Evaluation of the relation between the convection and the upper tropospheric humidity: A perspective from Indian Geostationary satellite ‘Kalpana-1’ observations

Abstract

High spatial and temporal resolution measurements from the Indian Geostationary satellite ‘Kalpana-1’ have been utilized to find the relation between the convection and upper tropospheric humidity (UTH). The analysis reveals that the UTH leads deep convection by 2–4 h over Indian landmass, which is attributed to the advection associated with tropical easterly jet rather than the direct overshooting monsoon convection. In contradiction, the UTH lags convection by 2–6 h over nearby oceans, indicating that direct overshooting convection plays a major role in moistening the upper troposphere. A new mechanism is proposed in which, if the UTH leads to deep convection, thick and dense high-altitude clouds form that can lead to negative feedback to convection through radiative cooling. If UTH lags convection then thin clouds form, thereby can result in positive feedback for convection. However, this feedback to convection is controlled by the presence of the TEJ.