Atmospheric turbulence induced errors on measurements of surface temperature from space

Abstract

Atmospheric turbulence in both surface (SBL) and planetary (PBL) boundary-layers induce temporal fluctuations of surface temperature (Ts), with potentially important resulting errors on instantaneous satellite measurements in the thermal infrared (TIR). Several experimental studies have been performed over different surfaces (pine forest, maize, bare soil) using TIR cameras, either ground based or helicopter borne, designed to evaluate (i) how the spatial resolution operates a smoothing of the temporal fluctuations of the surface temperature measurements from space, and (ii) the resulting uncertainty on these measurements. Additionally, a simulation of instantaneous surface temperatures of a maritime pine stand, performed using a Large Eddy Simulation (LES) airflow model coupled with a canopy model, is presented for comparison. The results confirm that the impact of the SBL turbulence rapidly vanishes when spatial resolution decreases (i.e., pixel size increases) in the range of 50 to 100m, while Ts fluctuations induced by the low frequency PBL turbulence remain. For these resolutions, the resulting uncertainty on Ts lies within a ±1°C interval. The implications for designing the specifications of future high spatial resolution TIR missions, in particular NeDT and revisit, are discussed.