Friday, 7 June 2002
Atmospheric trace gas and aerosol remote sensing by nadir viewing thermal emission Fourier Transform spectrometer.
Nikita S. Pougatchev, Hristopher Newport University, Hampton, VA; and I. N. Sokolik, W. L. Smith, D. K. Zhou, and S. V. Kireev
Downward looking thermal emission Fourier Transform spectrometer (NAST-I) was flown on a high altitude Proteus airplane over northern Pacific. Upwelling thermal emission spectra were recorded at a spectral resolution of 0.24 cm-1. The spectra were used for retrieval of vertical profiles of carbon moxide (CO) and identification of a spectral signature of mineral aerosol (dust) in IR spectral region. The Proteus campaign was flown over the same geographical area and at the same time period as NASA's TRACE-P aircraft mission. That gave us an opportunity to compare NAST-I remote sensing data to high accuracy in situ TRACE-P CO measurements. We demonstrated that our retrievals reproduce a morphology of in situ measured profiles and absolute CO values reasonably well. We also compared our retrievals to CO satellite measurements performed by Measurement Of Pollution In The Troposphere (MOPITT) instrument. We concluded that the results are in a good agreement, what makes the NAST-I a valuable tool for validation of spaceborne sensors.
On March 12, 2001 an outflow of continental dust into Yelow Sea was detected by a spceborne SEAWIFS instrument. Analysis of NAST-I IR spectra taken on the same date over the same area reveals that continuum in 900 cm-1 spectral region has a specrtal dependence that can not be explained by gaseous components or clouds. Based on modeling of mineral aerosol optical properties we atributed that phenomenon to the presence of a significant amount of dust in the atmosphere.
Geosyncronus Imaging Fourier Transform Spectrometer (GIFTS) was selected by NASA for New Millennium Program EO-3 mission. One of the objectives of the mission is to demonstrate the GIFTS capability to measure atmospheric CO and ozone. To assess a fesibility of these mesurents, NAST-I spectra were reduced to the GIFTS spectral resolution, i.e., 0.6 cm-1, then CO and ozone profiles were retrieved from the lower resolution spectra. Comparison of the results demostrated that reduction of the spectral resolution to 0.6 cm-1 does not compromise a vertical resolution attainable.
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