COMPARISON OF CLOUD MICROPHYSICS SCHEMES IN WRF MODEL FOR SIMULATING MESOSCALE CONVECTIVE SYSTEMS OVER WEST AFRICA

Abstract

This research work evaluated the performances of five cloud microphysics schemes commonly used in Weather Research and Forecasting (WRF) model for simulating mesoscale convective systems occurrences over West Africa. Advanced Research WRF (ARW) dynamical core was used for simulations of each of the five schemes for the whole of September, 2012. The ERA-Interim reanalysis data was used to provide the initial and boundary conditions of the model setup. The Brightness Temperature (BT) and Tropical Rainfall Measurement Mission (TRMM) were used as satellites imageries. 5th - 9th September and 15th - 19th September, 2012 were chosen as case 1 and 2 respectively. The performance evaluation of the BT with the simulated Outgoing Longwave Radiation (OLR) and TRMM with the simulated rain rate were carried out using five microphysics schemes: Lin Purdue, WSM6, Thompson, Morrison DM and WDM5. The results for case 1 (BT with OLR) shows that WSM6 scheme has successfully simulated good spatial features of the model OLR with the highest Coefficient of Efficiency (COE) of -19.730 and least Root Mean Square Error (RMSE) of 38.442 Wm-2, followed by Morrison DM. Similarly, case 2 results presented WSM6 as the best performed scheme with the highest COE of -9.781, least RMSE of 34.969 Wm-2 and mean bias (MB) of -47.425 Wm-2. Furthermore, Case 1 (TRMM with Rain rate) showed WSM6 as the best performed scheme with the least MB of 0.100 mmh-1, least RMSE of 0.114 mmh-1, highest correlation coefficient (r) of 0.937 and COE of -0665. In Case 2 (TRMM with Rain rate), WSM6 again performed very well with the least MB of 0.103 mmh-1, least RMSE of 0.110 mmh-1 as well as the highest r and COE of 0.850 and -0.776 respectively. Thus, WSM6 is the overall best performed scheme, although the model has failed to explain more of the variability in the observations than their mean due to the negative values of COE.