Temperature-based and radiance-based validations of the V5 MODIS land surface temperature product

The V5 level 2 land surface temperature (LST) product of the Moderate Resolution Imaging Spectroradiometer (MODIS) was validated over homogeneous rice fields in Valencia, Spain, and the Hainich forest in Germany. For the Valencia site, ground LST measurements were compared with the MOD11_L2 product in the conventional temperature-based (T-based) method. We also applied the alternative radiance-based (R-based) method, with in situ LSTs calculated from brightness temperatures in band 31 through radiative transfer simulations using temperature and water vapor profiles and surface emissivity data. At the Valencia site, profiles were obtained from local radiosonde measurements and from National Centers for Environmental Prediction (NCEP) data. The R-based method was applied at the Hainich site using radiosonde profiles from a nearby sounding station and NCEP profiles. The T-based validation showed average bias ( MODIS minus ground) of -0.3 K, standard deviation of 0.6 K and root mean square error (RMSE) of +/- 0.7 K. For the R-based method, the quality of the atmospheric profiles was assessed through the difference delta(T-31-T-32) between the actual MODIS and the profile-based calculated brightness temperature difference in bands 31 and 32. For the cases where -0.3 K < delta(T-31-T-32) < 0.5 K, the R-based method yielded LST errors with small biases and RMSE = +/- 0.6 K for the two sites. These results show the high accuracy and precision of the MODIS LST product for the two sites studied. The good performance of the R-based method opens the possibility for a more complete validation including heterogeneous surfaces where the T-based method is not feasible.