Rodolphe Zander

Atmospheric Chemistry Experiment (ACE): Mission overview

SCISAT-1, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sensing of the Earths atmosphere. It was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 μm (750-4400 cm-1). The satellite also features a dual spectrophotometer known as MAESTRO with wavelength coverage of 285-1030 nm and spectral resolution of 1-2 nm. A pair of filtered CMOS detector arrays records images of the Sun at 0.525 and 1.02 μm. Working primarily in solar occultation, the satellite provides altitude profile information (typically 10-100 km) for temperature, pressure, and the volume mixing ratios for several dozen molecules of atmospheric interest, as well as atmospheric extinction profiles over the latitudes 85°N to 85°S. This paper presents a mission overview and some of the first scientific results. Copyright 2005 by the American Geophysical Union.

The Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment: Deployment on the ATLAS space shuttle missions

The ATMOS Fourier transform spectrometer was flown for a fourth time on the Space Shuttle as part of the ATLAS-3 instrument payload in November 1994. More than 190 sunrise and sunset occultation events provided measurements of more than 30 atmospheric trace gases at latitudes 3–49°N and 65–72°S, including observations both inside and outside the Antarctic polar vortex. The instrument configuration, data retrieval methodology, and mission background are described to place in context analyses of ATMOS data presented in this issue.

Correlations of stratospheric abundances of NO y , O3, N2O, and CH4 derived from ATMOS measurements

Correlations are presented for [NO y ] relative to [N 2 O] and [O 3 ] derived from measurements from the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument from a wide range of altitudes and latitudes, including the tropics for which previous analyses have not extended above ∼20 km. Relationships for [O 3 ] versus [N 2 O] are also given. The results are shown to be in good agreement with aircraft- and balloon-based observations. Distinct correlations are observed for the tropics, the springtime polar vortex, and the extratropics-extravortex regions. These correlations demonstrate rapid production of NO y and O 3 in the tropical middle stratosphere and episodic export of air from this region to higher latitudes. Isolation of air within the developing polar vortices in the fall is also shown. Arctic vortex data from April 1993 appear to indicate denitrification of 25-30%, which is evident as a 3.0-4.5 ppb deficit in [NO,] when the vortex [NO y ]:[N 2 O] correlation is compared with the extravortex correlation. A mixture of air descended from above 40 km with air from lower altitudes can fully account for this deficit in [NO y ], in addition to approximately half of an apparent Arctic ozone loss of 50-60%, as inferred by comparison of the vortex and extravortex [O 3 ]:[N 2 O] correlations. Comparison of Antarctic vortex and extravortex correlations from November 1994 similarly show a 60-80% deficit in [NO y ] and 80-100% deficit in [O 3 ]; at least half of this apparent denitrification and ozone loss can be attributed to mixing of air descended from higher altitudes with air from lower altitudes.

Long‐term trends of inorganic chlorine from ground‐based infrared solar spectra: Past increases and evidence for stabilization

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with infrared Fourier transform spectrometers at nine NDSC (Network for the Detection of Stratospheric Change) sites in both Northern and Southern Hemispheres. The data sets span up to 24 years and most extend until the end of 2001. The time series of Cl-y (defined here as the sum of the HCl and ClONO2 columns) from the three locations with the longest time-span records show rapid increases until the early 1990s superimposed on marked day-to-day, seasonal and inter-annual variability. Subsequently, the buildup in Cl-y slows and reaches a broad plateau after 1996, also characterized by variability. A similar time evolution is also found in the total chlorine concentration at 55 km altitude derived from Halogen Occultation Experiment (HALOE) global observations since 1991. The stabilization of inorganic chlorine observed in both the total columns and at 55 km altitude indicates that the near-global 1993 organic chlorine (CCly) peak at the Earths surface has now propagated over a broad altitude range in the upper atmosphere, though the time lag is difficult to quantify precisely from the current data sets, due to variability. We compare the three longest measured time series with two-dimensional model calculations extending from 1977 to 2010, based on a halocarbon scenario that assumes past measured trends and a realistic extrapolation into the future. The model predicts broad Cl-y maxima consistent with the long-term observations, followed by a slow Cl-y decline reaching 12-14% relative to the peak by 2010. The data reported here confirm the effectiveness of the Montreal Protocol and its Amendments and Adjustments in progressively phasing out the major man-related perturbations of the stratospheric ozone layer, in particular, the anthropogenic chlorine-bearing source gases. (Less)

Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment Version 3 data retrievals

Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space Shuttle missions (in 1985, 1992, 1993, and 1994), profiles from more than 350 occultations were retrieved from the upper troposphere to the lower mesosphere. Previous results were unreliable for tropospheric retrievals, but with a new global-fitting algorithm profiles are reliably returned down to altitudes as low as 6.5 km (clouds permitting) and include notably improved retrievals of H2O, CO, and other species. Results for stratospheric water are more consistent across the ATMOS spectral filters and do not indicate a net consumption of H2 in the upper stratosphere. A new sulfuric-acid aerosol product is described. An overview of ATMOS Version 3 processing is presented with a discussion of estimated uncertainties. Differences between these Version 3 and previously reported Version 2 ATMOS results are discussed. Retrievals are available at http://atmos.jpl.nasa.gov/atmos.

The 1985 chlorine and fluorine inventories in the stratosphere based on ATMOS observations at 30° north latitude

The set of high-resolution infrared solar observations made with the Atmospheric Trace Molecule Spectroscopy (ATMOS)-Fourier transform spectrometer from onboard Spacelab 3 (30 April-1 May 1985) has been used to evaluate the total budgets of the odd chlorine and fluorine chemical families in the stratosphere. These budgets are based on volume mixing ratio profiles measured for HCl, HF, CH3Cl, ClONO2, CCl4, CCl2F2, CCl3F, CHClF2, CF4, COF2, and SF6 near 30° north latitude. When including realistic concentrations for species not measured by ATMOS, i.e., the source gases CH3CCl3 and C2F3Cl3 below 25 km, and the reservoirs ClO, HOCl and COFCl between 15 and 40 km (five gases actually measured by other techniques), the 30° N zonal 1985 mean total mixing ratio of chlorine, Cl, was found to be equal to (2.58±0.10) ppbv (parts per billion by volume) throughout the stratosphere, with no significant decrease near the stratopause. The results for total fluorine indicate a slight, but steady, decrease of its volume mixing ratio with increasing altitude, around a mean stratospheric value of (1.15±0.12) ppbv. Both uncertainties correspond to one standard deviation. These mean springtime 1985 stratospheric budgets are commensurate with values reported for the tropospheric Cl and F concentrations in the early 1980s, when allowance is made for the growth rates of their source gases at the ground and the time required for tropospheric air to be transported into the stratosphere. The results are discussed with emphasis on conservation of fluorine and chlorine and the partitioning among source, sink, and reservoir gases throughout the stratosphere.

Free tropospheric CO, C2H6, and HCN above central Europe: Recent measurements from the Jungfraujoch station including the detection of elevated columns during 1998

Time series of free tropospheric carbon monoxide (CO), ethane (C 2 H 6 ), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the Jungfraujoch (ISSJ) at 3.58-km altitude in the Swiss Alps (latitude 46.55°N, 7.98°E longitude). The free troposphere was assumed to extend from 3.58 to 11 km altitude, and the related columns were derived for all three molecules from high spectral resolution infrared solar spectra recorded between January 1995 and October 1999. The three molecules show distinct seasonal cycles with maxima during winter for CO and C 2 H 6 , and during spring for HCN. These seasonal changes are superimposed on interannual variations. The tropospheric columns of all three molecules were elevated during 1998. Increases were most pronounced for HCN with enhanced values throughout the year, up to a factor of 2 in January 1998 when compared to averages of the other years. The increased tropospheric columns coincide with the period of widespread wildfires during the strong El Nino warm phase of 1997-1998. The emission enhancements above ISSJ are less pronounced, and they peaked after the increases measured above Mauna Loa (19.55°N, 155.6°W). Tropospheric trends for CO, C 2 H 6 , and HCN of (2.40 ± 0.49), (0.47 ± 0.64), and (7.00 ± 1.61)% yr 1 (1 sigma) were derived for January 1995 to October 1999. However, if 1998 measurements are excluded from the fit, CO and HCN trends that are not statistically significant, and a statistically significant decrease in the C 2 H 6 tropospheric column, are inferred. Comparisons of the infrared CO columns with CO in situ surface measurements suggest that the CO free tropospheric vertical volume mixing ratio profile generally decreases with altitude throughout the year.

The 1994 northern midlatitude budget of stratospheric chlorine derived from ATMOS/ATLAS‐3 observations

Volume mixing ratio (VMR) profiles of the chlorine-bearing gases HCl, ClONO2, CCl3F, CCl2F2, CHClF2, CCl4, and CH3Cl have been measured between 3 and 49° northern- and 65 to 72° southern latitudes with the Atmospheric Trace MOlecule Spectroscopy (ATMOS) instrument during the ATmospheric Laboratory for Applications and Science (ATLAS)-3 shuttle mission of 3 to 12 November 1994. A subset of these profiles obtained between 20 and 49°N at sunset, combined with ClO profiles measured by the Millimeter-wave Atmospheric Sounder (MAS) also from aboard ATLAS-3, measurements by balloon for HOCl, CH3CCl3 and C2Cl3F3, and model calculations for COClF indicates that the mean burden of chlorine, ClTOT, was equal to (3.53±0.10) ppbv (parts per billion by volume), 1-sigma, throughout the stratosphere at the time of the ATLAS 3 mission. This is some 37% larger than the mean 2.58 ppbv value measured by ATMOS within the same latitude zone during the Spacelab 3 flight of 29 April to 6 May 1985, consitent with an exponential growth rate of the chlorine loading in the stratosphere equal to 3.3%/yr or a linear increase of 0.10 ppbv/yr over the Spring-1985 to Fall-1994 time period. These findings are in agreement with both the burden and increase of the main anthropogenic Cl-bearing source gases at the surface during the 1980s, confirming that the stratospheric chlorine loading is primarily of anthropogenic origin.

Observed trends in total vertical column abundances of atmospheric gases from IR solar spectra recorded at the Jungfraujoch

Since 1984, about 15000 high quality infrared solar spectra have beenrecorded with state-of-the-art grating and Fourier transform spectrometersat the International Scientific Station of the Jungfraujoch, Switzerland.Nonlinear least squares spectral curve fitting of selected microwindowscontaining isolated and well characterized lines of 20 telluric gases haveallowed to retrieve their total vertical column abundances above thestation, leading to observational data bases essential to derive long- andshort-term changes experienced by these species during the last 12 years. Inthis paper, we focus on atmospheric gases of particular interest within thecontext of the EUROTRAC/TOR (Tropospheric Ozone Research) project; secularevolution as well as seasonal cycles of the minor constituentsCH4, CO and of the trace gasesC2H6, OCS, C2H2, HCNand H2CO are reported and discussed. The long-livedN2O is included as a tracer of the dynamic activity of theatmosphere.

Stratospheric profiles of heavy water vapor isotopes and CH3D from analysis of the ATMOS Spacelab 3 infrared solar spectra

Stratospheric volume mixing ratio profiles of H218O, H217O, HDO, and CH3D near latitudes of 30°N and 47°S have been retrieved from ∼0.01-cm−1 resolution infrared solar occultation spectra recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Spacelab 3 shuttle mission (April 29 to May 6, 1985). Improved heavy isotope water vapor and CH3D spectroscopic parameters determined from ∼0.005- to 0.01-cm−1 resolution room temperature laboratory spectra have been used in the retrievals. The profiles of the three water vapor isotopes show an increase in the volume mixing ratio with altitude over the range of measurements (20 to 54 km for H218O, 20 to 46 km for H217O, and 20 to 34 km for HDO). Deuterium-to-hydrogen and heavy-to-normal oxygen isotope ratio profiles have been calculated by dividing the retrieved isotopic profiles by the previously reported profiles of H216O and CH4 obtained from the same spectral data and then referencing these results to the isotopic composition of standard mean ocean water (SMOW). At 20 km the 18O/16O ratio in H2O is slightly (∼8%) depleted relative to SMOW; this ratio increases with altitude and is slightly positive above ∼36 km. No evidence has been found for the large 18O enhancements reported previously. The 17O/16O water vapor results are similar to those for 18O/16O. The ATMOS measurements show depletions of ∼63% in the D/H content of water vapor near 20 km and an increase in this ratio with altitude up to 34 km. The D/H ratio in stratospheric methane is close to the isotopic ratio in SMOW over the 18 to 28 km altitude range. No differences between the water vapor or methane isotopic compositions at 30°N and 47°S were detected. The results are compared with previously reported measurements and calculations.