Exploring the Impacts of Soil Moisture/Temperature Variation on Atmospheric Boundary Layer from a Turbulent Mechanism Perspective

Land surface heterogeneity affects the surface energy and water budgets, as well as the land-atmosphere exchanges of heat, water, momentum, and other constituents. Turbulence plays an important role in the efficiency of mass and energy transfer and mixing in the Atmospheric Boundary Layer (ABL). This study represents an approach to exploring how the observed turbulent characteristics change with changes in soil moisture/temperature and the importance of turbulent representations within the surface and boundary layer using Weather Research and Forecasting (WRF) model coupled with a simple and a complex current land surface model (LSM). Using NCEP FNL Operational Global Analysis data on 1.0x1.0 degree grids prepared operationally every six hours to initialize a series of model runs over Southern Great Plains during summer time, different 24 hours periods diurnal cycle simulation are performed to capture enough realizations of the performance of high resolution LSMs to turbulent fluxes over a large heterogeneous terrain. The half hour averaged energy fluxes, soil temperature, soil moisture, specific humidity, wind speed, and turbulent characteristics are simulated and compared to the measurements collected by Meteorological towers. Good agreements are obtained in comparisons between model simulations and field observations indicating that both simple and complex LSM coupled with WRF can reasonably represent mean characteristics in ABL. A half hour time period from 1500CST to 1530CST with 5 seconds output is analyzed via the turbulent energy spectrum. Vertical soundings observed at weather stations are used as a comparison to the simulations from WRF-LSM to investigate the physical processes involved in the land-atmosphere feedback of water and energy balance. Results indicate that the turbulent energy spectral analysis and vertical distributions of certain quantities, i.e. buoyancy, moisture, and TKE reflect the effects of surface heterogeneity, as the land surface energy partitioning has impacts on the behavior and structure of momentum and scalars within ABL. Most importantly, better understanding of how the observed turbulent characteristics change with changes in landscape properties and how current models simulate these feedbacks are obtained.