Examining the Simulation of Vertically Varying Canopy Microclimate and Turbulence using the ACASA Higher-Order-Closure Soil-Vegetation-Atmosphere Transfer Model and Measurements from the Canopy Horizontal Array Turbulence Study

UCD-ACASA is a higher-order-closure soil-plant-atmosphere transfer model used to simulate canopy turbulence, microclimate, and fluxes of momentum, water vapor, carbon dioxide, and energy. It can be driven at the field scale by above-canopy measurements or at larger scales coupled to a regional model (e.g. WRF). Most past work has focused on top-of-the-canopy fluxes. Here we compare the model's simulation of vertically-varying within-canopy microclimate in a walnut orchard with an extensive set of vertical profile measurements taken during the Canopy Horizontal Array Turbulence Study. Vertical profiles of within- and above-canopy air temperature, humidity, wind speed, turbulence statistics, and fluxes are examined under different atmospheric stability conditions and both before and after leaf-out.