A discussion about the role of the shortwave schemes on real WRF-ARWsimulations. Two case studies: Cloudless and cloudy sky

Abstract

parameterizations. Differences in these approximations bring about to distinct results for the radiative fluxes, even under the same atmospheric conditions. 5 Since the transfer of solar and terrestrial radiation represents the primordial physical process that shapes the atmospheric circulation, those deviations must have and impact on the numerical weather prediction (NWP) model performance. In this paper, an analysis of the role of the shortwave 10 schemes on the Weather Research and Forecasting (WRFARW) model is presented. The study compares the effect of four parameterizations (Dudhia, New Goddard, CAM and RRTMG) in two cases: i) cloudless and ii) cloudy sky situations for a domain defined over Catalonia (northeast of the 15 Iberian Peninsula). We analyze the direct and the indirect feedback between the dynamical aspects and the physical parameterizations driven by changes on the radiative transfer equation computation. The cumulative effect of those variations are studied through three simulation windows: current 20 day (0-23 h), day-ahead (24-47 h) and two days ahead (48-71 h). These analyses are focused on several NWP model fields. From the most directly related to the shortwave schemes such as the global horizontal irradiance or the heating rate profile, 25 to apparently secondary outcomes such as the wind speed or the cloud composition among others. The observed differences between model runs using different solar parameterizations increase with the simulation horizon, being more important in the cloudy scenario than in the cloudless sky.