Analysis of Chitwan Wind Storm's Vertical Profile Characteristics through km-Scale Model Simulation and Radio Occultation Data

In the current changing climate scenario, different parts of Nepal face severe weather events like flash floods, hail, heat waves, tornadoes, etc. Some have disastrous impacts on society, infrastructure, and the economy. However, monitoring and predicting those events have been challenging tasks due to the limited meteorological observation infrastructure in the country. In this study we analyzed the vertical profile of the wind storm in Chitwan on 20th May 2022, using various reanalysis, km-scale simulations, and radio occultation data sets. ERA5 and MERRA-2 reanalysis data were used to understand the synoptic-scale phenomenon over the region. We also downscaled ERA5 and MERRA-2 through ICON, and NCEP final reanalysis through WRF, respectively, at km-scale resolution to understand the regional phenomenon. We used the Global Navigation Satellite System-Radio Occultation (GNSS-RO) to figure out how the vertical profile changed during the event since there was no radio-sounding data in the area. ICON at km-scale simulates very high wind gusts over the Chitwan region at about 13 UTC, a similar time range as reported for the wind storm. WRF also shows some signatures but not as prominent as ICON. ERA5 and MERAA-2 completely missed the wind storm. The RO-derived temperature and water vapor profile agreed well with ICON and WRF, with some deviation over the domain. Further vertical profile analysis over Chitwan suggests that during the wind storm, the troposphere gets wetter than earlier, which remains consistent for the next few hours. Specifically, ICON-CLM significantly enhances water vapor in the mid-troposphere (400 hPa).