Atmospheric Rivers and Cloudburst Events over North-West Himalaya: A Case Study

Atmospheric Rivers (AR) are widely recognised as one of the main drivers of moisture transport globally. In this study the effect of AR is analysed over the North-West Himalayan (NWH) region during a series of extreme rainfall events (ERE) that occurred during $14^{\text {th }}$ to $18^{\text {th }}$ August 2019, over the North West Himalaya region. In this study, INSAT 3D Imager data of rainfall and OLR, GPM IMERG Rainfall data and ERA5 reanalysis data are used to investigate the synoptic scale feature of the event. High resolution WRF simulations resolved interesting physical processes associated with the series of the cloud burst events along with the large integrated vapor transport (IVT) signifying the presence of Atmospheric River (AR). The results show significant influence of AR over the moisture transport in NWH region that caused the ERE. The steep topography is also playing an important role in the genesis of cloudburst. Vertical profile of cloud shows heavy moisture loading in mid-troposphere ($600-700 \mathrm{hPa}$). The vertical wind velocity shows strong ascent as high as (-1 $\mathrm{Pa} / \mathrm{s}$) in some areas. Strong vertical ascent together with weak temperature gradient shows signs of rapid orographic lifting. The WRF-ARW simulation shows underestimation of rainfall rate (40 to $70 \mathrm{~mm} / \mathrm{hr}$). Overall, the results show that the unique characteristics of Atmospheric Rivers over the Indian subcontinent and its interaction with High Mountain Asia (HMA) has caused this series of cloudburst events.