Infrared measurements of atmospheric gases above Mauna Loa, Hawaii, in February 1987

Infrared solar absorption spectra recorded at 0.02 cm −1 resolution from the National Oceanic and Atmospheric Administration (NOAA) Geophysical Monitoring for Climate Change (GMCC) program station at Mauna Loa, Hawaii (latitude 19.5°N, longitude 155.6°W, elevation 3.40 km), in February 1987 have been analyzed to determine simultaneous total vertical column amounts for 13 atmospheric gases. Average tropospheric concentrations of CO 2 , N 2 O, CH 4 , and CHClF 2 and the daytime diurnal variations of the total columns of NO and NO 2 have also been inferred. The retrieved total columns (in molecules cm −2 ) of the nondiurnally varying gases are 1.6±0.2×10 15 for HCl, 5.9±1.2 ×10 15 for HNO 3 , 2.0±0.2×10 21 for H 2 16 O, 4.4±0.7×10 18 for H 2 18 O, 2.7±0.1×10 17 for HDO, 2.3±0.2×10 19 for CH 4 , 5.0±0.5×10 21 for CO 2 , 6.7±0.8×10 18 for O 3 , 4.3±0.4×10 18 for N 2 O, 1.0±0.2×10 16 for C 2 H 6 , and 9.7±2.5×10 14 for CHClF 2 . We compare the total column measurements of HCl and HNO 3 with previously reported ground‐based, aircraft, and satellite measurements. The results for HCl are of particular interest because of the expected temporal increase in the concentration of this gas in the stratosphere. However, systematic differences among stratospheric HCl total column measurements from 1978 to 1980 and the absence of observations of free tropospheric HCl above Mauna Loa make it impossible to obtain a reliable estimate of the trend in the total burden of HCl. The measured HNO 3 total column is consistent with aircraft measurements from ∼12 km altitude. The O 3 total column deduced from the IR spectra agrees with correlative Mauna Loa Umkehr measurements within the estimated error limits. The column‐averaged D/H ratio of water vapor is (68±9)×10 −6 , which is 0.44±0.06 times the reference value of 155.76×10 −6 for standard mean ocean water (SMOW). This large depletion in the D content of water vapor is similar to published measurements of the upper troposphere and lower stratosphere. Average tropospheric concentrations deduced for CO 2 , N 2 O, and CH 4 are in good agreement with correlative NOAA GMCC surface data, indicating consistency between the measurement techniques for determining tropospheric volume mixing ratios. Results of the present study indicate that Mauna Loa is a favorable site for infrared monitoring of atmospheric gases. The site is particularly favorable for monitoring the tropospheric volume mixing ratios of long‐lived gases, since the high altitude of the tropopause reduces corrections required to account for the decrease in volume mixing ratio in the stratosphere.