Infrared Atmospheric Sounding Interferometer correlation interferometry for the retrieval of atmospheric gases: the case of H_(2)O and CO_(2)

摘要

Correlation interferometry is a particular application of Fourier transform spectroscopy with partially scanned interferograms. Basically, it is a technique to obtain the difference between the spectra of atmospheric radiance at two diverse spectral resolutions. Although the technique could be exploited to design an appropriate correlation interferometer, in this paper we are concerned with the analytical aspects of the method and its application to high-spectral-resolution infrared observations in order to separate the emission of a given atmospheric gas from a spectral signal dominated by surface emission, such as in the case of satellite spectrometers operated in the nadir looking mode. The tool will be used to address some basic questions concerning the vertical spatial resolution of H_(2)O and to develop an algorithm to retrieve the columnar amount of CO_(2). An application to complete interferograms from the Infrared Atmospheric Sounding Interferometer will be presented and discussed. For H_(2)O, we have concluded that the vertical spatial resolution in the lower troposphere mostly depends on broad features associated with the spectrum, whereas for CO_(2), we have derived a technique capable of retrieving a CO_(2) columnar amount with accuracy of approx= +- 7 parts per million by volume at the level of each single field of view.