Regional Differences And Causes Analysis Of The Response Of Drought To Climate Change Over China

Using meteorological observation data at weather sites in China during 1960-2012, the characteristics of drought duration in China was analyzed based on SPEI (Standardized Precipitation Evapotranspiration Index) and Penman-Monteith equation. The variability and its causes of dryness/wetness conditions and ET0(Reference evapotranspiration) are quantitatively calculated by several sensitivity experiments. The main conclusions are as follows:(1) There are obvious regional differences in the trend of various types of drought duration in China. Drought events in the Northwestern River Basin (NWRB)reduced, while the mild drought events in the Yellow River Basin (YRB) showed an increasing trend. In addition,the duration of severe drought in the Songhua River Basin (SHRB),southern Liaohe River Basin (LRB), central Changjiang River Basin (CJRB) and Southwest River Basin (SWRB) increased, while the duration of severe drought in the Haihe River Basin (HRB) and the Huaihe River Basin (HaRB)decreased significantly. The changes of drought duration in different regions are the result of common effects of precipitation and ET0.(2) Seasonal and annual ET0 all show decreasing trend over China, especially in summer. The decrease of wind speed is the main reason for the trend of annual average reference evapotranspiration in whole China, which is mainly concentrate in the north of CJRB, whereas in the south of CJRB, net radiation is the main cause. In seasonal scale, WND is the major contributor of (except for summer with RN) ET0 decreases.(3) During the past 52 years,the annual average SPEI trends exhibit "+-+"spatial distribution from Northwestern to Southeastern China. The seasonal variation of dry and wet trend show large difference. Results show that precipitation is the dominant factor of annual dryness/wetness change over YRB, CJRB and its south basin, while reference evapotranpiration affect mainly in the northern basin. In seasonal scale, although the dominant role of precipitation is more obvious, ET0 exceeds that of precipitation in summer. Therefore, the influence of ET0 on local dryness/wetness changes is worth noting.