Scrutinizing Diurnal Scale Rainfall Variability Over Himachal Pradesh Using High Resolution Satellite-Based GPM-IMERG Product

Abstract

The pattern of monsoon rainfall has been explored at diurnal scale level using the precipitation dataset GPM-3IMERGHH-06 over the state of Himachal Pradesh from 2004 to 2020. The present study identified the spatio-temporal pattern of rainfall peaks and found the trend of rainfall peaks (5% significance level) during different times over selected locations. One-sample student’s t-test has been employed to find the significance of the trend. Intense rainfall peaks (0.7–1 mm/hour) are found at late night (0200 IST to 0230 IST) as well as morning (0600 IST TO 0630 IST) hours over the mountain foot regions and less intense peaks (0.4–0.6 mm/hour) are found during afternoon or evening time (1430 IST to 1700 IST) over southern parts of the state. Late-night peaks of rainfall show a significant increasing trend over the regions Kullu, Mandi, and Sirmaur, while morning peaks of rainfall show a decreasing trend over the same regions. Significant increasing trends have been found over Hamirpur and Mandi during evening hours. The state is characterized by undulating terrain and is prone to extreme rainfall events during the monsoon season. Diurnal pattern of rainfall gives a glimpse into the physical mechanism behind such sudden unexpected events. Trend analysis helps to understand the future risk over different regions which is important for implementing any kind of mitigative actions.