Arid-Humid Variations In The Summer Climate And Their Influence Mechanism In Asian Monsoon Margin Of Northwest China During 1960-2010: A Case Study In The Alashan Plateau

In the Asian monsoon margin of Northwest China, the impact factors for variations in the aridity and humidity of the summer climate are complex and unclear. In this study, we selected the Alashan Plateau, located in the mid-latitude arid zone and the Asian monsoon margin of Northwest China, as the study area. Changes in the aridity index K (a proxy for the arid-humid variations in the summer climate of the Alashan Plateau) were calculated for the period 1960-2010 using meteorological data. Relationships among the aridity index K, changes in the intensity of atmospheric circulations, and local precipitation and evaporation in summer are discussed. The results indicated that the arid-humid variations in the summer climate in different regions of Alashan Plateau exhibit significant spatial differences. The summer climate became more humid during 1960-1968 and 1988-1995 and arid in 1996-2010 with different trends, but exhibited asynchronous changes during other periods. Hence, the arid-humid variations in the summer climate exhibited significant spatial differences in the Alashan Plateau. These variations were mainly affected by East Asian summer monsoon in the eastern Alashan Plateau, local precipitation and evaporation in the central and northwestern Alashan Plateau, and atmospheric circulations and evaporation in the southwestern Alashan Plateau. The increase in the monsoon precipitation is not the only factor that affected arid-humid variations in the summer climate over the entire Alashan Plateau, therefore, other non-circulation factors, such as local precipitation and evaporation, should also be considered. The study provides new evidence on how to understand the mechanisms driving global and regional climate change.