Retrieval of the carbon monoxide column densities using AIRS on EOS: validation of a prototype retrieval algorithm

Abstract

One goal of the atmospheric infrared sounder (AIRS), scheduled to fly on the EOS-PM1 satellite in 2000, is the global measurement of the atmospheric abundance of carbon monoxide (CO). ALthough it is primarily a temperature and humidity sounder for EOS, AIRS can resolve individual CO lines in a portion of the 1-0 vibration-rotation band of CO between 2170 and 2200 cm -1 , but with significant noise. Taking advantage of the almost regular spacing of these lines, we have developed an algorithm to retrieve the column density of CO from AIRS spectra using standard signal processing techniques for noise reduction. Detailed simulations indicate the capability to retrieve total column densities of CO to an accuracy of approximately 10 percent. Validation of our CO retrieval algorithm has been accomplished using a combination of in situ CO profiles acquired by an instrumented Cessna and nearly coincident infrared spectra obtained by the University of Wisconsin Madison's High-resolution Interferometer Sounder (HIS) flying onboard a NASA ER-2 during the Second Convection and Moisture Experiment in August, 1995. Excellent agreement was obtained between the retrieved CO abundance, approximately 90 ppbv, and the in situ profile above the boundary layer, approximately 80-100 ppbv. Additional HIS spectra obtained near Long Island, NY show enhanced CO levels, 1400-4300 ppb if confined to portions of the boundary layer, in the smoke plume downwind from forest fires near Westhampton, NY on August 25, 1995.