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Climate Monitoring & Diagnostics Laboratory |
HATS: What's New?U.S. Dept. of Commerce / NOAA / OAR / CMDL / HATS |
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Climate Monitoring & Diagnostics Laboratory |
HATS: What's New?U.S. Dept. of Commerce / NOAA / OAR / CMDL / HATS |
1999
A
Record of Atmospheric Halocarbons during the Twentieth Century from Polar Firn
Air
James H. Butler1, Mark Battle2,5,
Michael L. Bender2,5, Stephen A. Montzka1, Andrew D.
Clarke1,3, Eric S. Saltzman4, Cara M. Sucher2,6,
Jeffrey P. Severinghaus2,7, James W. Elkins1
Abstract:
Measurements of trace gases in air
trapped in polar firn demonstrate that natural sources of chlorofluorocarbons,
halons, persistent chlorocarbon solvents, and sulphur hexafluoride are minimal
or non-existent. Atmospheric concentrations of these gases, reconstructed back
to the late nineteenth century, are consistent with atmospheric histories
derived from anthropogenic emission rates and known atmospheric lifetimes.
The measurements confirm the predominance of human activity in the
atmospheric budget of organic chlorine, and allow the estimation of atmospheric
histories of halogenated gases of combined anthropogenic and natural origin. The
pre-twentieth-century burden of methyl chloride was close to that at present,
while the burden of methyl bromide was probably over half of today's value.
For the press release click here.
For relevant data click here.
paper published in April 22, 1999 issue of Nature:
Present and Future Trends in the Atmospheric Burden of Ozone-Depleting Halogens
S. A. Montzka1, J. H. Butler1, J. W. Elkins1, T. M. Thompson1, A. D. Clarke2, and L. T. Lock2
Abstract: The burden of ozone-depleting chemicals in the lower atmosphere has been decreasing since 1994 as a result of the Montreal Protocol. Here, we show how individual chemicals have influenced this decline, in order to estimate how the burden could change in the near future. Our measurements of atmospheric concentrations of the persistent, anthropogenic chemicals that account for most ozone-depleting halogen in today’s stratosphere show decline stems predominantly from the decrease in the atmospheric load of trichloroethane (CH3CCl3), a previously common cleaning solvent. The influence of this chemical has now peaked, however, and will become much smaller over the next five to ten years. As this influence lessens, a decrease in the burden of ozone-depleting halogen will be sustained only if emissions of other halocarbons fall. Although emissions of most gases regulated by the Montreal Protocol have decreased substantially over the past ten years, emissions of the potent ozone-depleting gas CBrClF2 (halon-1211) have remained fairly constant during this period, despite stringent limits on production in developed countries since 1994. The consequent atmospheric accumulation of this halon is retarding the decline of ozone-depleting halogen in the atmosphere more than any other persistent gas.
For the press release click here.
For relevant data click here.
paper accepted for publication in the Journal of Geophysical Research:
Transport Into the Northern Hemisphere Lowermost Stratosphere Revealed By In Situ Tracer Measurements
Eric A. Ray1,2, Fred L. Moore1,2, James W. Elkins1, Geoffrey S. Dutton1,2, David W. Fahey4, Holger Vömel1,2, Samuel J. Oltmans1 and Karen H. Rosenlof2,4
Abstract: The Lightweight Airborne Chromatograph Experiment (LACE) has made in situ measurements of several long-lived trace gases in the upper troposphere and lower to middle stratosphere as part of the Observations of the Middle Stratosphere (OMS) balloon program. The tracers measured by LACE include several photolytic species (CFC-11, CFC-12 and halon-1211) as well as SF6. LACE measurements of these long-lived tracers as well as nearly simultaneous measurements of water vapor and CO2 are used to investigate transport into the lowermost stratosphere, a region where few in situ measurements exist. The measured photolytic species and water vapor are used in a simple mass balance calculation to estimate the mixture of tropospheric and overworld (q > 380 K) air in the lowermost stratosphere. In the northern midlatitudes during September 1996 most of the air in the lowermost stratosphere sampled at the flight location (34.5ƒN) was transported quasi-isentropically from the troposphere. Measurements from both a May 1998 midlatitude flight and a June 1997 high latitude flight (64.5ƒN) revealed the air sampled in the lowermost stratosphere to be dominated by downward advection from the overworld. Atmospheric SF6 and CO2 can uniquely reveal time and spatial scales of transport due to these species' large growth rates and subsequent latitudinal surface and free tropospheric gradients. Measurements in the lowermost stratosphere from the September northern midlatitude flight coupled with surface measurements of these species revealed a transport time scale of no more than 1.5 months from the surface to the lowermost stratosphere. The SF6 and CO2 mixing ratios were also consistent with mostly Northern Hemisphere tropospheric air in the lowermost stratosphere. These results point out the usefulness of high resolution in situ measurements of long-lived tracers to help determine time and spatial scales of transport in the region of the upper troposphere and lowermost stratosphere.
Paper accepted for publication in the Journal of Geophysical Research-Atmospheres, 1999
Closure of the total hydrogen budget of the northern extratropical lower stratosphere
D. F. Hurst,1,2 G. S. Dutton,1,2 P. A. Romashkin,1,2 P. R. Wamsley,1,2
F. L. Moore,1,2 J. W. Elkins1, E. J. Hintsa and E. M. Weinstock,
R. L. Herman, E. J. Moyer, D. C. Scott, R. D. May, and C. R. Webster
Abstract: Methane (CH4), molecular hydrogen (H2), and water vapor (H2O) were measured concurrently on board the NASA ER-2 aircraft during the 1995-1996 Stratospheric Tracers of Atmospheric Transport (STRAT) and 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaigns. Correlations between these three main hydrogen reservoirs in the northern extratropical lower stratosphere are examined to evaluate H2O production from CH4 and H2 oxidation. The expected ratio of stratospheric H2O production (PH2O) to CH4 destruction (LCH4) = 1.973 ± 0.003 is calculated from an evaluation of CH4 and H2 oxidation reactions and the relationship between H2 and CH4 mixing ratios measured during STRAT. Correlations between H2O and CH4 were tight and linear only for air masses with mean ages ³ 3.8 years, restricting this analysis predominantly to latitudes between 40° and 90°N and potential temperatures between 470 and 540 K. The mean observed DH2O/DCH4 (-2.15 ± 0.18) is in statistical agreement with the expected PH2O/LCH4. The annual mean stratospheric entry mixing ratio for H2O calculated from this slope is 4.0 ± 0.3 ppm. The quantity H2O + 2·CH4 is quasi-conserved at 7.4 ± 0.5 ppm in older air masses in the northern extratropical lower strato-sphere. Significant departure of H2O + 2·CH4 from the mean value is a sensitive indicator of processes which influence H2O without affecting CH4, such as dehydration in a polar vortex or near the tropical tropopause. No significant trend is observed in ER-2 aircraft data for H2O + 2·CH4 in the lower stratosphere from 1993 through 1997.
Paper accepted for publication in the Journal of Geophysical Research-Atmospheres, 1999
On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman-a hygrometer
Eric J. Hintsa, Elliot M. Weinstock, James G. Anderson, Randy D. May, Dale F. Hurst1,2
Abstract. In an effort to better constrain atmospheric water vapor mixing ratios and to understand the discrepancies between measurements of water vapor in the stratosphere and troposphere, we have carefully examined data from the Harvard Lyman-a photofragment fluorescence hygrometer, which flew on the NASA ER-2 aircraft from 1992 to 1997 during the SPADE, CEPEX, STRAT, and POLARIS missions. The instrument is calibrated in the laboratory before and after each deployment, and the calibration is checked by direct absorption measurements in the troposphere and lowermost stratosphere. On certain flights, the ER-2 flew level tracks in which water vapor varied by up to 80 ppmv, under nearly constant atmospheric conditions. These flights provide a stringent test of our calibration via direct absorption, and indicate agreement to within 3%. During the 1997 POLARIS mission, our Lyman-a instrument was compared with a new diode laser hygrometer from the Jet Propulsion Laboratory. Overall agreement was 5% during the June/July deployment, and 1% for potential temperatures of 490 to 540K. The accuracy of our instrument is shown to be ±5%, with an additional offset of at most 0.1 ppmv. Data from this instrument, combined with simultaneous measurements of CH4 and H2, are therefore ideal for studies of the hydrogen budget of the lower stratosphere.
1998
paper published in the Journal of Geophysical Research, Vol., 103, No. D1, p. 1503-1511:
Growth and Distribution of Halons in the Atmosphere
James H. Butler1, Stephen A. Montzka1, Andrew D. Clarke2, Jürgen M. Lobert2,3,
and James W. Elkins1
Abstract: The atmospheric burden of halons has continued to increase in recent years, despite an international ban on their production and sales in developed nations as of 1 January 1994. Halon emissions persist because of a lack of suitable substitutes for critical uses as fire extinguishants. As of 1 January 1997, halons H-1301 (CBrF3), H-1211 (CBrClF2), and H-2402 (CBr2F4) were present in the troposphere at 2.3±0.1, 3.5±0.1, and 0.45±0.03 pmol mol-1. During 1995-96, the tropospheric mole fraction of H-1301 increased at 0.044±0.011 pmol mol-1 y-1, while that for H-1211 grew at 0.16±0.016 pmol mol-1 y-1. These increases are significant and of concern because of the efficiency of bromine in depleting stratospheric ozone and because of the long atmospheric lifetimes of these gases. Given the current atmospheric record and the reported amount of halon produced before the ban on their production, emission of H-1301 at the 1995-96 rate could continue for another 40 years, but H-1211 would be depleted in 8-12 years. Exemptions to the ban on production may extend these periods. Tropospheric H-2402 is increasing at 9±1 fmol mol-1 y-1, but historical data on its production and use are lacking.
paper published in the Journal of Geophysical Research, Vol., 103, No. D19, p. 25,299-25,306:
Recent Trends in the Variability of Halogenated Trace Gases over the United States
Dale, F. Hurst1,2, Peter S. Bakwin1,2, and James W. Elkins1
Abstract: Recent trends in the atmospheric variability of seven halogenated trace gases are determined from three years (November 1994 through October 1997) of hourly gas chromatographic measurements at a 610 m tower in North Carolina and 17 months (June 1996 through October 1997) of similar measurements at a 450 m tower in Wisconsin. Production of five of these gases, CCl3F (CFC-11), CCl2F2 (CFC-12), CCl2FCClF2 (CFC-113), CH3CCl3 (methyl chloroform), and CCl4 (carbon tetrachloride), is now strictly regulated in the United States and other developed countries under international legislation. C2Cl4 (tetrachloroethene) and SF6 (sulfur hexafluoride) are currently produced without restriction, but requests for voluntary cutbacks in C2Cl4 emissions have been made, at least in the United States. Atmospheric variability of these gases is examined at several sampling heights on the towers, but trends are deduced using only nighttime data at the top sampling level of each tower to minimize variability driven by local emissions and the diurnal cycle of the planetary boundary layer, leaving regional emissions as the main source of day-to-day variability. Significant downward trends are determined for CFC-12, CFC-113, CH3CCl3, and C2Cl4 variability at both towers, reflecting decreased emissions of these gases in two regions of the United States. Trends in CFC-11, CCl4, and SF6 variability at both towers are not significantly different from zero.
paper published in the Journal of Geophysical Research, Vol., 103, No. D1, p. 1513-1526:
Distribution of Halon-1211 in the Upper Troposphere and Lower Stratosphere and the 1994 total bromine budget
Paula R. Wamsley1,2, J. W. Elkins1, D. W. Fahey4, G. S. Dutton1,2, C. M. Volk1,2, R. C. Myers1, S. A. Montzka1, J. H. Butler1, A. D. Clarke1,2, P. J. Fraser, L. P. Steele, M. P. Lucarelli, E. L. Atlas, S. M. Schauffler, D. R. Blake, F. S. Rowland, R. M. Stimpfle, K. R. Chan, D. K. Weisenstein, and M. K. W. Ko,
Abstract: We report here on the details of the first, in situ, real-time measurements of H-1211 (CBrClF2) and sulfur hexafluoride (SF6) mixing ratios in the stratosphere up to 20 km. Stratospheric air was analyzed for these gases and others with a new gas chromatograph, flown aboard a National Aeronautics and Space Administration ER-2 aircraft as part of the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft mission conducted in 1994. The mixing ratio of SF6, with its nearly linear increase in the troposphere, was used to estimate the mean age of stratospheric air parcels along the ER-2 flight path. Measurements of H-1211 and mean age estimates were then combined with simultaneous measurements of CFC-11 (CCl3F), measurements of brominated compounds in stratospheric whole air samples, and records of tropospheric organic bromine mixing ratios to calculate the dry mixing ratio of total bromine in the lower stratosphere and its partitioning between organic and inorganic forms. We estimate that the organic bromine-containing species were almost completely photolyzed to inorganic species in the oldest air parcels sampled. Our results for inorganic bromine are consistent with those obtained from a photochemical, steady state model for stratospheric air parcels with CFC-11 mixing ratios greater than 150 ppt. For stratospheric air parcels with CFC-11 mixing ratios less than 50 ppt (mean age greater than or equal to 5 years) we calculate inorganic bromine mixing ratios that are approximately 20% less than the photochemical, steady state model. There is a 20% reduction in calculated ozone loss resulting from bromine chemistry in old air relative to some previous estimates as a result of the lower bromine levels.
Paper published in Tellus Ser. B, 50, 401-415, 1998
Measurements of carbon dioxide on very tall towers: results of the NOAA/CMDL program
Peter S. Bakwin1, Pieter P. Tans1, Dale F. Hurst2, and Conglong Zhao2
Abstract: Measurements of carbon dioxide (CO2) mixing ratios have been carried out since 1992 on a 610-m tall communications tower in North Carolina and since 1994 on a 447-m tall tower in Wisconsin. The data provide insights into the influence of pollution (fossil fuel combustion), biological exchange, boundary layer dynamics, and advective transport of CO2 mixing ratios over the continents. In this paper, we provide an overview of the data, describe access to the data, and suggest ways in which these results could be used to constrain model estimates of covariance between terrestrial ecosystem fluxes of CO2 and diurnal and seasonal variations of planetary boundary layer mixing.
Affiliations:
1
Climate Monitoring and Diagnostics Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 803032
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 803093
Now at Center for Clouds, Chemistry & Climate, Scripps Institution of Oceanography, La Jolla, CA 920934
NOAA/Aeronomy Laboratory, Boulder, CO |
Halocarbons & other Atomspheric Trace Species 325 Broadway R/E/CG1 Boulder, CO 80303 For more information contact: James W. Elkins |
