Remote estimation of thermal inertia and soil heat flux for bare soil

Abstract

A method is presented which allows thermal inertia (the soil heat capacity times the square root of the soil thermal diffusivity, C h D h ), to be estimated remotely from micrometeorological observations. The method uses the drop in surface temperature, T s, between sunset and sunrise, and the average night-time net radiation during that period, for clear, still nights. A Fourier series analysis was applied to analyse the time series of T s. The Fourier series constants, together with the remote estimate of thermal inertia, were used in an analytical expression to calculate diurnal estimates of the soil heat flux, G. These remote estimates of C h D h and G compared well with values derived from in situ sensors. The remote and in situ estimates of C h D h both correlated well with topsoil moisture content. This method potentially allows area-average estimates of thermal inertia and soil heat flux to be derived from remote sensing, e.g. METEOSAT Second Generation, where the area is determined by the sensor’s height and viewing angle.