Detection and analysis of low-level temperature inversions with MODIS

Low-level atmospheric temperature inversions are ubiquitous at high latitudes during the polar winter. It has previously been shown that strong inversions over the Antarctic continent can be detected by examining the brightness temperature difference (BTD) between a water vapor absorption band at 6.7 μm and the infrared window at 11 μm. Under clear sky conditions this brightness temperature difference will be negative because the water vapor band, with a weighting function that peaks near 500 hPa, senses the warmer atmosphere near the top of the inversion while the window channel temperature is controlled primarily by surface emission. However, the method is not generally applicable to weaker or shallower inversions that are common in the Arctic and some parts of the Antarctic continent. In this paper we extend the work of Ackerman (1996) on inversion detection by incorporating two spectral bands whose weighting functions peak lower in the troposphere: the 7.2 μm water vapor band and the 13.3 μm carbon dioxide band of the Moderate-Resolution Imaging Spectroradiometer (MODIS). The brightness temperature differences 11-6.7 μm, 11-7.2 μm, and 13.2 μm are used to detect the presence and magnitude of low-level atmospheric temperature inversions under clear sky conditions during the polar night.