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 (Ta) 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 R² 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 (R² = 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 (~5 km) for clear and cloudy sky conditions.