NORTHERN AND SOUTHERN-HEMISPHERE GROUND-BASED INFRARED SPECTROSCOPIC MEASUREMENTS OF TROPOSPHERIC CARBON-MONOXIDE AND ETHANE

crime series of CO and C2H6 measurements have been derived from high-r esolution infrared solar spectra recorded in Lauder, New Zealand (45.0 degrees S, 169.7 degrees E, altitude 0.37 km), and at the U.S. Nation al Solar Observatory (31.9 degrees N, 111.6 degrees W, altitude 2.09 k m) on Kitt Peak. Lauder observations were obtained between July 1993 a nd November 1997, while the Kitt Peak measurements were recorded betwe en May 1977 and December 1997. Both databases were analyzed with spect roscopic parameters that included significant improvements for C2H6 re lative to previous studies. Target CO and C2H6 lines were selected to achieve similar vertical samplings based on averaging kernels. These c alculations show that partial columns from layers extending from the s urface to the mean tropopause and from the mean tropopause to 100 km a re nearly independent. Retrievals based on a semiempirical application of the Rodgers optimal estimation technique are reported for the lowe r laver, which has a broad maximum in sensitivity in the upper troposp here. The Lauder CO and C2H6 partial columns exhibit highly asymmetric al seasonal cycles with minima in austral autumn and sharp peaks in au stral spring. The spring maxima are the result of tropical biomass bur ning emissions followed by deep convective vertical transport to the u pper troposphere and long-range horizontal transport. Significant year -to-year variations are observed for both CO and C2H6, but the measure d trends, (+0.37 +/- 0.57)% yr(-1) and (-0.64 +/- 0.79)% yr(-1), 1 sig ma, respectively, indicate no significant long-term changes. The Kitt Peak data also exhibit CO and C2H6 seasonal variations in the lower la yer with trends equal to (-0.27 +/- 0.17)% yr(-1) and (-1.20 +/- 0.35' )% yr(-1), 1 sigma, respectively. Hence a decrease in the Kitt Peak tr opospheric C2H6 column has been detected, though the CO trend is not s ignificant. Both measurement sets are compared with previous observati ons, reported trends, and three-dimensional model calculations.