Analysis of Aridity Trend over Mid-latitude Semi-arid Region Using GLDAS Data

Semi-arid region (annual rainfall totalling 200–600 mm y-1)is one of the most sensitive areas to global climate change. The enhanced warming and aridity trend over mid-latitude semi-arid region are analysed by using by Climate Research Unit monthly temperature data and the assimilation data from Global Land Data Assimilation System (GLDAS). The results show that a particularly large warming trend in semi-arid regions, where the annual, cold season, and warm season mean temperatures increased by 1.13, 1.53, and 0.79°C, respectively. In the same period, the cold season temperatures in semi-arid areas of mid-latitude Europe, Asia, and North America increased by 1.41, 2.42, and 1.50°C, respectively. Such enhanced semi-arid warming (ESAW) lead to increaseevapotranspiration causing dry land even drier. However, there have been distinct differences in the intensification and spatial distribution of aridity trend. The soil water and energy over semi-arid region is continuously reduced from 1980 to 2009.