Carbon monoxide mixing ratios over Oklahoma between 2002 and 2009 retrieved from Atmospheric Emitted Radiance Interferometer spectra

摘要

CO mixing ratios for the lowermost 2-km atmospheric layer were retrievedfrom downwelling infrared (IR) radiance spectra of the clear sky measuredbetween 2002 and 2009 by a zenith-viewing Atmospheric Emitted RadianceInterferometer (AERI) deployed at the Southern Great Plains (SGP)observatory of the Atmospheric Radiation Measurements (ARM) Program nearLamont, Oklahoma. A version of a published earlier retrieval algorithm wasimproved and validated. Archived temperature and water vapor profilesretrieved from the same AERI spectra through automated ARM processing wereused as input data for the CO retrievals. We found the archived water vaporprofiles required additional constraint using SGP Microwave Radiometerretrievals of total precipitable water vapor. A correction for scatteredsolar light was developed as well. The retrieved CO was validated usingsimultaneous independently measured CO profiles from an aircraft. Thesetropospheric CO profiles were measured from the surface to altitudes of4572 m a.s.l. once or twice a week between March 2006 and December 2008.The aircraft measurements were supplemented with ground-based COmeasurements using a non-dispersive infrared gas correlation instrument atthe SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km tocreate full tropospheric CO profiles. Comparison of the profiles convolvedwith averaging kernels to the AERI CO retrievals found a squared correlationcoefficient of 0.57, a standard deviation of ±11.7 ppbv, a bias of-16 ppbv, and a slope of 0.92. Averaged seasonal and diurnal cycles measured bythe AERI are compared with those measured continuously in situ at the SGP inthe boundary layer. Monthly mean CO values measured by the AERI between 2002and 2009 are compared with those measured by the AIRS over North America,the Northern Hemisphere mid-latitudes, and over the tropics.