Near-real time retrievals of land surface temperature within the MODIS Rapid Response System

The MODIS Rapid Response (RR) System was developed to meet the near real time needs of the applications community. Generally, its products are available online within hours of the satellite overpass. We recently adapted the standard MODIS land surface temperature (LST) split-window algorithm for use in the RR System. To minimize latency, we eliminated the algorithm's dependency on upstream MODIS products. For example, although the standard MODIS LST requires prior retrieval of air temperature and water vapor from the MODIS scene, the RR LST employs a climatological database of atmospheric values based on a 25-year record of NOAA TOVS observations. The standard and RR algorithms also differ in upstream processing, surface emissivity determination, and use of a cloud mask (RR product does not contain one). Comparison of the MODIS RR and standard LST products suggests that biases are generally less than 0.1 K, and root-mean-square differences are less than 1 K despite the presence of some larger outliers. Initial validation with field data suggests the absolute uncertainty of the RR product is below 1 K. The MODIS RR land surface temperature algorithm is a stand-alone computer code. It has no dependencies on external products or toolkits, and is suitable for Direct Broadcast and other processing systems.