Study on Convective and Non-Convective Rain of Different Heavy Rainfall Events in the Monsoon Season using WRF-ARW Model

Abstract

In the present study the Advanced Research WRF (ARW) model v3.8.1 have been used to simulate the convective and non-convective rain during 3-5 July 2017, 19-20 July 2017 and 23-24 July 2017, when heavy rain observed in different areas of Bangladesh. The initial and boundary conditions are drawn from the global operational analysis and forecast products of National Center for Environmental Prediction (NCEP) Final reanalysis (FNL) data available at 1o ×1o resolution. The model was configured in nested domain with 18 km and 6 km horizontal grid spacing 100×96 and 103×127 grids in the east-west and north-south directions with 28 vertical levels. In this research 12 Cumulus parameterization (CP) schemes in combination with WDM6 microphysics (MP) scheme has been used to identify the convective and non-convective rain of different heavy rainfall (HR) events. The CP schemes used in this research are Kain-Fritsch (KF), Betts-Miller-Janjic (BMJ), Grell-Freitas (GF), Old simplified Arakawa-Schubert (OSAS), Grell-3 (G3), Tiedtke, Zhang-McFarlane (ZM), Multi-scale KF (MSKF), New SAS, New Tiedtke (NTD), New SAS-HWRF (NSH) and Grell-Devenyi (GD). The model simulated rainfall mainly convective for KF, GF, OSAS, G-3, TD, ZM, NTD, NSH and schemes and mainly non-convective for BMJ, MSKF and NS schemes during all over Bangladesh during 3-5 July 2017. BMJ, MSKF and NS schemes have simulated higher non convective rain (NCR) and all other cumulus parameterization schemes have simulated higher convective rain (CR) all over Bangladesh during 19-20 July 2017. OSAS and NSH schemes have simulated higher convective rain and all other cumulus parameterization schemes have simulated higher non-convective rain all over Bangladesh during 23-24 July 2017. It is also seen that during the two simulation periods (i.e., 3-5 and 23-24 July 2017) the CR is found to decrease continuously and NCR increased during the period and opposite in case of 19-20 July 2017. GF and G-3, GF and MSKF schemes give the better performance for daily and 48 hour prediction respectively on the basis of Threat Score, Equivalent Threat Score and Bias Score during 3-5 July 2017. On the basis of Threat Score, Equitable Threat Score and Bias Score for the prediction of HR KF and MSKF schemes during 19-20 July 2017, TD and KF schemes during 23-24 July 2017 give the better performance.