Little is known about the effects of glacier-air interactions on the Himalayan glacier mass balance. Until this knowledge gap is filled, a reliable projection of the future changes in the Himalayan glaciers is hardly possible. Here, we describe the drying effect of the katabatic winds on the up-valley summer monsoon flows by creating favorable conditions for local convergence-induced precipitation to occur near the glacier fronts. We postulate that this retarding effect on the up-valley monsoon flows results in a negative feedback mechanism mediated by glacier-air interactions, in which glacial retreat pushes precipitation upwards as the down-valley katabatic winds weaken, resulting in greater local precipitation and enhanced snow accumulation across the upper parts of the Himalayan glaciers. Our analyses are based on the exclusive data recorded in the Khumbu valley and the Langtang valley in the Nepalese Himalayas. These data revealed higher afternoon precipitation in summer associated with surface wind convergence near the glacier fronts and a sharp decrease in the temperature lapse rate over the glacier surfaces. The principle of the observed phenomena was proven by our high-resolution modeling sensitive experiment, which involved two simulations, one with the present glaciers and the other without. This numerical experiment also supports the proposed negative feedback. Furthermore, we report a low deuterium excess near the glacier fronts, indicating below-cloud re-evaporation facilitated by the local convergence induced by the dry katabatic winds. Our study suggests that current models may overestimate the retreat of Himalayan glaciers because they have completely ignored the glacier-air interactions.

关于冰川-空气相互作用对喜马拉雅冰川质量平衡的影响知之甚少。在填补这一知识空白之前，很难对喜马拉雅冰川的未来变化做出可靠的预测。在这里，我们通过创造有利条件使局部收敛引起的降水发生在冰川前沿附近，来描述卡塔巴特风对上季夏季风的干燥作用。我们假设这种对上季风季风流动的阻滞作用导致了由冰川-空气相互作用介导的负反馈机制，其中，随着下山谷的卡塔巴特风减弱，冰川退缩将降水向上推，从而导致更大的局部降水和雪的增加喜马拉雅冰川上部的沉积物。我们的分析基于尼泊尔喜马拉雅山的昆布河谷和朗塘河谷中记录的独家数据。这些数据揭示了夏季较高的下午降水，这与冰川锋面附近的地表风汇聚以及冰川表面的温度下降速率急剧下降有关。我们的高分辨率建模敏感实验证明了观测现象的原理，该实验涉及两个模拟，一个模拟有当前的冰川，另一个模拟没有。该数值实验也支持所提出的负反馈。此外，我们报告说，冰川前沿附近的氘过量较低，这表明由干燥的方正风引起的局部收敛促进了云层下方的再蒸发。