A study on some dynamical aspects of Uttarakhand heavy rainfall events

Abstract

In recent years, heavy rainfall events have been increasing over the Uttarakhand region. Improvement in the prediction of such events crucially dependent on the inclusion of the physical & dynamical processes responsible for such events, in the NWP model. This again, in turn depends on the understanding of such processes.  In this study an attempt has been made to understand parts of these processes and some of the dynamical aspects of these heavy rainfall events. For this different important derived NWP products, viz., differential vorticity advection (DVA), differential thermal advection (DTA), Differential moisture advection (DMA), Precipitable water (PW), non-dimensional stability index (NDSI) have been computed using ECMWF high-resolution gridded reanalysis data sets.  Heavy rainfall events are defined using IMD high resolution gridded daily rainfall data set. Preliminary analysis revealed that there was a steady increase in DVA, decrease in DTA, increase in PW and decrease in DMA before the heavy rainfall event. An enhanced DVA results in an enhancement in LLC, a decrease in DTA along with a decrease in DMA results in an enhancement of lapse rate. Combined effect of these results in the increase in the low-level convergence at Uttarakhand region along with the rising motion are the major dynamical processes resulted in the heavy rainfall event.