Regional modeling of evapotranspiration using WRF coupled to the high complexity land surface model ACASA
ACASA (Advanced Canopy-Atmosphere-Soil Algorithm) is a complex multilayer land surface model with interactive biophysical, meteorological and full surface hydrological processes that allows microenvironmental variables such as air and surface temperature, wind speed, humidity, and carbon dioxide concentration to vary vertically. Water vapor, carbon dioxide, energy and momentum fluxes between the atmosphere and the land surface are calculated in ACASA through third order closure turbulence equations and complex canopy physiology, such as 10 leaf classes for better light and precipitation interception. It allows counter-gradient transport that low-order turbulence closure models are unable to simulate. Coupling ACASA with the WRF model bridges the gap between in-situ applications and regional climate research. In this paper, we use WRF-ACASA to simulate evapotranspiration over a transect in Northern California ranging from the coastal area to the Sierra Nevada mountain. The results show that the evapotranspiration, surface and soil temperature, and energy fluxes simulated by the WRF-ACASA coupled model agree better with observational datasets than that of the WRF's pre-existing land surface models. As a result, WRF-ACASA is a promising tool to simulate evapotranspiration under future climate conditions.