Retrievals of All-Weather Daily Air Temperature Using MODIS and AMSR-E Data

Satellite optical-infrared remote sensing from the Moderate Resolution Imaging Spectroradiometer (MODIS) provides effective air temperature (T-a) retrieval at a spatial resolution of 5 km. However, frequent cloud cover can result in substantial signal loss and remote sensing retrieval error in MODIS T-a. We presented a simple pixel-wise empirical regression method combining synergistic information from MODIS T-a and 37 GHz frequency brightness temperature (T-b) retrievals from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) for estimating surface level T-a under both clear and cloudy sky conditions in the United States for 2006. The instantaneous T-a retrievals showed favorable agreement with in situ air temperature records from 40 AmeriFlux tower sites; mean R-2 correspondence was 86.5 and 82.7 percent, while root mean square errors (RMSE) for the T-a retrievals were 4.58 K and 4.99 K for clear and cloudy sky conditions, respectively. Daily mean T-a was estimated using the instantaneous T-a retrievals from day/night overpasses, and showed favorable agreement with local tower measurements (R-2 = 0.88; RMSE = 3.48 K). The results of this study indicate that the combination of MODIS and AMSR-E sensor data can produce T-a retrievals with reasonable accuracy and relatively fine spatial resolution (similar to 5 km) for clear and cloudy sky conditions.