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Bare soil surface resistance to evaporation by vapor diffusion under semiarid conditions
Author(s) -
Griend Adriaan A.,
Owe Manfred
Publication year - 1994
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/93wr02747
Subject(s) - water content , topsoil , moisture , evaporation , loam , environmental science , wetting , soil water , soil science , water vapor , field capacity , diffusion , materials science , hydrology (agriculture) , geotechnical engineering , composite material , geology , meteorology , thermodynamics , physics
Based on Kohsiek's fast air circulation chamber, a method has been developed to measure the surface resistance to vapor diffusion in a drying topsoil. This resistance is important to estimate evaporation from bare soils using an aerodynamic resistance formulation. Measurements were done for a fine sandy loam during a dry down after artificial wetting. Surface resistance started to increase at a moisture content of 15% by volume in the 1‐cm top layer, which is 50% of its moisture content at field capacity. Calculations of the aerodynamic resistance were corrected for stability and were used to isolate the real surface resistance from the bulk resistance. Resistances could be modeled as a function of the top 1 cm soil moisture and varied between approximately 10 s/m for a wet and several thousand seconds per meter for a dry top layer. The measurements demonstrated a very pronounced diurnal course due to drying of the very top layer during the day and recovery of the moisture profile during nighttime hours.