Impact of Initial Soil Wetness on Seasonal Atmospheric Prediction

Abstract

This study investigates the importance of initial soil wetness in seasonal predictions with dynamical models. Two experiments are performed, each consisting of two ensembles of global climate model integrations initialized from early June observed atmospheric states. In each experiment the only difference between the two ensembles is that they are initialized with a different soil wetness. In the first experiment both ensembles are initialized from 1988 observed atmospheric states and use observed 1988 SST; one ensemble is initialized with seasonally varying climatological soil wetness, and the other is initialized with proxy 1988 soil wetness derived from the European Centre for Medium-Range Weather Forecasts analysis–forecast system. In the second experiment the two ensembles are initialized from observed atmospheric states and use observed SST for five different years, and each ensemble is initialized with a different climatological soil wetness. After initialization, a coupled atmosphere–bios... Abstract This study investigates the importance of initial soil wetness in seasonal predictions with dynamical models. Two experiments are performed, each consisting of two ensembles of global climate model integrations initialized from early June observed atmospheric states. In each experiment the only difference between the two ensembles is that they are initialized with a different soil wetness. In the first experiment both ensembles are initialized from 1988 observed atmospheric states and use observed 1988 SST; one ensemble is initialized with seasonally varying climatological soil wetness, and the other is initialized with proxy 1988 soil wetness derived from the European Centre for Medium-Range Weather Forecasts analysis–forecast system. In the second experiment the two ensembles are initialized from observed atmospheric states and use observed SST for five different years, and each ensemble is initialized with a different climatological soil wetness. After initialization, a coupled atmosphere–bios...