Spatiotemporal Analysis And Impacts Assessment Of Agricultural Drought Based On Different Standardized Indices

Drought has been a significant resulted from shortage in precipitation and soil moisture.China is the third largest country in area in the world and has been frequently experienced drought.Recently,increasing temperature,less in rainfall days in summer season caused the different climate regions and geographical suffered by drought.Then the decreasing of storage water in soil layers led to shortage in soil water content.Since the increasing population and economic facilities in China,so the food demand is a major subject.Hence,it is vital to analyze drought considering the decreasing precipitation and soil moisture which influenced to agricultural production is a must.This study aims to assess the variation in precipitation and soil moisture in different climate regions over China,investigate the trends in drought by applying the Standardized Precipitation Index(SPI)and Standardized Soil Moisture Index for 4 timescales – from 1 month to 12 months.The model grid based-datasets that corresponds to meteorological stations distributed in China were obtained from CLDAS-V1.0 and ERA-Interim reanalysis.Observed and model-based data were compared for reference period(2008-2016)in order to examine the reliability of model.Later,modified Mann-Kendall trend test was applied on the SPI and SSI at different timescales for the entire period(1986-2016).The trends were also detected by Theil-Sen and linear regression for comparing with Mann-Kendall trend test over study areas.Afterwards,the correlation assessment analysis was used to investigate the correlation coefficient between meteorological drought(SPI)and agricultural drought(SSI).The results showed that:(1)In short,a persistent increasing drought trend was detected for partial of China such as central China.However,SSI indicated less drought events than SPI,which implied that a low precipitation condition(meteorological drought)may not absolutely lead to a low soil moisture condition(agricultural drought).(2)The correlation coefficients are decreasing with increasing time scale for most of the sub-regions and the correlations were poor in sub-region 6(Qinghai-Tibetan Plateau).Additionally,the relationship between SPI-6 and SSI-1 was very important especially in the humid areas during the growing season,which was more closely related to agricultural drought.(3)While the strongest relationship between SPI and SSI appeared at the 1-month timescale(Pearson ‘correlation coefficient being 0.65)in humid areas.Also,the correlations varied in different sub-regions of China.This confirms that the relationship between SPI and SSI can be explained by area properties and climatic conditions.