Study of Clear Sky, Low-Level Atmospheric Temperature Inversions Using Satellite Data

The near-surface atmosphere of the polar regions 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, and the High Resolution Infrared Radiation Sounder (HIRS) on NOAA's polar-orbiting satellites. The method is based on an empirical relationship between the inversion strength, defined as the temperature difference across the inversion, or height, defined as the altitude difference, and the difference between brightness temperatures in the 7.2 µm water vapor and 11 µm infrared window bands. Results indicate that inversion strength can be estimated unbiasedly with a root-mean-square error (RMSE) of 2-3 C. Inversion height can be estimated with a RMSE of 130-250 m. The retrieved inversion strength and height using this method are compared to the physical temperature profile retrievals for MODIS and the high spectral resolution Atmospheric Infrared Sounder (AIRS). Seasonal inversion strength and height characteristics are described with results from MODIS, and the annual cycle and trends in inversion properties are examined with 20-year HIRS and radiosonde datasets.