Seasonal drought pattern changes due to climate variability in Afghanistan

Abstract

This study assessed the changes in meteorological droughts severity and its return periods during cropping seasons of Afghanistan for the period 1901-2010. Reconstruction of droughts for the country was conducted using standardized precipitation evapotranspiration index (SPEI). Global precipitation climatology center (GPCC) rainfall and climate research unit (CRU) temperature data both at 0.5º resolutions were used for this purpose. Seasonal droughts return periods were estimated using the values of the SPEI fitted with the best distribution function. Unidirectional trends in climatic variables and SPEI were assessed using modified Mann-Kendal trend test, which has the ability of removing the influence of long-term persistence on trend significance. The study revealed increases in drought severity and frequency in Afghanistan over the study period. Temperature, which increased up to 0.14 º C/decade, is the major factor influencing decreases in the SPEI values at the northwest and southwest of the country during rice and corn growing seasons, while increasing temperature and decreasing rainfall are the cause of decrease SPEI during wheat growing season. The study concluded that temperature plays a more significant role in decreasing the SPEI values and therefore, more severe droughts in future due to global warming.