Determination of Desert Soil Apparent Thermal Diffusivity Using a Conduction‐Convection Algorithm

Surface soil temperatures impact land‐atmosphere interactions in desert environments. Soil apparent thermal diffusivity ( k ) is a crucial physical parameter affecting soil temperature. Previous studies using the conduction‐convection algorithm reported k values of desert soils for only a few days. The main objective of this study is to determine the daily and monthly variations of desert k for a range of water contents over a 10 month period. The k values were estimated with a conduction‐convection algorithm using soil temperature measured at the 0.00 m and 0.20 m depths from 1 January to 11 October 2011 at the Tazhong station in the Taklimakan desert of China. Generally, the daily values of k ranged from 1.46  ×  10 −7 m 2   s −1 to 5.88  × 10 −7 m 2   s −1 , and the 10 month average k value was 2.5(±0.8)  ×  10 −7 m 2   s −1 for the 0.00 m to 0.20 m soil layer. The k values varied significantly with soil water content. The apparent convection parameter ( W ) , which is the sum of the vertical gradient of k and apparent water flux density, was also determined. Comparison of the magnitudes of W and k gradients indicated that little water movement occurred during the dry months, some water infiltrated downward during the wet months, and some water moved upwards in response to evaporation following the wet months. These findings confirmed that the conduction‐convection algorithm described the general pattern of soil water movement. The presented daily and monthly values of k can be used as soil parameters when modeling land‐atmosphere interactions in the Taklimakan desert.