Detection and analysis of clear-sky, low-level atmospheric temperature inversions with MODIS

The near-surface atmosphere of the polar region is characterized by temperature inversions throughout most of the year. However, radiosonde data are sparse, and numerical weather prediction models have relatively poor vertical resolution for boundary layer studies. A method is developed for detecting and estimating the characteristics of clear-sky, low-level temperature inversions using the Moderate Resolution Imaging Spectroradiometer ( MODIS) on the Terra and Aqua satellites. The method is based on an empirical relationship between the inversion strength, defined as the temperature difference across the inversion, or depth, defined as the altitude difference, and the difference between brightness temperatures in the 7.2-mum water vapor and 11-mum infrared window bands. Results indicate that inversion strength can be estimated unbiasedly with a root-mean-square error (rmse) of 2degrees-3degreesC and an R-2 of 0.80 - 0.97. Inversion depth can be estimated with an rmse of 130 - 250 m and an R-2 of 0.62 - 0.82. With MODIS, temperature inversions can be observed at a spatial resolution as high as 1 km(2) and a temporal sampling of up to 14 times per day, providing an opportunity for detailed studies of the spatial distribution and temporal evolution of the high-latitude boundary layer.