Satellite sensed summer monsoon torrential rain events characteristics along the Himalayan regions of North India and their dynamics

Abstract

In the past three decades, the total number of extreme rainfall events over northern India has increased, which majorly caused flooding and landslides over the Himalayan foothills and the north Indian region. Some extreme events are reported as torrential rainfall or cloudburst events; others are linked with large-scale weather systems. In this article, we identified extreme precipitation events over northern India during the summer monsoon season using satellite-sensed high-resolution precipitation. Historically noted cloudbursts were selected from these extreme events to study the mechanisms behind their development. The cloudburst events were classified into five primary classes, C1, C2, C3, C4, and C5, based on the large-scale weather systems in the lower, middle, and upper troposphere. A detailed understanding of each class of cloudburst has been carried out to know the precursors for their formation, the dynamical mechanism involved in their development, and the thermodynamic features responsible for causing extreme rainfall. It is found that cloudburst events of classes C1, C2, and C3 are seen during the active monsoon season. Classes C4 and C5 cloudburst events are linked with the monsoon hiatus/break period. In the active monsoon season, these cloudburst events are associated with lower atmosphere cyclonic circulation over the head Bay of Bengal in class C1, and cyclonic circulation centered over Central India in class C2, and East-West oriented low-pressure conveyor system over central India in class C3. Additionally, thermodynamic analysis of each class revealed that class C1, C2, and C3 cloudbursts were associated with the moist instability of the atmosphere during the cloudburst events, where orographic forcing created potential instability and made them intense and overwhelming.