Assessment of cloud microphysics and cumulus convection schemes to model extreme rainfall events over the Paraiba do Sul River Basin

Abstract

Highly urbanized areas with complex terrains and multiple land uses pose challenges to extreme precipitation forecasts. The present study investigates the performance of several cloud microphysics and cumulus convection parameterizations on a severe rainfall event over the Paraiba do Sul River Basin, an area periodically affected by heavy precipitation. The Weather Research and Forecasting (WRF) model was applied to perform high resolution simulations, and the results were compared against ground observations, weather radar data, and satellite-based precipitation estimates. The simulations tend to underestimate precipitation by an average bias of 55%; however, some experiments showed good fittings in terms of time correlations (over 90%). Overall, the radar vertical profile of reflectivity agrees with observations, where the height of the warm and mixed layers was accurately simulated, despite overpredictions of convective depth (by up to 3 km in regions of intense ascending currents). Typically, WRF was more sensitive to distinct microphysics schemes rather than cloud convection ones. Also, urban areas showed greater precipitation and hydrometeor content in comparison with non-urban ones, even under strong synoptic-scale forcing. The framework was able to reproduce convectively active environments, supporting its application on operational runs over urbanized regions for warning issuing and decision-making.