| Description |
This dissertation examines the performance of Weather Research and Forecasting (WRF) model near-surface temperature and surface energy balance forecasts over Dugway Proving Ground (DPG) in northwest Utah during the Mountain Terrain Atmospheric Modeling and Observations Program (MATERHORN) field campaigns. This region of complex terrain has two distinct land surfaces, playa and sparsely vegetated desert shrub, which are common in other dryland regions. Operational WRF forecasts show persistent underprediction of the diurnal temperature range due to a nighttime warm bias and a daytime cold bias. The former is especially strong over the desert shrub. The nighttime warm bias can be improved through the utilization of in situ soil moisture observations and by replacing Johansen's 1975 parameterization of soil thermal conductivity in the Noah land surface model with that proposed by McCumber and Pielke in 1981 for silt loam and sandy loam soils. The daytime cold bias extends from the surface to above the top of the planetary boundary layer and is primarily caused by a regional overestimation of near-surface soil-moisture in operational land-surface analyses, which do not currently assimilate in situ soil-moisture observations. Bias correction of the soil-moisture analyses across the Intermountain West using North American Soil Moisture Database observations reduces the daytime cold bias. Utilization of observed soil moisture and the McCumber and Pielke soil thermal conductivity parameterization also improves the surface energy balance forecast over the desert shrub, but degrades it over the playa. Land surface processes unique to the playa are not currently accounted for in the Noah land surface model. Nevertheless, a larger and more accurate temperature gradient develops between the playa and desert shrub that forces a stronger daytime off-playa breeze. However, 10-m wind speed and direction forecasts show limited statistically significant improvement. This dissertation also presents a climatology of episodic dust events across the Intermountain West and locates dust source regions through a dust retrieval algorithm adapted for data from geostationary operational environmental satellites. |
