Dryness/wetness variations in China during the first 50 years of the 21st century

Abstract. This study investigates future changes of dryness/wetness in China during the first 50 years of the 21st century according to the Standardized Precipitation Index (SPI), which is calculated by monthly precipitation data of ECHAM5/MPI-OM. Three anthropogenic greenhouse gas emission scenarios SRES-A2, SRES-A1B and SRES-B1 have been considered. The frequency of dry/wet periods in ten river basins is counted and the trend is analyzed and detected by a linear regression model and the Mann-Kendall non-parametric test. The results reveal that there is a trend towards drier conditions from Northeast to Southwest China in scenario A2 and a similar spatial distribution pattern in scenario A1B and B1. Areas with a high frequency of drought are detected under three scenarios. In the next half century, the Haihe River basin is expected to show a significant trend towards drier conditions, which pass the 95% confidence level in scenario A2. In the Yellow River basin, the Huaihe River basin, the Yangtze River basin and the Pearl River basin an obvious trend towards wetter conditions has been detected in scenario A1B. The Songhuajiang River basin, the Haihe River basin, the Yellow River basin and the Huaihe River basin show a trend towards wetter conditions, which passed the 90% confidence level in scenario B1. In addition, a decadal variation of dryness/wetness is projected for all the river basins.