Study of vegetation effects on land-atmospheric interaction using the Weather Research and Forecasting model and MODIS data

Land-atmospheric interactions have been an important issue in weather and climate modeling. Evapotranspiration (ET) is a major feedback from the land surface to the atmosphere and we analyze land surface processes simulated from the Noah (National Centers for Environmental Prediction - Oregon State University - Air Force - National Weather Service Office of Hydrology) Land Surface Model (Noah LSM) coupled with a generic mesoscale model in the Weather Research and Forecasting (WRF) framework. The International H2O project (IHOP) area is the study domain chosen due to the availability of ground observations. Soil moisture and skin surface temperature (TSK) initializations are tested for the model improvement through the comparison to the ground observation data from the 9 Integrated Surface Flux Facilities (ISFF) over the IHOP area. Three days are selected during the study period - DRY1, WET, and DRY2. The relationship between TSK and Normalized Difference Vegetation Indices (NDVI) is assessed to investigate biophysical effects on ET and the model sensitivity to different model initialization. This study indicates that the soil moisture initialization improves soil moisture simulations but causes overestimations of ET in vegetated areas. We further test the parameterization of vegetation fraction derived from daily or semi-monthly Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI to improve the model sensitivity to soil moisture variations. In addition, we evaluate the applicability of vegetation water content which is not involved in the surface flux algorithm but substantially influential on ET.