On the relationship between thermodynamic surface temperature and high-frequency (37 GHz) vertically polarized brightness temperature under semi-aridconditions

A method to estimate surface temperature from high-frequency microwave obse rvations is presented. Microwave brightness temperature is a function of th e emissivity and the physical temperature of the emitting layer, and theref ore possesses a strong physical basis for the estimation of surface tempera ture. Field observations have shown that maximum and minimum daily air temp eratures are strongly related to daytime (1200 h) and night-time (2400 h) s urface temperature, Field measurements of surface temperature are also comp ared to METEOSAT thermal observations. Long-term daily maximum and minimum air temperatures are then used to derive datasets of daytime and night-time surface temperatures. The results indicate that 37 GHz vertical polarizati on brightness temperature provides a reasonable estimate of spatially avera ged surface temperature. This approach could provide a useful tool for clim ate modelling, land surface processes investigations, and other energy bala nce applications by providing consistent and independent long-term estimate s of daily global surface temperature.