Sensitivity of Near-Surface Temperature Forecasts to Soil Properties over a Dryland Region in Complex Terrain
The silt loam desert warm bias is related to the improper initialization of soil moisture and parameterization of the soil thermal conductivity. 2-m temperature forecasts were improved over silt loam and sandy loam soil textures by initializing with observed soil moisture and by replacing the Johansen (1975) parameterization of soil thermal conductivity in the Noah land-surface model with that proposed by McCumber and Pielke (1981). A case study demonstrates how these changes can reduce a nighttime 2-m temperature warm bias of 4.9°C over silt loam soil textures to 0.8°C. Near-surface temperature improvement is very sensitive to the initialized soil moisture and the greatest improvement occurred during low soil-moisture periods. Predicted ground heat flux and soil thermal conductivity for silt loam soils also more closely matched observations made during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) field campaigns when the McCumber and Pielke (1981) method is used along with observed soil moisture. We anticipate similar results in other dryland regions with analogous soil types, sparse vegetation, and low soil moisture.