Using thermal infrared temperature over sparse semi-arid vegetation for sensible heat flux estimation

To estimate sensible heat flux using thermal infra-red temperature T_r over sparse semi-arid vegetation, a knowledge of either the corrective term kB^-1 or the difference between radiometric and aerodynamic surface temperatures T_r-T_o is usually required. Several experimental data sets acquired over various sparse vegetation in semi-arid areas (fallow savannah and millet field of HAPEX-Sahel, grassland and shrubland of MONSOON´ 90) are used to study the experimental behavior of these variables. When considering the extreme variability of kB^-1 and the difficulty in predicting its value, the relationship between T_r and T_o was more thoroughly studied and parameterized using the conceptual two-layer model of Shuttleworth and Wallace (1985)