Sensitivity of Near-Surface Temperature Forecasts to Soil Properties over a Sparsely Vegetated Dryland Region

• Published in: Journal of applied meteorology and climatology 2014-08, Vol.53 (8), p.1976-1995
• Main Authors: Massey, Jeffrey D., Steenburgh, W. James, Hoch, Sebastian W., Knievel, Jason C.
• Format: Article
• Language: English
• Subjects: Arid zones; Bias; Data assimilation; Desert soils; Forecasting models; Freshwater; Heat conductivity; Heat flux; Heat transfer; Lakes; Land surface models; Loam; Loam soils; Mathematical models; Moisture effects; Nocturnal cooling; Parameterization; Parametrization; Playas; Radiation; Sandy loam; Sandy loam soils; Sandy soils; Satellites; Silt; Silt loam; Silt loam soils; Silts; Soil (material); Soil conductivity; Soil moisture; Soil properties; Soil temperature; Soil texture; Soil types; Soil water; SPECIAL MATERHORN COLLECTION; Surface temperature; Temperature; Thermal conductivity; Vegetation; Weather forecasting
• ISSN: 1558-8424; 1558-8432
• DOI: 10.1175/JAMC-D-13-0362.1

Weather Research and Forecasting Model forecasts over the Great Salt Lake Desert erroneously underpredict nocturnal cooling over the sparsely vegetated silt loam soil area of Dugway Proving Ground in northern Utah, with a mean positive bias error in temperature at 2m AGL of 3.4°C in the early morning [1200 UTC (0500 LST)]. Positive early-morning bias errors also exist in nearby sandy loam soil areas. These biases are related to the improper initialization of soil moisture and parameterization of soil thermal conductivity in silt loam and sandy loam soils. Forecasts of 2-m temperature can be improved by initializing with observed soil moisture 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. Case studies illustrate that this change can dramatically reduce nighttime warm biases in 2-m temperature over silt loamand sandy loam soils, with the greatest improvement during periods of low soil moisture. Predicted ground heat flux, soil thermal conductivity, near-surface radiative fluxes, and low-level thermal profiles also more closely match observations. Similar results are anticipated in other dryland regions with analogous soil types, sparse vegetation, and low soil moisture.