Surface Sublimation/Evaporation and Condensation/Deposition and Their Links to Westerlies During 2020 on the August-One Glacier, the Semi-Arid Qilian Mountains of Northeast Tibetan Plateau

To identify the links between glacier sublimation/evaporation, condensation/deposition and westerlies, in situ meteorological data and surface roughness lengths during 2020 were collected on a mid-latitude and westerlies-controlled glacier in the northeast TP. Snow or ice sublimation rate was generally believed to be higher during the weather conditions with stronger winds and drier air, while our results showed that the strong westerlies in winter brought the driest and windiest conditions, but did not cause the most sublimation loss due to extremely low surface temperature. The weakening of westerlies intensity and the increased precipitation during summer suppressed the sublimation and evaporation for the low wind speed and high air humidity, and condensation or deposition was more possible during the nighttime of summer together with the radiative cooling on surface and enhancement in atmosphere stability, while annual condensation and deposition were only 1.3 and 14 mm, respectively, which were negligibly small compared to sublimation (115 mm). The westerlies in autumn and spring strengthened sublimation with relatively stronger winds and drier air than summer and higher temperature than winter. Sublimation was more intense in autumn (41 mm/0.4 mm d(-1)) and spring (35 mm/0.4 mm d(-1)) than winter (23 mm/0.2 mm d(-1)) and summer (17 mm/0.2 mm d(-1)). Therefore, westerlies may not be the most crucial driver of glacier sublimation as its effect may be restricted by low surface temperature during a very cold weather.

Automated summary

This study examines the links between glacier sublimation/evaporation, condensation/deposition, and westerlies. The results suggest that while the strong westerlies in winter bring dry and windy conditions, they do not cause the most sublimation loss due to extremely low surface temperature. The weakening of westerlies intensity and increased precipitation during summer suppress sublimation and evaporation, making condensation and deposition more likely. The study concludes that westerlies may not be the most crucial driver of glacier sublimation due to the restriction imposed by low surface temperatures during very cold weather.