Characteristics and genesis of precipitation in Panzhihua on the southeast margin of Qinghai-Tibet Plateau

To enhance our comprehension of the precipitation patterns and underlying causes in the complex terrain area of the southeastern edge of the Qinghai Tibet Plateau, the observation data of 72 automatic weather stations in this area and the ERA5 reanalysis data with a resolution of 0.25°×0.25° obtained from the European Center between 2015 and 2020 were utilized to analyze the precipitation characteristics and genesis in Panzhihua. The results indicate that: (1) The precipitation in Panzhihua exhibits a prominent topographic effect, showing a significant decrease from north to south in annual precipitation distribution. The number of precipitation days is one of the main factors for the spatial distribution difference in precipitation. (2) Panzhihua displays obvious nighttime rain features, which shows a unimodal pattern, with the peak precipitation occurring at 03∶00 BT. Panzhihua is located in a dry and hot valley area, and thus experiences low daytime humidity and high nighttime humidity. The saturated atmosphere at night is more likely to lead to condensation, resulting in precipitation. The diurnal variation of humidity is one of the reasons why nighttime rain prevails in Panzhihua. (3) Panzhihua has distinct dry and wet seasons, with June to October being the wet season, November to May of the following year being the dry season, and June and October being the transition period between dry and wet. In June, the southwest monsoon breaks out in the Bay of Bengal, and the rainy season begins in Panzhihua, gradually the dry season finishes. In October, the dry southern branch of the plateau's westerly airflow strengthens, and the rainy season tends to end and the dry season begins.