Vegetation transpiration is an effective and substantive way to transport water vapor from water stored in soil and plays an important role in weather and climate, and canopy resistance formulation can significantly modulate surface evaporation. Hence we investigated the impact of using a photosynthesis-based canopy resistance approach (the Ball-Berry formulation in the GEM model) along with new MODIS-based land products on the simulation of vegetation transpiration. Our analysis of observations shows that the minimum canopy resistance (Rcmin), which is assumed to be constant in the traditional Jarvis-approach, varies significantly with time. The Ball-Berry formulation responds to environmental conditions differently than Jarvis scheme. Based on evaluation of model results against field data from IHOP_2002, Ameriflux, and Okmesonet, the Ball-Berry scheme usually produces better latent heat flux, soil moisture, and soil temperature.

Impacts of new satellite data from MODIS such as land-use and time-varying vegetation fields are studied using offline-HRLDAS (High Resolution Land Data Assimilation System) and coupled WRF/Noah simulations modeling at high resolution runs with two nested domains with 12km and 4 km resolution over Southern Great Plains of US. These results will be discussed at the meeting.