Dynamics and thermodynamics of extreme rainfall event over different subregions of Himachal Pradesh during 8–10 July, 2023
摘要
The summer monsoon of 2023 witnessed catastrophic rainfall occurrences to the mountainous regions of Himachal Pradesh (HP), prompting an investigation into the underlying cause of the anomalous rainfall observed from 8 to 10 July, 2023. This study analyses the spatial and temporal characteristics of the extreme rainfall by utilising half hourly GPM_IMERG data (0.1° × 0.1°) and ERA 5 data (0.25° × 0.25°). Dynamic and thermodynamic conditions across four subregions, representing different mountainous elevations were analysed during the extreme rainfall event. Four subregions were identified based on the intensity of maximum rainfall exceeding 50 mm h− 1. Subregional analysis revealed that rainfall in subregions 1 and 2 was predominantly influenced by low level convergence, whereas subregions 3 and 4 were primarily driven by low level cyclonic vorticity. The timing of maximum vertical motion exhibiting varied lead times, 7 h prior to rainfall in subregions 1 and 2 and 12 to 14 h in subregions 3 and 4. These findings suggest a longer atmospheric response time in elevated regions compared to lower regions. While dynamic forcing played a dominant role in driving extreme rainfall in higher elevations, a combination of dynamic and thermodynamic processes governed the intense rainfall in lower subregions.