First, based on tree-ring width and density data, we developed the reconstructions of regional drought and temperature respectively, and analyzed climate combinations of the different areas: (1) The Loess Plateau of Gansu have shown the warm-dry and wet-cold combinations on interannual and decadal scales during warm season, and affected by the East Asian summer monsoon activity during the last 380 years. During the strong monsoon period, the enhanced water vapor transport and increased precipitation can cause the temperature to drop, and vice versa. (2) The Hexi Corridor has the wet-warm and cold-dry combinations during warm season. However, due to the activities of climate system, such as Asian summer monsoon, sea surface temperature, the combination is not stable. (3) Northern Xinjiang also have shown a warm-dry and wet-cold combination on the interannual and decadal scales during the 221 years, however, warm and wet trend was found since the 1980s. Overall, the climate combination of warm season in the arid and semiarid regions of the mid-latitude Asia on the decadal scale is warm-dry and cold-wet.
Second, based on the drought reconstruction, we analyzed the spatial patterns of drought in mid-latitude Asia: (1) The comparison showed that the weak positive correlations were found among the drought series from the monsoonal areas of China, and exhibited strong consistency on the decadal scale. Therefore, the changes in the eastern and western part of the monsoonal region are dominated by the positive phase changes. (2) The drought sequence of the Loess Plateau of Gansu has good correlations with the drought sequence of the Hexi Corridor. The drought reconstructions of Gansu have a good response to extreme events of Northwest China. At the same time, there are also some regional differences between the drought reconstructions of Gansu, which may by affected the interaction of westerlies and Asian summer monsoon. (3) The drought reconstructions of northern Xinjiang show the strong common signals, and there are also some regional differences in different parts of northern Xinjiang. Among them, the most obvious difference is found between the eastern end of the Tien Shan and central-west Tien Shan. The central-west Tien Shan and the Altay Mountains appear wet trend during the recent years, while the eastern end of the Tien Shan appeared to dry trend, and strongly associated with the drought series from the monsoonal areas of China. Thus, the eastern end o...