Life Cycle of Deep Cloud Systems of Indian Summer Monsoon using High Temporal Resolution Satellite Data

Abstract

Life cycle characteristics of deep cloud systems (CSs) formed over India and the surrounding oceans during the summer monsoon season are reported using half-hourly geostationary satellite data. An automated cloud tracking algorithm based on the area overlap method is used. We show that the larger CSs tend to live longer and grow deeper, with some convective towers growing deeper than the tropopause. The CSs over Central India are shorter-lived than those over the Bay of Bengal. Interestingly, they have similar sizes as the peak growth rate of the former is about twice that of the latter, suggesting stronger updrafts in the continental systems. In June and September, CSs formations predominately occur over the orographic features, whereas in July-August, it is associated with the monsoon trough. CSs show a tendency to propagate upwind of the lower tropospheric winds. Merging contributes significantly to the growth and longevity of CSs. This suggests that large and long-lived CSs are formed when the environment can trigger and sustain multiple CSs in close vicinity. The peak in the CS size occurs, around halfway through its lifetime, chronologized by systematic merging and splitting events, i.e., CSs normally have symmetrical growth and decay phases. Whereas the minimum mean cloud-top temperature of CS occurs during the second quarter. This is in consensus with the vertical build-up of convective towers followed by horizontal growth via anvil spreading.