Land surface reflectance, emissivity and temperature from MODIS middle and thermal infrared data

The following paper presents a method to retrieve surface reflectance, emissivity and temperature in the middle infrared (3–5 μm) and thermal infrared (8–12 μm). It is applied to Moderate Resolution Imaging Spectroradiometer (MODIS) data acquired over Southern Africa during the August to October 2000 period. This method relies first on atmospheric correction of the middle-thermal infrared radiances which uses National Center for Environmental Prediction (NCEP) humidity, pressure and temperature profiles and second on constructing and using a database of night emissivities ratio (Temperature Independent Spectral Indices of Emissivity, TISIE). The middle infrared reflectances (3–5 μm) are then derived from day-time measurements and mean TISIE values. By hemispheric integration (over a 16-day period), they lead to middle infrared directional emissivity which, combined with TISIE again, leads to thermal infrared emissivity and surface temperature. The reflectance accuracies are assessed by looking at targets of known reflectance (water and sun-glint). The emissivities in the thermal infrared are assessed by checking the spectral invariance of the derived surface temperature in the 3–5- and 8–12-μm region. Other consistency checks are performed leading to the conclusion that the reflectance, emissivity and surface temperature are derived within ±0.015, ±0.01 and ±1 K, respectively. Finally, a direct application of the MODIS middle infrared surface reflectances to the fire detection problem is developed and the results compared to the Landsat 7 high spatial resolution data.