Using shortwave radiation to evaluate the HARMONIE-AROME weather model

Abstract

Evaluation of global shortwave irradiance forecasts from the HARMONIE-AROME weather prediction model is presented in this paper. We give examples of how such an evaluation can be used when testing a weather model or reanalysis product. We specifically use the non-dimensional clear sky and variability indices. We have tested seven months of HARMONIE-AROME 40h1.1 output against Danish global irradiance stations and 35 years of the Irish Met éireann reanalysis (MéRA) simulations. MéRA, which is run with HARMONIE-AROME 38h1.2, is shown to have a significantly lower bias than the previously available global horizontal irradiance (GHI) reanalysis data from the ERA-Interim dataset. The Danish HARMONIE-AROME 40h1.1 has a negative bias during the summer months that is not seen in the Irish HARMONIE-AROME 38h1.2. For both model runs, we find a negative bias in the shortwave irradiance forecasts on days with thick clouds. This suggest that the model has too much cloud water in thick clouds.