An attempt is made to connect the moisture present above the boundary layer and its association with the cloud development and boundary layer turbulence using Large Eddy Simulation (LES) and aircraft observations. The dry boundary layer (BL) with shallow clouds observed during Cloud-Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over the arid Indian peninsula is investigated in this study. The constant altitude aircraft observations at different elevations are used to verify LES derived fluxes and variances. LES simulations with the drier conditions above BL resulted in deeper, warmer and drier BL with an enhanced boundary layer turbulent kinetic energy. A dynamic feedback from dry air intrusion into the BL resulted in energetic BL eddies in the dry conditions and a doubling of moisture exchange coefficients. The liquid water content in cloud updrafts rather than in downdrafts were depleted significantly in dry conditions. LES sensitivity indicates that the middle atmospheric water vapor alone could influence the shallow to deep cumulus cloud transitions in the monsoon regime in a dramatic way, by changing the population of cumulus, congestus or deep cumulus clouds. A 30% drying above the BL could drastically reduce the liquid water path and cloud albedo by 10–15%.

使用大涡模拟（LES）和飞机观测，试图将边界层上方的水分及其与云的发展和边界层湍流的联系联系起来。本研究研究了在干旱的印度半岛上进行的气溶胶相互作用和降水增强实验（CAIPEEX）期间观察到的浅云干边界层（BL）。使用恒定高度的飞机在不同高度的观测值来验证LES得出的通量和方差。在BL以上的较干燥条件下进行的LES模拟导致BL较深，较暖和较干燥，且边界层的湍动能增强。来自干燥空气侵入BL的动态反馈导致在干燥条件下充满活力的BL涡流和水分交换系数加倍。在干燥条件下，云上升气流中而不是下降气流中的液态水含量显着减少。LES敏感性表明，仅中层大气水蒸气就能通过改变积云，充血云或深积云的数量，以戏剧性的方式影响季风状态下浅云至深云的过渡。在BL上方干燥30％可以大大减少液态水路径和反照云10-15％。