Providing Realistic Vegetation Phenological Description for Regional Climate Simulations

A climate version of the Regional Atmospheric Modeling System (ClimRAMS) is used to simulate vegetation-atmosphere interactions in the Great Plains and Rocky Mountain regions of the United States. The NDVI is assumed to provide a remotely sensed measure of the evolution of vegetation phenology and NDVI-derived LAIs are directly assimilated into the ClimRAMS simulations. Two kinds of model integrations have been performed, one with and one without assimilating the observed vegetation distribution. Differences between the model runs are used to highlight model deficiencies and limitations, and to identify areas of possible improvement in the atmospheric model. The results show that seasonal and interannual vegetaion phenological variation strongly influences regional climate patterns via its control of land-surface water and energy exchange. The need to realistically represent vegetation evolution in the regional climate model is thus identified, and is addressed by coupling the CENTURY ecological model with ClimRAMS to account for vegetation growth. The resulting coupled model captures key aspects of weekly, seasonal, and annual feedbacks between the atmopsphere and ecological systems.