The impact of spectral nudging on cloud simulation with a regional atmospheric model

The impact of spectral nudging on cloud simulation with a regional atmospheric model was examined. Simulated cloudiness of the Regional Model ( REMO) and the Spectrally Nudged REMO ( SN-REMO) were intercompared and evaluated with satellite-derived cloudiness from the International Satellite Cloud Climatology Project ( ISCCP). In general, the additional spectral nudging does not affect the mean cloud simulation. However, for particular weather regimes the introduction of spectral nudging causes notable differences in cloud simulation. Two weather conditions for these large differences in cloud simulation were derived: 1) change of the general circulation patterns, or 2) strong anticyclonic circulation within the model domain. Case studies of these weather situations indicated a better agreement of simulated and satellite-derived cloudiness when spectral nudging has been applied to the regional model.