ABSTRACT
Remote measurements of the Earth’s atmospheric state using microwave and infrared wavelengths have been carried out for many years [1,2]. Physical considerations involving the use of these spectral regions include the relatively high cloud penetrating capability at microwave wavelengths and the relatively sharp weighting functions at infrared wavelengths, particularly in the shortwave region near 4 μm where Planck nonlinearity further increases temperature sensitivity. Infrared spectrometer technology has advanced markedly over the past 15 years or so to allow the simultaneous spectral sampling of thousands of bands spaced along narrow atmospheric absorption features [3]. The Atmospheric InfraRed Sounder (AIRS), launched in May 2002, measures 2378 channels from 3.7 to 15.4 μm [4] and the Infrared Atmospheric Sounding Interferometer, launched in 2006, measures 8461 channels from 3.6 to 15.5 μm [5]. These sensors, and similar sensors to be launched as part of the National polar-orbiting operational environmental satellite system Preparatory Project (NPP) and Metosat Third Generation systems, substantially improve atmospheric sounding through the use of hyperspectral measurements, which yield greater vertical resolution throughout the atmosphere [6].
