Role of Intra-Seasonal Variability in the Indian Summer Monsoon on the Hydration and Dehydration of the Upper Troposphere

Abstract

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.