P61 Numerical simulation of Fog over Indo-Gangetic Plains (IGP), India during CAIPEEX 14-15 and WIFEX15-17 field campaigns using WRF/WRF_Chem models

Prakash, Pithani, Sachin D Ghude, Thara Prabhakaran, P Mukhopadhyay, Phani Murali, Anupam Hazra, Indian Institute of Tropical Meteorology, Anand Karipot, Pune University, R K Jenamani, Indian Meteorological Department, and Rachana Kulkarni, Indian Institute of Tropical Meteorology, India

A series of numerical experiments were carried out with various combinations of physical parameterization schemes to determine the fidelity of the Weather Research and Forecasting (WRF) model (at 2 km resolution) to simulate fog event at Barkachha (in IGP, 25.06 oN, 82.59 oE). These simulations with four Planetary Boundary Layer (PBL) combined with five micro-physics schemes during Cloud Aerosol Interaction and Precipitation Enhancement Experiment Integrated Ground Observational Campaign 2014-15 (CAIPEEX-IGOC) and Winter Fog experiment (WIFEX-2016-17), revealed that the MYNN2.5 PBL scheme with WSM6 microphysics is probably the best combination for simulating Liquid Water Content (LWC) during the fog event This setup was further used for experimental forecast during WIFEX16-17 at IGI Airport, New Delhi. During WIFEX-16-17 we observed 20 fog events. We ran forecast using WRF with IITM-High Resolution GFS (IITM-HIRES-GFS, 12km) and NCMRWF Unified Model (NCUM, 23 km) Initial & Boundary conditions (IC/BC). Out of 20 dense fog events, WRF with IITM-HIRES-GFS and NCUM has forecasted 12 and 19 fog events respectively and false alarm rate for IITM-HIRES-GFS and NCUM is 11(34) and 27 (29) respectively. Model derived LWC variations were intercompared with radiometer observations and depth and duration of fog layer at IGI airport has been evaluated. We also carried out a case study with WRF_Chem to investigate importance of aerosols for visibility forecast during fog event. We found that inclusion of chemistry has improved visibility significantly.