Thunderstorm Dynamics

Lightning and heavy precipitation events in the tropics have significant socio-economic implications for disaster management. Accurate prediction of these meteorological events has remained a challenge despite considerable improvements in Numerical Weather Prediction (NWP) models over the years. With convincing observational evidence of a significant impact of cloud electric field on the raindrop size distribution (RDSD) in the background, we have attempted in this paper to test the model's fidelity in simulating rain events with a strong in-cloud electric environment using the Weather Research and Forecasting (WRF) model. A significant underestimation of observed rain intensity is noted for rain events associated with lightning (Figure 1). It has been observed that the model substantially underestimates the number concentration of larger raindrops relative to the observed RDSD spectrum. A possible roadmap has been discussed to address the observed dry bias in rainfall by incorporating the electrically modified raindrop size distribution (RDSD) parameters into the model physics. Substantial improvement in rain intensity has been observed by incorporating electrically modified RDSD parameters into the model physics. The results presented in this paper strengthen the optimism that with the improved parameterisations of the electrical effect in the physics module of NWP models, the reported dry bias associated with the simulation of heavy precipitation events in the weather/climate models is likely to be minimised and would increase the skill of the models in predicting the intensity of quantitative precipitation.