Observations and Modeling of Thermally Driven Flows over the Great Salt Lake Desert

The Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program seeks to identify and address gaps in knowledge, modeling, and technology needed to advance weather prediction in areas of complex terrain. The first phase of the field program will occur in September and October 2012 at Dugway Proving Ground in the Great Salt Lake Desert of northwest Utah. Thermally driven flows over this area are generated by basin-and-range topography, the Great Salt Lake (GSL), and spatially varying desert ecosystems such as salt playas, grasslands, and shrublands. This study utilizes operational simulations run at Dugway Proving Ground with a WRF-based forecast system known as 4DWX, developed by the National Center for Atmospheric Research and the Army Test and Evaluation Command. These simulations demonstrate the WRF's ability to generate realistic flows produced by the GSL and complex terrain during periods of quiescent weather, but also shortcomings related to land-surface and boundary layer contrasts between the salt playa and adjoining grasslands and shrublands. For example, the boundary separating the playa of the Great Salt Lake Desert from the surrounding grasslands and shrublands cuts through the middle of the MATERHORN study area, but the WRF model does not capture the contrast in boundary layer structure over these two land surfaces, as suggested by surface automated meteorological stations. Observed surface temperature differences over these land surfaces are greatest in the early morning and afternoon during quiescent periods, and are most pronounced in September. This poster will present climatological analyses of the thermal contrast and circulations over these and surfaces and examine the factors contributing to the errors in the WRF simulations.