[1] The High Resolution Dynamics Limb Sounder (HIRDLS) experiment was designed to provide global temperature and composition data on the region from the upper troposphere to the mesopause with vertical and horizontal resolution not previously available. The science objectives are the study of small-scale dynamics and transports, including stratosphere-troposphere exchange, upper troposphere/lower stratosphere chemistry, aerosol, cirrus and PSC distributions, and gravity waves. The instrument features 21 channels, low noise levels, high vertical resolution, and a mechanical cooler for long life. During launch most of the optical aperture became obscured, so that only a potion of an optical beam width at a large azimuth from the orbital plane on the side away from the Sun can see the atmosphere. Irrecoverable loss of capabilities include limitation of coverage to the region 65°S-82°N and inability to obtain longitudinal resolution finer than an orbital spacing. While this optical blockage also impacted radiometric performance, extensive effort has gone into developing corrections for the several effects of the obstruction, so that radiances from some of the channels can be put into retrievals for temperature. Changes were also necessary for the retrieval algorithm. The validation of the resulting temperature retrievals is presented to demonstrate the effectiveness of these corrections. The random errors range from $0.5 K at 20 km to $1.0 at 60 km, close to those predicted. Comparisons with high-resolution radiosondes, lidars, ACE-FTS, and ECMWF analyses give a consistent picture of HIRDLS temperatures being 1-2 K warm from 200 to 10 hPa and within ±2 K of standards from 200 to 2 hPa (but warmer in the region of the tropical tropopause), above which HIRDLS appears to be cold. Comparisons show that both COSMIC and HIRDLS can see small vertical features down to about 2 km

We have used a high resolution infrared spectrometer aboard the NASA Wallops Flight Facility Electra aircraft to measure the total column amount of SO2, O3, and HCl above the aircraft while flying over the Caribbean three weeks after the June 15 eruption of Mt. Pinatubo in the Philippines, South of 20°N latitude we observed columns of SO2 ranging from 2.0 × 1016 to 3.7 × 1016 molecules‐cm−2. In addition, the column amount of HCl averaged 1.5 × 1015 molecules‐cm−2 in the region of the plume. This may represent a small increase in HCl above the amount, estimated from our previous measurements, that would have been present had there been no volcanic eruption, but the increase is substantially less than that seen following the 1982 eruptions of El Chichón [Mankin and Coffey, 1984].

Spectroscopic observations of the total column amount of hydrogen chloride above an altitude of 12 kilometers in the latitude range 20 degrees to 40 degrees N have been made both before and 3 to 6 months after the eruptions of El Chichón Volcano in March and April 1982. In the region of the cloud of volcanic aerosols, the hydrogen chloride total column after the eruptions increased by approximately 40 percent, even after allowance is made for the global secular increase in hydrogen chloride of 5 percent per year. The column amounts of hydrogen fluoride show no such increase.

No abstract

Abstract. An intercomparison of four Fourier transform infrared (FTIR) spectrometers, operated side by side by Jet Propulsion Laboratory (JPL), National Center for Atmospheric Research, and National Physical Laboratory groups, using two different spectral fitting algorithms, was conducted at JPL's Table Mountain Facility (TMF) during November 1996. A "blind" comparison of retrieved vertical column amounts, of preselected trace gases in preselected microwindows (mw), and subsequent reanalysis of the results are described. The species analyzed are N2 (3 mw), HF (1 mw), HC1 (1 mw), CH4 (1 mw), 03 (2 mw), N20 (2 mw), HNO3 (2 mw), and CO2 (1 mw). The column agreements from the "blind" phase were within 0.5-2%, except that for HNO3, HF, and 03 the disagreement of the results was up to 10%, 5%, and 4%, respectively. It was found that several systematic effects were neglected in the "blind" phase analysis. Taking these into account in the postanalysis reduced the disagreements to 0.5-1.0% for most cases, and to less than 4%, 3%, and 1% for HNO3, HF, and 03 respectively. It was concluded that zero offsets caused by detector nonlinearity were the main cause of the large errors in HNO3 and other gases (i.e., CO2) retrieved from the HgCdTe spectra. At shorter wavelengths (i.e., HF) we conclude that incomplete modeling of the instrument line shapes (ILS) was the main cause of column differences larger than 1%.

Hydrogen chloride and hydrogen fluoride are important sinks in the stratosphere for free halogens. The major sources of chlorine and fluorine in the stratosphere are anthropogenic; therefore a measurement of HC1 and HF gives information about the magnitude of anthropogenic effects on stratospheric chemistry and may give some information about the stratospheric hydroxyl concentration as well. We have determined the total column amount of HCI and HF above 12 km by measuring infrared absorption spectra with a high-resolution Fourier transform spectrometer flown on a jet aircraft. The HC1 column varies from 0.7 x 10 •5 molecules-cm -'• near the equator to 2.7 x 10 •5 molecules-crn -'• at 70øN; the HF column is about a factor of 5 lower. The HCI:HF ratio is almost independent of latitude, and neither constituent shows substantial seasonal or diurnal variation. At mid-latitudes the data from 1978 to 1982 show an annual increase of 5% per year for HC1 and 12% per year for HF. INTRODUCTION One of the major chemical cycles controlling the concentration of ozone in the stratosphere is the catalytic destruction of ozone by free chlorine and chlorine monoxide I-Stolarski and Cicerone, 1974]. The principal source for free chlorine in the stratosphere is believed to be photolysis of the chlorofluoromethanes (CFM's) F-11 (CFCI3) and F-12 (CF2C12). These very stable species are released in the troposphere by man's activities and diffuse slowly to altitudes where they can be photolyzed by solar ultraviolet radiation [Molina and Rowland, 1974]. The principal sink for chlorine is the production of HC1 and its subsequent diffusion to the troposphere and rainout. HC1 also serves as a temporary reservoir for chlorine in the stratosphere, from which the chlorine can be released by reaction with hydroxyl radicals. There are other sources of stratospheric chlorine than CFM's; these include naturally produced methyl chloride and anthropogenic sources such as carbon tetrachloride and methyl chloroform. No substantial sources of fluorine in the stratosphere other than CFM's [Cicerone, 1981] have been identified. When CFM's are photolyzed, the fluorine is quickly incorporated in HF, which is relatively stable; fluorine does not directly play an important role in the chemistry of the stratosphere. Measurements of HF and of the ratio of HF to HCI provide an indication of the relative importance of CFM's and other sources of stratospheric chlorine. Further, because HF is practically inert in the stratosphere while HCI reacts with OH, variations in the profile of HF and HCI give indirect evidence of the OH chemistry [Sze, 1978; Sze and Ko, 1981]. Therefore, it is useful to obtain a data set for HF and HC1 that is measured simultaneously over as wide a range of conditions as possible. There have been a number of measurements of HC1 and HF in the stratosphere by both in-situ and remote sensing techniques. The first measurements were by collection on base impregnated filters [Lazrus et al., 1975]. The vertical profile of acidic chloride vapor, whic...

The importance Of NOx compounds to stratospheric chemistry has been clearly established. We report below on a program to measure latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2, and HNO3 amounts. Through the use of airborne Fourier transform absorption spectroscopy, we determine simultaneously column amounts above 12 km of the four molecules listed above. Nitrous oxide (N2O) is found to have a fairly uniform distribution with latitude and season, with a stratospheric column abundance of 8.1 × 1017 molecules cm−2. Nitric oxide (NO) amounts are shown to decrease with increasing latitude in winter. A 50% decrease in high latitude winter amounts is observed as compared with low latitude values near 3.0 × 1015 molecules cm−2. Nitrogen dioxide (NO2) stratospheric amounts increase in summer with increasing latitude. Equatorial values are near 3.0 × 1015 molecules cm−2 above 12 km. A factor of 3–4 increase in higher latitude summertime NO2, as compared to winter NO2, is observed. Nitric acid (HNO3) amounts show a general increase toward higher latitudes and a marked increase in mid‐latitude winter as compared to summer. Winter amounts may be highly variable with a value near 1.0 × 1016 molecules cm−2.

of the observed column ratio (C1ONO2 + HC1)/HF as an indicator for chlorine activation. Current measurement uncertainties limit the degree of activation which can be unambiguously detected using this observed quantity, but we can determine that chlorine-activated air was observed above Aberdeen (58øN) on 6 days in late