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Journal of Materials Science: Materials in Electronics
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Iranian Water Researches Journal
Assessing the Impact of Climate Change on the Drought Status in Tabriz Station During Future Periods Using LARS-WG

 submission: 21/10/2019 | acception: 21/12/2019 | publication: 07/09/2020


khadijeh Javan1*, mahdi Erfanian2

1-Urmia university،kh.javan@urmia.ac.ir

2-Urmia university،erfanian.ma@gmail.com



Abstract Drought is one of the most widespread and devastating natural hazards, which is compounded by climate change. Indicators are widely used to provide an overview of drought conditions. In this study, the impacts of climate change on drought status in Tabriz station during future periods were investigated using Deciles Index (DI) and the Standardized Precipitation Index (SPI). At first, the daily output data of HadGEM۲ model under RCP۲.۶, RCP۴.۵ and RCP۸.۵ scenarios were downscaled by LARS-WG version ۶ and the ability of the model was confirmed to simulate the past climate (۱۹۸۷-۲۰۱۶) in Tabriz, then the precipitation was simulated for Future periods of ۲۰۲۱-۲۰۴۰, ۲۰۴۱-۲۰۶۰, and ۲۰۶۱-۲۰۸۰. Using simulated precipitation data, drought status in Tabriz was assessed using two drought indices on an annual scale. The results show that in most of the studied years, the number of droughts decreased in all three future periods compared to the base period and the number of wet years increased. The results of drought monitoring and its prediction for future periods can be used in natural resource management as well as water resource management planning. Introduction: In recent years, weather and climate researchers have identified climate change as the most important concern due to increased greenhouse gas emissions and global warming. Drought is one of the most important and most common disasters affected by climate change that is slowly and progressively causing environmental, agricultural and economic damage in both dry and humid climates around the world (Li et al., ۲۰۱۳). Since drought affects different segments of society such as water resources, agriculture, industry, economy, health, etc., monitoring and evaluation of this factor in the present and in the future in order to provide proper planning in different parts of society is necessary. Climatologists are currently simulating climate variables using general atmospheric circulation models (Barrow and Yu, ۲۰۰۵). The main purpose of these models is to calculate three-dimensional climate indices in specific grids. The outputs of these models have low spatial accuracy. Therefore, if their output directly enters hydrological models, it increases uncertainty. Downscaling methods are used today to increase the spatial accuracy of these data. Downscaling methods are divided into two categories: dynamic and statistical (Beecham et al., ۲۰۱۴). Statistical methods are commonly used in climatic studies. In this study, the output of HadGEM۲ model under RCP۲.۶, RCP۴.۵ and RCP۸.۵ scenarios are downscaled by statistical method and LARS-WG model. The daily climatic variables such as minimum temperature, maximum temperature, precipitation and sunshine for Tabriz station are produced for the next three periods of ۲۰۲۱-۲۰۴۰, ۲۰۴۱-۲۰۶۰ and ۲۰۶۱-۲۰۸۰. Then, using simulated rainfall data, the drought status of Tabriz station is evaluated using two decile indices (DI) and Standardized precipitation index (SPI). Methods: The study area in this research is Tabriz Synoptic Station which is geographically located in northwest of Iran. The data used include observed and simulated data. The observed data are for ۱۹۸۷- ۲۰۱۶. The simulated data include HadGEM۲ model that is downscaled by LARS-WG under RCP۲.۶, RCP۴.۵ and RCP۸.۵ scenarios. LARS-WG is one of the most popular models for generating stochastic data and is used to produce daily minimum and maximum temperatures, precipitation and radiation for present and future climatic conditions. This model is more applicable than others due to repeated computation, less data input, simplicity and performance (Kilsby et al., ۲۰۰۷). Results: After primary data analysis, daily precipitation series were generated and then LARS-WG was implemented. After analyzing the input data and the initial statistical studies, the base state scenarios were implemented for the observed data and the precipitation data were simulated. Model validation based on observed and simulated precipitation values shows high agreement of the model with the observed data. Then precipitation data were tested for normality of distribution. The results show that the precipitation data follows the normal distribution. After ensuring the model's capability to simulate precipitation data series for Tabriz station, this model was run for three periods ۲۰۲۱-۲۰۴۰, ۲۰۶۰-۲۰۴۱ and ۲۰۶۱-۲۰۸۰ using HadGEM۲ output under RCP۲.۶, RCP۴.۵ and RCP۸.۵. Then annual drought was calculated using SPI and DI indices. Investigation of drought status using SPI index shows that in most of the years, the number of droughts decreased compared to the base period (۱۹۸۷-۲۰۱۶) and the number of wet periods increased. Evaluation of the DI index also shows that in all future periods the number of extreme, severe and mild droughts decreased compared to the base period, but the number of moderate droughts increased. According to this index, the percentage of normal years will increase significantly in all three future periods, but the percentage of wet years will show a significant decrease.


Climate Change  Drought  HadGEM۲  LARS WG  Tabriz. 

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