Zhichang Guo, P. A. Dirmeyer, and R. Koster
Soil moisture is not only a moisture source to the atmosphere, but also plays an important role in modulating land surface energy balance and its exchange with overlying atmosphere. Recent studies show that soil moisture anomaly has the potential to impact on weather and climate through their interactions with the atmosphere. Since soil moisture is a slowly varying land surface state variable, the realistic land surface initialization could contribute to the atmospheric predictability at sub-seasonal to seasonal timescales.
The Global Land-Atmosphere Coupling Experiment (GLACE) provides a unique look at the impacts of soil moisture on precipitation and air temperature simulations, and the degree to which the realistic land surface initialization could contribute to atmospheric predictability. With COLA AGCM, GLACE-1 and GLACE-2 experiments have been conducted for the years of 1982-2006. Analysis of the results shows that the strength of land-atmosphere coupling has interannual variability, and is largely modulated by the soil moisture anomaly. It is also found that the realistic land surface initialization has significant contribution to near-surface air temperature forecast, and moderate contribution to precipitation prediction at sub-seasonal to seasonal timescales.