Seven years of high-resolution measurements of upper tropospheric humidity (UTH) from the Indian Geostationary satellite, Kalpana-1, are used to understand the hydration and dehydration processes during the active and break phases of the Indian summer monsoon (ISM). The active and break phases are identified using the TRMM-3B42 daily rainfall data over the Central Indian region. The most significant and new observation is that the upper troposphere is dry during the active and wet during the break phases of the ISM. Satellite measurements of humidity from Megha-Tropiques SAPHIR and water vapor mixing ratio from Aura microwave limb sounder also show dryness in the upper troposphere during the active and wetness during the break phases of ISM. The analysis illustrates that dehydration dominates during the active and hydration during the break phases. Cloud-aerosol lidar with orthogonal polarization data shows that cirrus (sub-categorized as sub-visible, thin, and thick) occurrence is more during the active phase as compared with the break phase. The dehydration mechanism during the active phase of ISM is attributed to the presence of cirrus. This study provides evidence that the upper troposphere shows dehydration during the active and hydration during the break phase of the ISM, thereby exhibiting intra-seasonal variability in the UTH.

来自印度对地静止卫星Kalpana-1的七年高分辨率对流层上层湿度（UTH）的高分辨率测量用于了解印度夏季风（ISM）活跃和断裂阶段的水合和脱水过程。使用TRMM-3B42在印度中部地区的每日降雨数据来确定活动和中断阶段。最重要和最新的观察结果是，对流层上层在ISM的活跃期是干的，而在ISM的破裂期是湿的。卫星测量的Megha-Tropiques SAPHIR的湿度和Aura微波肢体测深仪的水蒸气混合比也显示了对流层上部在活动期间的干燥和ISM破裂阶段的潮湿。分析表明，在活性过程中，脱水占主导地位，在断裂阶段则占主导地位。具有正交极化数据的云气溶胶激光雷达显示，与中断阶段相比，活动阶段期间卷云（亚分类为次可见，稀薄和浓密）发生更多。ISM活跃阶段的脱水机制归因于卷云的存在。这项研究提供了证据，即对流层上部在ISM的活动期显示脱水，而在ISM断裂期显示水合作用，从而在UTH内表现出季节内变化。