ASSESSING THE SPRING ATMOSPHERIC CIRCULATION EFFECTS ON GLACIERS IN THE CENTRAL AND SOUTHERN TIBETAN PLATEAU: Insights from observation data and ERA5 reanalysis for surface air temperature, precipitation and precipitation type

Abstract

The Tibetan Plateau consists of several glacier regions that are subject to many near-surface and atmospheric processes. Therefore, it is important to understand their relationships. Spring is typically the transition phase between sublimation and ablation of the glaciers, but the transition variates strongly between locations and elevations. This study assesses the relationship between springtime atmospheric conditions (500 hPa) and potential glacier melt in the southern and central Tibetan Plateau using in situ observations and ERA5 reanalysis data. Near-surface conditions in the glacier regions are assessed using near-surface air temperature (T2m) and precipitation and their combination is used to determine potential glacier melt. An investigation of precipitation types is necessary to examine their contribution to glacier processes (ablation/sublimation). A classification of wind speeds and geopotential height at 500 hPa is conducted using the Self-Organizing Map (SOM) method and it is used as a framework for the elevation analysis and the composite analysis. Results show that atmospheric circulations have larger influences on T2m and precipitation spatially rather than vertically. Additionally, glacier processes are strongly dependent on T2m and therefore indirectly related to atmospheric conditions. Precipitation types differ strongly across elevations and their contribution to glacier melt/accumulation differs largely between locations.