Derivation of Land Surface Temperature from MODIS Data Using the General Split Window Technique

Fast Atmospheric Signature Code (FASCODE), a line-by-line radiative transfer programme, was used to simulate Moderate Resolution Imaging Spectroradiometer (MODIS) data at wavelengths 11.03 and 12.02 mm to ascertain how accurately the land surface temperature (LST) can be inferred, by the split window technique (SWT), for a wide range of atmospheric and terrestrial conditions. The approach starts from the Ulivieri algorithm, originally applied to Advanced Very High Resolution Radiometer (AVHRR) channels 4 and 5. This algorithm proved to be very accurate compared to several others and takes into account the atmospheric effects, in particular the water vapour column (WVC) amount and a non-unitary surface emissivity. Extended simulations allowed the determination of new coefficients of this algorithm appropriate to MODIS bands 31 and 32, using different atmospheric conditions. The algorithm was also improved by removing some of the hypothesis on which its original expression was based. This led to the addition of a new corrective term that took into account the interdependence between water vapour and non-unitary emissivity values and their effects on the retrieved surface temperature. The LST products were validated within 1K with in situ LSTs in 11 cases.