Effect of a Cold, Dry Air Event on Convective Boundary Layer Development in a High-altitude Lake, Tibetan Plateau

Few studies have investigated the response of the atmospheric boundary layer to surface energy and weather variations over Tibetan Plateau lakes. Therefore, the multi-source field data, re-analysis data and remote sensing observations were used to investigate the varying patterns and factors influencing the convective boundary layer (CBL) development in the high-altitude Ngoring Lake basin before and after cold, dry air incursion. The results revealed that the CBL thinned over the lake during the daytime (less than 100 m) and markedly thickened at night (400-600 m) prior to the arrival of the cold air. Along with the arrival of the dry, cold air, the potential temperature and specific humidity rapidly dropped, causing the CBL to thicken to 2280 m over the lake and eventually become thicker than the CBL over the land. During the cold, dry air incursion, the sensible heat flux dramatically dropped over the land, but rapidly increased over the lake, which enhanced the thermal instability of the atmosphere and the CBL growth over the lake. Cooling at different heights weakened the potential temperature lapse rate in the lower troposphere. Thus, the increasing sensible heat flux, weak temperature lapse rate and increasing wind shear provided enough power to promote rapid CBL growth over the lake.