Subseasonal impact of extreme Tibetan Plateau snow cover on the local atmosphere in summer

Due to the high elevation and cold climate of the Tibetan Plateau, the western region retains extensive snow cover during the summer, which can exhibit rapid variability over the course of just a few days. This study utilizes numerical experiments to investigate the atmospheric response to extreme Tibetan Plateau snow cover (TPSC) events on a subseasonal timescale during summer. The results indicate that the subseasonal variations in TPSC exert limited impact on nonlocal atmospheric circulation and temperature during this period. Nevertheless, local surface energy and atmospheric temperature exhibit rapid cooling responses to increased snow cover. Specifically, an increase in snow cover over the western Tibetan Plateau leads to a sharp rise in surface albedo, resulting in a reduction in land surface energy and a negative response in the diabatic heating rate from the surface to 350 hPa locally. This negative diabatic heating response subsequently causes a decline in both surface and overlying atmospheric temperatures. The temperature response is confined to the western Tibetan Plateau and extends vertically from the surface to approximately 350 hPa. These extreme TPSC events and their associated atmospheric impacts occur within a two-week timescale.

摘要

青藏高原海拔高, 气候寒冷, 其西部地区在夏季仍有积雪覆盖, 且积雪变化可能在数日内迅速发生. 本文通过数值试验研究了大气对夏季青藏高原极端积雪事件的次季节响应. 结果表明, 尽管极端积雪事件对非局地大气环流及温度的影响有限, 但局地地表能量收支和大气温度对积雪增加表现出快速的冷却响应. 具体而言, 青藏高原西部积雪增加会导致地表反照率迅速上升, 从而减少地表能量输入. 此变化引发了局地地表至350 hPa高度的非绝热加热率的负异常响应, 进而导致地表及上空大气温度下降. 气温响应主要局限于青藏高原西部, 并且从地表垂直延伸至约350 hPa高度. 上述夏季青藏高原极端积雪事件及其大气影响发生在两周时间内.