site of interest. However, extrapolating the tails of fitted probability distributions to higher return periods is very unreliable and cannot provide a satisfactory basis for extreme flood estimation. The probable maximum flood concept is an alternative approach, which is often used for critical cases such as the location of nuclear power plants, and is viewed as a consequence of a combination of a probable maximum precipitation with the worst possible prevailing catchment conditions. Return periods are not usually quoted although they are implicitly thought to be of the order of tens of thousand of years. There are many less critical situations which still justify greater flood protection than would be provided for an estimated one-hundred year flood. There is therefore a need for techniques which can be used to estimate floods with return periods of up to several thousand years. The predictive approach adopted here involves a combination of a probabilistic storm transposition technique with a physically-based distributed rainfall-runoff model. Extreme historical storms within a meteorologically homogeneous region are, conceptually, moved to the catchment of interest, and their return periods are estimated within a probabilistic framework. Known features of storms such as depth, duration, and perhaps approximate shape will, together with catchment characteristics, determine much of the runoff response. But there are other variables which also have an effect and these include the space-time distribution of rainfall within the storm, storm velocity and antecedent catchment conditions. The effects of all these variables on catchment response are explored.
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McGuire, Luke A., Francis K. Rengers, Jason W. Kean, Jeffrey A. Coe, Benjamin B. Mirus, Rex L. Baum, and Jonathan W. Godt. "Elucidating the role of vegetation in the initiation of rainfall-induced shallow landslides: Insights from an extreme rainfall event in the Colorado Front Range." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/621986.
Повний текст джерелаАнотація:
More than 1100 debris flows were mobilized from shallow landslides during a rainstorm from 9 to 13 September 2013 in the Colorado Front Range, with the vast majority initiating on sparsely vegetated, south facing terrain. To investigate the physical processes responsible for the observed aspect control, we made measurements of soil properties on a densely forested north facing hillslope and a grassland-dominated south facing hillslope in the Colorado Front Range and performed numerical modeling of transient changes in soil pore water pressure throughout the rainstorm. Using the numerical model, we quantitatively assessed interactions among vegetation, rainfall interception, subsurface hydrology, and slope stability. Results suggest that apparent cohesion supplied by roots was responsible for the observed connection between debris flow initiation and slope aspect. Results suggest that future climate-driven modifications to forest structure could substantially influence landslide hazards throughout the Front Range and similar water-limited environments where vegetation communities may be more susceptible to small variations in climate.
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Hermelin, Samuel. "Differences in consequences between peak arrivals and movement directions of an extreme rainfall in flood modeling." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232680.
Повний текст джерелаАнотація:
To avoid damages and costs for the society due to flooding is it important to be able to model accurate rain scenarios. Due to climate change is it thought that there will be more heavy rainfalls in the future which will increase the risk for flooding. This master thesis will therefore look at the parameters that affect the risk for flooding with focus on raincloud movement and peak arrivals. Earlier research has shown that different directions of the rain will affect the flooding risk differently. Generally will a rain that has the same direction as the downstream flow lead to a higher risk for flooding. The peak arrival time has also shown to lead to different results were a late peak arrival seems to lead to a higher risk for flooding. There is usually too little time and costly to test different movement and peak arrival scenarios, so this report will focus on which of these parameters that have the greatest flooding impact and largest internal variation. MIKE 21 (created by DHI) is the software used to model the different rain scenarios. The rain types used to test the different scenarios will be a uniform rain, a traditional CDS-rain and five rain shapes that are based on empirical rain types created by SMHI. The shape of the empirical rains is based on several studies from measured rain events with weather radar. Weather radar have become a fundamental tool in weather forecasting because it can collect data in near real time and also measure the spatial variation inside the rainfall. These seven mentioned rain types will not be moving, and the rain will have the same spatial intensity over the study area. They will be compared both to each other but also to a CDS-rain that will move over the study area in 4 different directions (north-south, east-west, south - north and west - east). The different directions gave all very similar results while there was a larger difference between the rain types with different peak arrivals. The peak-value seems to be an important factor when it comes to flooding risk based on the results in this report. The constant uniform rain had the lowest amount of flooded areas while the CDS-rain (which had the highest peak) affected the area the most.
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Zhang, Huan Verfasser], and Klaus [Akademischer Betreuer] [Fraedrich. "Extreme rainfall events in simulations, theory and related large-scale dynamic processes / Huan Zhang. Betreuer: Klaus Fraedrich." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1051435463/34.
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Medeiros, Vanesca Sartorelli. "Análise estatística de eventos críticos de precipitação relacionados a desastres naturais em diferentes regiões do Brasil." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3147/tde-04102013-113054/.
Повний текст джерелаАнотація:
A dissertação apresenta um estudo das chuvas extremas relacionadas a quatro desastres naturais ocorridos no Brasil: as inundações do Vale do Itajaí SC, em novembro de 2008, a inundação histórica de São Luís do Paraitinga - SP, em janeiro de 2010, as inundações ocorridas no Vale do Mundaú AL, em junho de 2010 e as inundações e escorregamentos da Região Serrana - RJ, em janeiro de 2011. As chuvas catastróficas foram analisadas através de estatísticas básicas dos dados dos pluviômetros localizados nas regiões. No Vale do Itajaí, as chuvas registradas nos dias 23 e 24 de novembro foram elevadas, atingindo valores acima de 250 mm. Na estação Blumenau, choveu 243,5 mm e 250,9 mm nesses. Na estação localizada em São Luís do Paraitinga, choveu apenas 64,7 mm no dia 1 de janeiro de 2010, quando ocorreu a inundação. Porém, foram observados 205,7 mm em uma das estações localizadas em Cunha. Nesse caso, o elevado volume precipitado na cabeceira da bacia deflagrou as inundações observadas nos dois municípios. No Vale do Mundaú e Paraíba, choveu cerca de 200 mm no dia 5 de junho, em duas das seis estações analisadas. O elevado volume precipitado no dia 5, combinado com as chuvas ocorridas no período de 17 a 19, pode ter causado as inundações observadas no dia 19 nessas bacias. Os dados indicaram que, na Região Serrana do RJ, as inundações e escorregamentos foram causados pela chuva extrema ocorrida nos dias 11 e 12 de janeiro de 2011, que ultrapassou 270 mm no intervalo de 24 h em uma das estações. As chuvas acumuladas nos meses que antecedem os eventos e a alta declividade contribuíram para a saturação do solo e posteriores escorregamentos. Os eventos pluviométricos, classificados através do SPI resultaram, na maioria das estações, chuvas severas ou chuvas extremas A vulnerabilidade das regiões, onde inúmeras habitações estão localizadas em áreas de risco, também foi determinante para que os desastres acontecessem. Outros eventos de magnitude elevada foram observados anteriormente, o que indica que estes eventos são característicos das regiões estudadas. Constatou-se que as regiões analisadas estão sujeitas a chuvas extremas com frequência relativamente alta, muito embora tenha sido observado, em alguns casos, certo grau de raridade nesses eventos. Portanto, nessas áreas devem ser adotadas medidas regionais no sentido de disciplinar o uso e ocupação do solo e reduzir os riscos dos desastres. É fundamental buscar medidas de adaptação da ocupação dessas áreas, considerando o regime hidrológico dessas regiões.The paper presents a study of extreme rainfall related to four natural disasters occurring in Brazil: the floods in Itajaí Valley, state of Santa Catarina, in November, 2008; the historic flood in São Luís do Paraitinga, state of São Paulo, in January, 2010; the floods in Mundaú Valley, state of Alagoas, in June, 2010; and the floods and landslides in the mountainous region of Rio de Janeiro in January, 2011. The catastrophic rains were analyzed through basic statistical data collected from rain gauges located in those regions. In Itajaí Valley, extremely high rainfalls exceeding 250 mm were recorded on November 23 and 24. In Blumenau, it rained 243.5 mm and 250.9 mm on the same days. At the station located in São Luís do Paraitinga, it rained just 64.7 mm on January 1, 2010, when the flood occurred. However, 205.7 mm were observed in one of the stations located in Cunha. In this case, the high volume of rainfall at the headwater of the basin triggered flooding observed in these two cities. In the valleys of Mundaú and Paraíba, it rained nearly 200 mm on June 5, in two of the six stations analyzed. The high volume of rainfall on June 5, combined with the rains from the 17th to the 19th, may have led to the floods in these basins on June 19. The data indicated that, in the mountainous region of Rio de Janeiro, the flooding and landslides were caused by massive rainfall on January 11 and 12, 2011, which exceeded 270 mm within a period of 24 hours in one of the stations. The rainfall accumulated in the months prior to the events and the high sloping land contributed to soil saturation and subsequent landslides. The rainfall events, sorted through the SPI, resulted in severe or extreme rains in most of the stations. The vulnerability of the regions, which include many homes located in hazardous areas, was also crucial for the disasters to happen. Other major events were previously observed, which indicates that these events are characteristic of the studied regions. It was noted that the analyzed regions are subject to extreme rains with a relatively high frequency, although in some cases these events have demonstrated to be somewhat rare. Therefore, in these areas, region-based measures should be adopted with a view to regulating the use and occupation of the soil and reducing risk of disasters. It is essential to seek adaptation measures of occupation of these areas, considering their hydrological regime.
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Wooten, Rebecca Dyanne. "Statistical environmental models : hurricanes, lightning, rainfall, floods, red tide and volcanoes." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001824.
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Boers, Niklas [Verfasser], Jürgen [Akademischer Betreuer] Kurths, José A. [Akademischer Betreuer] Marengo, and Thomas [Akademischer Betreuer] Stemler. "Complex network analysis of extreme rainfall in South America / Niklas Boers. Gutachter: Jürgen Kurths ; José A. Marengo ; Thomas Stemler." Berlin : Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://d-nb.info/1072723573/34.
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Kalantari, Zahra. "Road structures under climate and land use change : Bridging the gap between science and application." Doctoral thesis, KTH, Mark- och vattenteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140631.
Повний текст джерелаАнотація:
Future changes in climate and land use are likely to affect catchment hydrological responses and consequently influence the amount of runoff reaching roads. Blockages and damage to under-dimensioned infrastructure can be extremely costly for the regions affected. This study aims to produce scientifically well-founded suggestions on adaptation of road drainage systems to climate changes resulting in more frequent floods. This thesis demonstrates the need to integrate aspects of climate change and land use impacts into the planning and practice of road construction and maintenance in Sweden. Tools such as hydrological models are needed to assess impacts on discharge dynamics. Identifying a ‘best’ practically performing hydrological model is often difficult due to the potential influence of modeller subjectivity on calibration procedure, parameter selection, etc. Hydrological models may need to be selected on a case-by-case basis and have their performance evaluated on an application-by-application basis. The work presented here began by examining current practice for road drainage systems in Sweden. Various hydrological models were then used to calculate the runoff from a catchment adjacent to a road and estimate changes in peak discharge and total runoff resulting from simulated land use measures. Overall, the results indicate that the specific effect of land use measures on catchment discharge depend on their spatial distribution and on the size and timing of storm events. Scenarios comprising a changing climate up to 2050 or to 2100 and forest clear-cutting were used to determine whether the current design of road drainage construction is sufficient for future conditions. Based on the findings, the approach developed can be used for similar studies, e.g. by the Swedish Transport Administration in dimensioning future road drainage structures to provide safe and robust infrastructure. Furthermore, a statistical method was developed for estimating and mapping flood hazard probability along roads using road and catchment characteristics. The method allows flood hazards to be estimated and provides insight into the relative roles of landscape characteristics in determining road-related flood hazards. Overall, this method provides an efficient way to estimate flooding hazards and to inform the planning of future roadways and the maintenance of existing roadways.QC 20140130
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Andrys, Julia. "Regional climate projections for the South West of Western Australia to simulate changes in mean and extreme rainfall and temperature." Thesis, Andrys, Julia (2016) Regional climate projections for the South West of Western Australia to simulate changes in mean and extreme rainfall and temperature. PhD thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/34081/.
Повний текст джерелаАнотація:
The southwest of Western Australia (SWWA) is an area of significant agricultural production and an internationally recognised biodiversity hotspot. The region has experienced marked rainfall reductions over the last four decades and there is uncertainty as to the extent of future changes to the hydrological regime. Hence, there is a need for regional climate information in SWWA to better inform climate adaptation strategies for several key sectors, including agriculture and forestry. The overarching aim of this project is to provide such information, with a focus on changes in rainfall and temperature extremes.
The Weather Research and Forecasting (WRF) model was used as a regional climate model for SWWA. Given the known sensitivity of WRF to physics options and driving data, the most appropriate physical parameterisations were tested on a yearly time-scale. Based on these findings, a 30-year climatology was produced for SWWA (1981-2010) at a 5 km resolution by downscaling ERA-Interim reanalysis. Comparisons against observations showed that the model was able to simulate the daily, seasonal and annual variation of temperature and precipitation well, including extreme events. The model was then used to downscale an ensemble of 4 general circulation models (GCMs) for the historical period (1970- 1999) and compared against both observations and the GCMs. WRF was shown to add value to the GCM data for 3 out of the 4 GCMs evaluated, particularly in the spatio-temporal distribution of winter rainfall.
Finally, the ensemble was run from 2030-2059 to examine projected climate change in SWWA. Results project that maximum temperature extremes will increase, consistent with mean changes however the variance of maximum temperatures is not projected to change significantly. While mean minimum temperatures are not projected to increase as much as maximum temperatures, there is strong evidence that the variability of minimum temperatures will increase. This has the potential to raise the likelihood of night time temperature extremes. Simulations project a reduction in rainfall, particularly during winter. This decline is related to fewer frontal systems traversing the SWWA and hence fewer rain days. The study found no evidence to suggest that the intensity of rain bearing winter storms is likely to change.
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Sousa, Antônio José da Silva. "Eventos extremos de precipitação no leste da Amazônia." Universidade Federal de Alagoas, 2010. http://repositorio.ufal.br/handle/riufal/871.
Повний текст джерелаАнотація:
The aim of this study was to characterize the extreme events of rainfall in Eastern
Amazon, to analyze on ocean-atmosphere conditions in global scale associated with
intense occurrence periods of these events, to contribute for temporal variation
comprehension of rainfall extreme events, as well as of determinant phenomena to its
occurrence and to make further projections. For this purpose, Pluviometric Precipitation
stations data from Brazilian National Institute for Meteorology (INMET) located in
Belém, Breves, Altamira, Tucuruí and Marabá; and monthly data of precipitation from
Delaware University (UDEL). In addition, available meteorological series at
ESRL/PSD, particularly, sea surface temperature; u and v components; outgoing long
wave radiation; atmospheric vertical movements; divergence fields; satellite images and
oceanic and atmospheric climatic indices as Multidecadal Atlantic Oscillation, Pacific
Decadal Oscillation (PDO), North Atlantic Oscillation, South Oscillation and
Multivariated ENOS index. The methodology has included statistical techniques for
rainfall analysis and behavior, as well as major phenomena that influence its annual
regime, and events diagnostic as well. It was made class distribution of daily rainfall in
Belém-PA, Eastern Amazon, and was clear that rainfall yearly total high values in that
region were resulting from extreme events of rainfall that contributed, in average, with
37% from rain yearly total. These extreme events corresponded to 10% from total
values of rainy days. There was a rising trend of these events in the last 10 years,
attributed to upper troposphere cooling during that beginning of new PDO cold phase.
Oceanic and atmospheric indices from Pacífic Ocean have shown to be a valuable tool
for prediction of periods with extreme event occurrences. Trade winds, and mainly the
sea surface temperature, were determinant factors for extreme events occurrence and
development in Eastern Amazon, wavelets transform analysis has shown the energy and
annual cycle present in precipitation regime of this region, as well as influence of high
frequency phenomena as ENOS at rainy season of analyzed stations. Climate
perspectives indicated that PDO is already in the new cold phase and its permanence is
not known, much less its causes. However, if that new phase remain for more 15 to 20
years, certainly there will be rise in rainfall extreme events in Eastern Amazon, due to
slowly cooling of upper troposphere, resulting in most vertical development of
cumulonimbus clouds, responsible by high total values of rainfall.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O objetivo principal desse estudo foi fazer a caracterização dos eventos extremos de precipitação no leste da Amazônia, a análise das condições oceano-atmosfera em escala global associadas a períodos com intensa ocorrência desses eventos, contribuir para a compreensão da variação temporal dos eventos extremos de chuva, assim como dos fenômenos determinantes para a sua ocorrência e fazer projeções futuras. Para tal, foram utilizados dados de precipitação pluviométrica do Instituto Nacional de Meteorologia (INMET) das estações de Belém, Breves, Altamira, Tucuruí e Marabá e dados de precipitação mensal da Universidade de Delaware (UDEL). Em adição a isso, séries de variáveis meteorológicas disponíveis no ESRL/PSD, em especial, temperatura da superfície do mar, componentes u e v do vento, radiação de onda longa emergente, movimentos verticais atmosféricos, campos de divergência, imagens de satélite e índices climáticos oceânicos e atmosféricos, como a Oscilação Multidecadal do Atlântico, Oscilação Decadal do Pacifico (ODP), Oscilação do Atlântico Norte, Oscilação Sul e Índice Multivariado de ENOS. A metodologia incluiu técnicas estatísticas para análise e comportamento da precipitação, assim como os fenômenos que mais influenciam em seu regime anual, além dos diagnósticos dos eventos. Foi elaborada a distribuição de classes da precipitação diária em Belém (PA), leste da Amazônia, e ficou claro que os altos totais anuais de chuva nessa região foram decorrentes de eventos extremos de precipitação, que contribuíram, em média, com 37% do total anual de chuva. Esses eventos extremos representaram 10% dos totais de dias chuvosos. Houve uma tendência de aumento desses eventos nos últimos 10 anos, o que foi atribuído ao resfriamento da troposfera superior durante esse início da nova fase fria da ODP. Os índices oceânicos e atmosféricos do Oceano Pacifico, mostraram ser uma ferramenta valiosa para a previsão de períodos com ocorrência de eventos extremos. Os ventos Alísios, e principalmente a temperatura da superfície do mar, foram fatores determinantes para o desenvolvimento e ocorrência de eventos extremos no leste da Amazônia, A análise da Transformada de Ondeleta (TO) mostrou a energia e o ciclo anual presente no regime de precipitação dessa região, assim como a influência de fenômenos de alta freqüência como o ENOS no período chuvoso das estações analisadas. As perspectivas climáticas indicaram que a ODP já está em sua nova fase fria. Não se sabe por quanto tempo a ODP irá permanecer em sua nova fase, muito menos as suas causas, porém, se ela perdurar por mais 15 a 20 anos, que é o esperado, certamente haverá um aumento nos eventos extremos de chuva na região Amazônica, devido ao paulatino resfriamento da troposfera superior, resultando em maior desenvolvimento vertical de nuvens tipo cumulonimbo, responsável pelos altos totais pluviométricos.
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Luu, Nhat Linh. "The role of human-induced climate change on extreme convective precipitation events in the south of France : a high-resolution model simulation approach." Electronic Thesis or Diss., université Paris-Saclay, 2020. http://www.theses.fr/2020UPASV018.
Повний текст джерелаАнотація:
La zone France-Méditerranée est fréquemment exposée à de fortes précipitations en automne dont l'accumulation quotidienne peut parfois dépasser 300 millimètres. Quelques études montrent une tendance à l'augmentation de la fréquence et de l'intensité de ces événements (par exemple Vautard et al., 2015 ; Ribes et al., 2019). Cependant, une attribution formelle des événements extrêmes qui lie ces changements au changement climatique induit par l'homme pour cette région n'a jamais été faite. Ce sujet de thèse vise à quantifier le rôle du changement climatique induit par l'homme dans l'altération des propriétés statistiques des précipitations convectives extrêmes survenant sur la région France-Méditerranée, en se concentrant sur la chaîne de montagnes des Cévennes et en utilisant pour la première fois une approche de modèle à haute résolution incluant un modèle permettant la convection. J'analyse d'abord l'ensemble EURO-CORDEX, qui comprend différentes combinaisons de modèles climatiques globaux et de modèles climatiques régionaux. Ensuite, j'ai effectué une série de simulations numériques avec le modèle WRF à une résolution permettant la convection. J'ai également comparé les simulations avec les observations et les ré-analyses à haute résolution. Les résultats montrent que les modèles régionaux peuvent reproduire des événements extrêmes de pluie convective avec une meilleure concordance avec les observations en augmentant leur résolution horizontale, en particulier à une résolution permettant la convection (environ 3 km). En utilisant ces simulations, je montre que le changement climatique induit par l'homme rend les précipitations quotidiennes et trihoraires sur 100 ans au moins deux fois plus probables dans le climat actuel. Les résultats suggèrent également la nécessité d'utiliser une approche multi-modèle pour réduire les incertitudes dans ce type d'étude d'impactThe France-Mediterranean area is frequently exposed to heavy precipitation events in the autumn whose daily accumulation can sometimes exceed 300 millimeters. There are a few studies showing the increasing trend in the frequency and intensity of these events (e.g. Vautard et al., 2015; Ribes et al., 2019). However, a formal extreme event attribution that links those changes to human-induced climate change for this area has never been done. This PhD subject aims at quantifying the role of human-induced climate change in altering the statistical properties of extreme convective precipitation event occurring over the France-Mediterranean focusing on the Cevennes mountain range and using a high-resolution model approach including convection-permitting model for the first time. I first analyze the EURO-CORDEX ensemble, which includes different combinations of global climate models and regional climate models. Then I conducted a set of numerical simulations with the WRF model at a convection-permitting resolution. I also compared the simulations with observations and high-resolution re-analyses. The results show that regional models can reproduce extreme convective rainfall events with better agreement with observations by increasing their horizontal resolution, especially to convection-permitting resolution (approx. 3 km). By using these simulations, I show that human-induced climate change consistently makes the 100-year 3-hourly and daily precipitation event at least 2 times more likely under current climate. The results also suggest the need of using multi-model approach to reduce the uncertainties in this type of impact study
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Rupi, Alberto Pio. "Analisi meteorologica di eventi con precipitazione intensa nell'Italia Centrale." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Знайти повний текст джерелаАнотація:
In this work we analyze five events of intense precipitation that affected Central Italy between 2011 and 2015. These events caused important flood phenomena, with a significant impact on both the economy and people. This study mainly uses data from ERA5, the latest reanalysis produced by the ECMWF (European Center for Medium-range Weather Forecast), in addition to data from the meteorological network managed by Centro Funzionale of Protezione Civile d’Abruzzo. In the first part is reported an overview of the general issues that characterize the study of intense precipitation events, with a deepening of some recently analyzed cases. Subsequently the data and tools used are reported, with a description of the events studied and the method of investigation. We then go to analyze the synoptic framework in which the event developed and to investigate the causes that generated it. Finally, the precipitation pattern was studied and the degree of reproducibility by the ERA5 reanalysis was tested through a comparison with the meteorological network.
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Tusher, Md Didarul Alam. "Impact of Extreme Rainfall Event over Swedish Urban Catchments : A study on catchment characterization in the context of Aerial Reduction Factor and storm movement." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266469.
Повний текст джерелаАнотація:
The design practices of urban hydraulic structures are required to be based on enough safety measures in addition to cost efficiency for sustainable development. Overestimation of catchment runoff generated from a storm event can increase the project cost unnecessarily. For urban pluvial studies, use of Aerial Reduction Factor (ARF) helps to estimate the probable precipitation intensity inside a catchment. By understanding the necessity of using ARF from a national context and applying it in present design practices can pave the way towards sustainable design practices. In this study the applicability of ARF from Swedish urban context was analyzed. The urban catchments for fifty biggest Swedish cities were delineated and the catchment parameters were analyzed. Application of ARF depends on the size of catchment. To experience a significant reduction in catchment outlet discharge, the minimum catchment area for application of ARF was reported as 5 km2. According to the analyzed parameters, ninety percent of catchment sizes in Swedish urban area were found less than 5 km2, which are quite small in respect of ARF applicability. It was realized from the analysis that application of ARF within a single catchment is not much necessary for pluvial studies in Swedish urban catchments due to catchment properties. In addition to rainfall intensity, rainfall movement also changes the runoff behavior from a catchment. When catchment’s flow velocity and direction through main channel and storm moving velocity and direction over the channel coincides with each other, then the outlet peak discharge magnifies in comparison to a stationery storm, known as resonance effect. The impact of storm movement over catchment was analyzed using HEC-HMS modelling with varying storm movement velocity over catchment. The analysis was performed on 12 catchments of different size and flow velocity. It was found that the peak discharge can increase up to 46 percent depending upon catchment characteristics. The flow velocity through all the delineated catchments of fifty cities were calculated using USDA’s NRCS TR-55 method and then compared with usual storm moving velocities in Sweden. It was found that, due to flat nature of Swedish urban areas, the flow velocities are very low (<2 m/s) in compare to average storm velocity (8 m/s), portraying the fact that there is limited probability that these velocities will coincide. But for any area where storm velocity is normally low, resonance effect can happen. Precise analysis based on local conditions are suggested while modelling a particular area, since impact of resonance effect can overrun the design considerations.