Observed and Modeled Properties of the Atmospheric Boundary Layer During SGP97

During the Southern Great Plains 1997 (SGP97) Hydrology Experiment, a tethersonde system was deployed at DOE's Atmospheric Radiation Measurement/Cloud and Radiation Testbed (ARM/CART) Central Facility. Additional measurements included several surface flux stations at the Central Facility and radiosondes at the ARM/CART Central and Boundary Facilities. Combined, these data support an examination of boundary layer structure and the process of entrainment during the morning transition. Based on surface flux data, we find an entrainment parameter consistent with that obtained in previous studies. We also find that the entrainment parameter exhibits a considerable diurnal cycle, presumably related to the interplay between buoyant and shear production of turbulent kinetic energy (TKE) near the entrainment zone. The observed boundary layer structure and entrainment parameters will be compared to model results obtained using MM5 with a 1.5-order turbulence closure scheme and a watershed-scale land surface parameterization (TOPLATS).