Evaluating GOES-16 ABI surface brightness temperature observation biases over the central Sierra Nevada of California

Thermal infrared imagery from NOAA's Geostationary Operational Environmental Satellites (GOES) R-series presents an opportunity to observe mountain surface temperatures at high temporal resolution. These observations are needed to better understand the transient surface energy balance, influenced by near-surface air temperatures and water fluxes ranging from evapotranspiration to snowmelt. From geostationary orbit, the GOES Advanced Baseline Imager (ABI) instrument views the Earth from a fixed longitude above the equator. ABI images therefore have increasingly off-nadir view angles and increasingly larger pixel dimensions the further a point on the Earth's surface is from the sub-satellite point. In thermal infrared imagery from ABI, these 2+ km pixels blur together the different surface temperatures of heterogeneous mountain landscapes. We compared GOES-16 ABI band 14 (11.2 mu m) brightness temperatures to 90 m spatial resolution ASTER band 14 (11.3 mu m) and 1 km spatial resolution MODIS band 31 (11.03 mu m) brightness temperatures and investigated how differences change over space and time for a study region in the central Sierra Nevada of California for the 2017-2020 snow seasons. We demonstrated the necessity of orthorectifying ABI imagery of mountain terrain to correct for the parallax effect in off-nadir imagery. This reduced the mean difference between ABI and ASTER similar to 11 mu m brightness temperatures from 1.6 degrees C to 1.0 degrees C and increased the r-squared value between ABI and ASTER thermal infrared brightness temperatures from 0.43 to 0.93. The ABI brightness temperatures were found to more closely match those of forest canopy temperatures than snow surface (with RMS differences of 1.2 degrees C and 3.0 degrees C respectively), and those of sunlit slopes as opposed to slopes facing away from the sun (with RMS differences of 1.6 degrees C and 3.4 degrees C respectively), in coincident ASTER imagery. This work demonstrates the use of GOES ABI, and associated challenges, for observing surface temperatures of forested mountain environments with seasonal snow.

Automated summary

Thermal infrared imagery from GOES satellites provides an opportunity to observe mountain surface temperatures. Orthorectification is necessary to correct for the parallax effect in off-nadir imagery. ABI brightness temperatures closely match those of forest canopy temperatures.