Numerical modeling of heavy rainfall event over Maderia Island in Portugal-Sensitivity to Microphysics

Abstract

Madeira Island, Portugal, faced an intense heavy rainfall on 20 February 2010 which lost more than 40 lives and caused great damage. This event is recorded as one of the major flash flood events during the past three decades. Keeping this in view, in the present study a series of numerical experiments using the Weather Research Forecasting model and MESO-NH model at very high resolution of 1 km are performed. Lateral and boundary conditions are updated every 6 hours using NCEP FNL data for WRF model and with ECMWF IFS data for MESO-NH model, available at 1 degree and 0.25 degree resolutions, respectively. The WRF model is designed with four nested domains and an inner domain with 1 km resolution centered on the island, which is the area of interest. MESO-NH model is integrated with 3 domains and inner domain at 1 km resolution located over Madeira Island. Both models show that the extreme rainfall event was originated by the effect of orography on the prevailing large scale flow of a conditionally unstable moist air. Experiments for other heavy rainfall events over Madeira show the same mechanism, indicating the capability of high resolution mesoscale models in reproducing this type of events. At higher resolution, convection parameterization schemes are not so important to resolve mesoscale cloud features but microphysics schemes are important. In this aspect we performed a series of sensitivity experiments with different microphysics schemes. Different cloud microphysical properties are examined and discussed. These cloud microphysical parameters are compared with satellite retrievals. Results indicate that the model is sensitive to different microphysics schemes.