The variation in the precipitation phase in polar regions represents an important indicator of climate change and variability.We studied the precipitation phase at the Great Wall Station and Antarctic Peninsula (AP) region,based on daily precipitation,synoptic records and ERA-Interim data during the austral summers of 1985-2014.Overall,there was no trend in the total precipitation amount or days,but the phase of summer precipitation (rainfall days versus snowfall days)showed opposite trends before and after 2001 at the AP.The total summer rain days/snow days increased/decreased during 1985-2001 and significantly decreased at a rate of-14.13 d (10 yr)-1hncreased at a rate of 14.31 d (10 yr)-1 during 2001-2014,agreeing well with corresponding variations in the surface air temperature.Further,we found that the longitudinal location of the Amundsen Sea low (ASL) should account for the change in the precipitation phase since 2001,as it has shown a westward drift after 2001 [-41.1° (10 yr)-1],leading to stronger cold southerly winds,colder water vapor flux,and more snow over the AP region during summertime.This study points out a supplementary factor for the climate variation on the AP.