Simultaneous stratospheric measurements of H₂O, HDO, and CH₄ from balloon‐borne and aircraft infrared solar absorption spectra and tunable diode laser laboratory spectra of HDO

Abstract

High‐resolution infrared solar absorption spectra recorded from a balloon‐borne platform at 33‐km altitude and an aircraft at 12‐km altitude have been analyzed to derive simultaneous stratospheric concentrations of H2O, HDO, and CH4. The data were obtained near 33°N with the University of Denver interferometer during a balloon flight in October 1979 and with the NCAR interferometer aboard a Sabreliner aircraft in September 1982. The analysis of the balloon spectra indicates the H2O mixing ratio increased from 3.5 to 4.8 ppmv and the CH4 mixing ratio decreased from 1.15 to 0.70 ppmv between 18 to 38 km. Tunable diode laser laboratory spectra were recorded and analyzed to derive absolute intensities and air‐broadened half widths of selected lines of the v2 band of HDO. With these parameters, which are reported here, an HDO profile that increases from 0.61 ppbv near 18 km to 0.88 ppbv near 29 km is inferred from the balloon spectra, corresponding to a D/H ratio, normalized to the reference value of 158 atomic parts per million of Standard Mean Ocean Water (SMOW), of 0.55 to 0.67. The average D/H value of 0.40 above 12 km, derived from the aircraft spectra, provides additional spectroscopic evidence for a large depletion in the D content of water vapor in the lower stratosphere. The simultaneous vertical profiles for the three gases retrieved from the balloon spectra are consistent, within the estimated precision of the data (±10%), with methane oxidation as the sole source of stratospheric H2O in addition to H2O transported upward through the tropopause. However, there is an indication of a small increase in the total hydrogen in H2O and CH4 with altitude, and we believe more precise simultaneous measurements are required.

Stratospheric methane concentration profiles measured during the Balloon Intercomparison Campaigns

“…e. assuming the total hydrogen content of the stratosphere to be the result of the sum 2 x CH 4 + H20, its value at a typical altitude of 35 km derived from the present CH 4 data and H20 measurements made simultaneously with the same instrements are as follows : during BICI, 4.1 ppmv by NPL, and 7.0 ppmv by ULG; during BIC2, 3.4 ppmv by NPL, 5.8 ppmv by ULG, and 9.0 ppmv by ONERA. While the ULG results are in good agreement with similar sums derived by Pollock et al (1980), by Rinsland et al (1984), and by Jones et al (1986), giving an average of approximately 6 ppmv, the NPL values are definitely too low and the ONERA result somewhat high (a consequence of the large H20 concentration measured by ONERA above 30 km altitude). Even without the inclusion of H 2 (whose emission may be treated as a steady offset of approximately 0.5 ppmv; see Volz et al, 1981) the hydrogen budget 2 x CH 4 + H20 can be considered as a valuable criterion for judjing the consistency of closely related CH 4 and H20 measurements.…”

Basaltic fissure eruptions, plume heights, and atmospheric aerosols

“…The formation of so much stratospheric H2SO4 aerosol is not impossible. The unperturbed stratosphere contains (at least presently) 4 x 1015g of H20 and CH4 (Ellsaesser, 1983; Rinsland et al, 1984). Therefore, a volcanic supply of 2 x 1015g of sulfur could be entirely convened to H2SO4 without even taking into account the additional reducing gases (primarily H20) that would be erupted and entrained along with the principal SO2.…”

Modelling the budget of middle atmospheric water vapour isotopes

“…Johnson et al (2001a) applied a simple photochemical model with many simplifications, but inferred excellent agreement with own δD(H 2 O) and δ 18 O(H 2 O) balloon-borne observations conducted between 1989 and 1997. The major difference of the present model study compared to earlier work is first that all three stable isotope signatures δD(H 2 O), δ 17 O(H 2 O), and δ 18 O(H 2 O) both in the stratosphere as well as in the mesosphere are combined, and second that a large number of isotope exchange reactions and all isotope fractionation coefficients measured so far are considered. Special emphasis is put on the specific pathways of D, (i) Most stable isotope H 2 O data were collected using remote-sensing infrared spectroscopy techniques (Abbas et al, 1987;Carli and Park, 1988;Guo et al, 1989;Dinelli et al, 1991Rinsland et al, 1984Rinsland et al, , 1991Stowasser et al, 1999;Johnson et al, 2001;Kuang et al, 2003). They all reveal strong depletions of δD(H 2 O) with respect to V-SMOW which significantly decrease with altitude, from about -(660 ± 80)‰ at the tropical tropopause (Moyer et al, 1996;Johnson et al, 2001;Kuang et al, 2003;McCarthy et al, 2004) to typically -(450 ± 70)‰ at 40 km.…”