Comparison of the Calculated Drought Return Periods Using Tri-variate and Bivariate Copula Functions under Climate Change Condition

Abstract Concerning the various effects of climate change on intensifying extreme weather phenomena all around the world, studying its possible consequences in the following years has attracted the attention of researchers. As the drought characteristics identified by drought indices are highly significant in investigating the possible future drought, the Copula function is employed in many studies. In this study, the two- and three-variable Copula functions were employed for calculating the return period of drought events for the historical, the near future, and the far future periods. The results of considering the two- and three-variable Copula functions were separately compared with the results of the calculated Due to the high correlation between drought characteristics, bivariate and trivariate of Copula functions were applied to evaluate the return periods of the drought. The most severe historical drought was selected as the benchmark, and the drought zoning map for the GCM models was drawn. The results showed that severe droughts can be experienced, especially in the upper area of the basin where the primary water resource is located. Also, the nature of the drought duration plays a decisive role in the results of calculating the return periods of drought events.

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Comparison of the Calculated Drought Return Periods Using Tri-variate and Bivariate Copula Functions under Climate Change Condition

10.22541/au.160982220.05390474/v1 ◽

2021 ◽

Author(s):

Elahe Motevali Bashi Naeini ◽

Ali Mohammad Akhondali ◽

Fereydoun Radmanesh ◽

Jahangir Abedi-Koupai ◽

Shahrokh Soltaninia

Keyword(s):

Climate Change ◽

Decisive Role ◽

Copula Function ◽

Drought Indices ◽

Return Periods ◽

Copula Functions ◽

Drought Duration ◽

Drought Characteristics ◽

Primary Water ◽

Bivariate Copula

Concerning the various effects of climate change on intensifying extreme weather phenomena all around the world, studying its possible consequences in the following years has attracted the attention of researchers. As the drought characteristics identified by drought indices are highly significant in investigating the possible future drought, the Copula function is employed in many studies. In this study, the two- and three-variable Copula functions were employed for calculating the return period of drought events for the historical, the near future, and the far future periods. The results of considering the two- and three-variable Copula functions were separately compared with the results of the calculated Due to the high correlation between drought characteristics, bivariate and trivariate of Copula functions were applied to evaluate the return periods of the drought. The most severe historical drought was selected as the benchmark, and the drought zoning map for the GCM models was drawn. The results showed that severe droughts can be experienced, especially in the upper area of the basin where the primary water resource is located. Also, the nature of the drought duration plays a decisive role in the results of calculating the return periods of drought events.

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Comparison of the Calculated Drought Return Periods Using Tri-variate and Bivariate Copula Functions Under Climate Change Condition

Water Resources Management ◽

10.1007/s11269-021-02965-6 ◽

2021 ◽

Author(s):

Elaheh Motevali Bashi Naeini ◽

Ali Mohammad Akhoond-Ali ◽

Fereydoun Radmanesh ◽

Jahangir Abedi Koupai ◽

Shahrokh Soltaninia

Keyword(s):

Climate Change ◽

Return Periods ◽

Copula Functions ◽

Change Condition ◽

Bivariate Copula

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Copula-Based Drought Monitoring and Assessment According to Zonal and Meridional Temperature Gradients

Atmosphere ◽

10.3390/atmos12081066 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1066

Author(s):

Abudureymjang Otkur ◽

Dian Wu ◽

Yin Zheng ◽

Jong-Suk Kim ◽

Joo-Heon Lee

Keyword(s):

Kendall Test ◽

Accurate Method ◽

Copula Function ◽

Temperature Gradients ◽

Drought Severity ◽

Copula Functions ◽

Drought Duration ◽

Drought Assessment ◽

Drought Characteristics ◽

Drought Duration And Severity

Drought is one of the most severe natural disasters. However, many of its characteristic variables have complex nonlinear relationships. Therefore, it is difficult to construct effective drought assessment models. In this study, we analyzed regional drought characteristics in China to identify their relationship with changes in meridional and zonal temperature gradients. Drought duration and severity were extracted according to standardized precipitation evapotranspiration index (SPEI) drought grades. Trends in drought duration and severity were detected by the Mann-Kendall test for the period of 1979–2019; they showed that both parameters had been steadily increasing during that time. Nevertheless, the increasing trend in drought severity was particularly significant for northwest and southwest China. A composite analysis confirmed the relationships between drought characteristics and temperature gradients. The northwest areas were relatively less affected by temperature gradients, as they are landlocked, remote from the ocean, and only slightly influenced by the land–ocean thermal contrast (LOC) and the meridional temperature gradient (MTG). The impacts of LOC and MTG on drought duration and severity were positive in the southwest region of China but negative in the northeast. As there was a strong correlation between drought duration and severity, we constructed a 2D copula function model of these parameters. The Gaussian, HuslerReiss, and Frank copula functions were the most appropriate distributions for the northeast, northwest, and southwest regions, respectively. As drought processes are highly complex, the present study explored the internal connections between drought duration and severity and their responses to meteorological conditions. In this manner, an accurate method of predicting future drought events was developed.

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Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens

Water ◽

10.3390/w12071938 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1938 ◽

Cited By ~ 1

Author(s):

Christina M. Botai ◽

Joel O. Botai ◽

Abiodun M. Adeola ◽

Jaco P. de Wit ◽

Katlego P. Ncongwane ◽

...

Keyword(s):

South Africa ◽

Gaussian Copula ◽

Dependence Structure ◽

Drought Risk ◽

Eastern Cape Province ◽

Return Periods ◽

Eastern Cape ◽

Copula Functions ◽

Drought Duration ◽

Drought Duration And Severity

This research study was carried out to investigate the characteristics of drought based on the joint distribution of two dependent variables, the duration and severity, in the Eastern Cape Province, South Africa. The drought variables were computed from the Standardized Precipitation Index for 6- and 12-month accumulation period (hereafter SPI-6 and SPI-12) time series calculated from the monthly rainfall data spanning the last five decades. In this context, the characteristics of climatological drought duration and severity were based on multivariate copula analysis. Five copula functions (from the Archimedean and Elliptical families) were selected and fitted to the drought duration and severity series in order to assess the dependency measure of the two variables. In addition, Joe and Gaussian copula functions were considered and fitted to the drought duration and severity to assess the joint return periods for the dual and cooperative cases. The results indicate that the dependency measure of drought duration and severity are best described by Tawn copula families. The dependence structure results suggest that the study area exhibited low probability of drought duration and high probability of drought severity. Furthermore, the multivariate return period for the dual case is found to be always longer across all the selected univariate return periods. Based on multivariate analysis, the study area (particularly Buffalo City, OR Tambo and Alfred Zoo regions) is determined to have higher/lower risks in terms of the conjunctive/cooperative multivariate drought risk (copula) probability index. The results of the present study could contribute towards policy and decision making through e.g., formulation of the forward-looking contingent plans for sustainable management of water resources and the consequent applications in the preparedness for and adaptation to the drought risks in the water-linked sectors of the economy.

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Climate Change Effects on Spatiotemporal Patterns of Hydroclimatological Summer Droughts in Norway

Journal of Hydrometeorology ◽

10.1175/2011jhm1357.1 ◽

2011 ◽

Vol 12 (6) ◽

pp. 1205-1220 ◽

Cited By ~ 31

Author(s):

Wai Kwok Wong ◽

Stein Beldring ◽

Torill Engen-Skaugen ◽

Ingjerd Haddeland ◽

Hege Hisdal

Keyword(s):

Climate Change ◽

General Circulation ◽

Dominant Role ◽

Summer Precipitation ◽

Meteorological Drought ◽

Threshold Level ◽

General Circulation Models ◽

Drought Duration ◽

Drought Characteristics ◽

The Impact

Abstract This study examines the impact of climate change on droughts in Norway. A spatially distributed (1 × 1 km2) version of the Hydrologiska Byråns Vattenbalansavdelning (HBV) precipitation-runoff model was used to provide hydrological data for the analyses. Downscaled daily temperature and precipitation derived from two atmosphere–ocean general circulation models with two future emission scenarios were applied as input to the HBV model. The differences in hydroclimatological drought characteristics in the summer season between the periods 1961–90 and 2071–2100 were studied. The threshold level method was adopted to select drought events for both present and future climates. Changes in both the duration and spatial extent of precipitation, soil moisture, runoff, and groundwater droughts were identified. Despite small changes in future meteorological drought characteristics, substantial increases in hydrological drought duration and drought affected areas are expected, especially in the southern and northernmost parts of the country. Reduced summer precipitation is a major factor that affects changes in drought characteristics in the south while temperature increases play a more dominant role for the rest of the country.

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Use of four drought indices for evaluating drought characteristics under climate change in Shaanxi, China: 1951–2012

Natural Hazards ◽

10.1007/s11069-014-1468-x ◽

2014 ◽

Vol 75 (3) ◽

pp. 2885-2903 ◽

Cited By ~ 49

Author(s):

Rengui Jiang ◽

Jiancang Xie ◽

Hailong He ◽

Jungang Luo ◽

Jiwei Zhu

Keyword(s):

Climate Change ◽

Drought Indices ◽

Drought Characteristics

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Multivariate drought risk analysis based on copula functions: a case study

Water Science & Technology Water Supply ◽

10.2166/ws.2020.153 ◽

2020 ◽

Vol 20 (6) ◽

pp. 2375-2388

Author(s):

Mohammadreza Seyedabadi ◽

Mohammadreza Kavianpour ◽

Saber Moazami

Keyword(s):

Return Period ◽

Drought Index ◽

Human Life ◽

Standardized Precipitation Index ◽

Drought Indices ◽

Drought Risk ◽

Severe Drought ◽

Copula Functions ◽

Drought Characteristics ◽

Multiple Variables

Abstract Drought is asserted as a natural disaster that encompasses vast territories for a long time and affects human life. Indicators are powerful tools for understanding this phenomenon. However, in order to get more information about the drought, multivariate indices were introduced for simultaneous evaluation of multiple variables. In this study, a combined drought index (CDI) based on three drought indices, the Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Standardized Water-level Index (SWI), is defined. Then, the Entropy method is used to determine the weight of each indicator. Among the calculated weights, SDI and SPI had the highest and lowest weight, respectively. The CDI is utilized to identify drought characteristics, such as duration and severity. In addition, the joint distribution function of drought characteristics is formed by copula functions and consequently the probability of different droughts is calculated. For the study area, data and information from eight regions located in Golestan province in the northern part of Iran are used to evaluate the performance of the proposed index. Four categories of drought were defined and their return period calculated. The shortest return period of severe drought was observed in the east and then in the west. In the south and center, the return period of severe drought was longer. Over the course of 30 years, all parts of the province experienced all drought categories.

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Markov Chain Models for Hydrological Drought Characteristics

Journal of Hydrometeorology ◽

10.1175/jhm-d-11-019.1 ◽

2012 ◽

Vol 13 (1) ◽

pp. 298-309 ◽

Cited By ~ 20

Author(s):

Dilek Eren Akyuz ◽

Mehmetcik Bayazit ◽

Bihrat Onoz

Keyword(s):

Markov Chain ◽

Markov Chain Model ◽

Second Order ◽

Chain Model ◽

Return Periods ◽

Annual Streamflow ◽

Drought Duration ◽

Drought Characteristics ◽

Markov Chain Models ◽

Order Markov Chain

Abstract Estimation of drought characteristics such as probabilities and return periods of droughts of various lengths is of major importance in drought forecast and management and in solving water resources problems related to water quality and navigation. This study aims at applying first- and second-order Markov chain models to dry and wet periods of annual streamflow series to reproduce the stochastic structure of hydrological droughts. Statistical evaluation of drought duration and intensity is usually carried out using runs analysis. First-order Markov chain model (MC1) for dry and wet periods is not adequate when autocorrelation of the original hydrological series is high. A second-order Markov chain model (MC2) is proposed to estimate the probabilities and return periods of droughts. Results of these models are compared with those of a simulation study assuming a lag-1 autoregressive [AR(1)] process widely used to model annual streamflows. Probability distribution and return periods of droughts of various lengths are estimated and compared with the results of MC1 and MC2 models using efficacy evaluation statistics. It is found that the MC2 model in general gives results that are in better agreement with simulation results as compared with the MC1 model. Skewness is found to have little effect on return periods except when autocorrelation is very high. MC1 and MC2 models are applied to droughts observed in some annual streamflow series, with the result that the MC2 model has a relatively good agreement considering the limited duration of the records.

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Practical tool for drought characteristics calculation

10.5194/egusphere-egu21-14328 ◽

2021 ◽

Author(s):

Mahyar Mottaghi Zadeh ◽

Maral Habibi

Keyword(s):

Quantitative Description ◽

Geographical Location ◽

Drought Indices ◽

Drought Severity ◽

Drought Condition ◽

Development Environment ◽

Drought Duration ◽

Software Application ◽

Drought Characteristics ◽

Drought Conditions

There are many ways to identify and monitor drought conditions. Scarcely are tools that calculate drought characteristics, The "SDF Calculator" works to bring monitoring tools to the public so they can assess drought conditions, this tool is used to assess and identify drought and its intensity.Drought severity refers to the absolute sum of consecutive SDI values below a given threshold level while drought duration is the number of consecutive months that SDI is below that threshold, and drought frequency is a number of months with drought condition (means SPI < -0.5 or any given threshold that is desire, the threshold of drought index is a value that an index faces to drought condition. In every index, this value can be changed. For example, in many indices, the threshold of drought starts from zero or less zero. In other words, when the value of an index is calculating then all the values located in the drought classes, refer to the severity of the drought.Droughts and exceptionally wet periods are regional phenomena, which are considered as major environmental extremes, especially in semiarid regions of the world. The development of severity-duration-frequency (SDF) relationships of droughts and wet periods is important in hydrological and climatic plannings in any country.In this study, we aimed to offer a novel software model to be used for a quantitative description of droughts and wet periods to provide an overview of drought intensity and analyzing their severity, frequency, and duration. In addition, we have been able to develop a state-of-the-art bespoke software application, so the users are able to analyze drought based on the regional thresholds. While most of the analysis applications have used programming languages such as R or Python, due to the lack of software libraries in the .NET development environment, we have managed to offer our development environment based on .NET Core and C# programming language. The software application accepts inputs from various file formats or APIs, processes the data, and demonstrates the outcome in different graphs and maps depending on the geographical location of study areas. The outputs are not only can be exported as different formats to be used in big data applications but also might be exposed as web APIs to be used in live applications.&#160;&#160;Keywords: Drought characteristics, SDF Calculator, API, Standardized Drought Indices (SDI)

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The Role of Climate Change and Human Factors in Affecting Runoff and Hydrological Drought Characteristics of a Watershed

10.22541/au.162573875.53609866/v1 ◽

2021 ◽

Author(s):

Tesfaye Belay Senbeta ◽

Renata Romanowicz

Keyword(s):

Climate Change ◽

Human Factors ◽

Dominant Role ◽

Hydrological Drought ◽

Drought Indices ◽

Hydrological Models ◽

Climate Elasticity ◽

Drought Characteristics ◽

Runoff Reduction ◽

Long Term Effect

The main objective of the study is to evaluate the roles of climate change and human factors on runoff, baseflow, and hydrological drought characteristics at a watershed scale. The novelty of the study is to assess separately the cascading, indirect, accumulative effects of climate change and human factors on hydrological drought, i.e. runoff and baseflow. This involved analyzing change points to divide the available hydrometeorological data into a baseline and a perturbed period. We applied two hydrological models, SWAT and HBV-light, and two nonparametric climate elasticity of runoff to identify the contribution of climate change and human factors in influencing runoff and baseflow processes. The hydrological models were used to simulate naturalized runoff and baseflow during the perturbed period. The temporal variation in the characteristics of the baseflow regime is expressed as baseflow index. Drought indices, standardized runoff index and standardized baseflow index were used as hydrological drought indicators. A significant change in runoff reduction in the Kamienna watershed began in 1982, suggesting that human factors play a dominant role in influencing runoff. In addition, we found that an increase in baseflow and a decrease in hydrological drought events in the 2010s are a positive long-term effect of human factors such as construction of dams in the watershed. Finally, analyses of changes in land cover dynamics in the watershed over the past four decades using satellite imagery are used to confirm the presence of human interventions.

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