HATS Publications
Here is a list of HATS publications. Currently, we have all of our first and
co-authored papers since 1993 in here. The publications are listed by year, latest on top,
the oldest at the bottom. The capitalized authors work or worked at NOAA/ERL during that
year, the hyperlinked author is the main NOAA/CMDL/HATS author whom you can contact by
clicking on the name. If the paper number (e.g. HATS-95-020) appears as a bold link, we
have that document downloadable as a Microsoft Word document or as a postscript document,
or online in HTML format. Just click on that number to see the options.
1997
HATS-97-001 (available
online, click identifier on left)
- J.M. LOBERT, S.A. YVON-LEWIS, J.H. BUTLER,
S.A. MONTZKA, and R.C. MYERS. Undersaturations of CH3Br
in the Southern Ocean. Geophys. Res. Lett. 24, 171-172, 1997.
Dry mole fractions of methyl bromide (CH3Br) in marine
boundary layer air and in air equilibrated with surface water were measured in the
Southern Ocean. Saturation anomalies were consistently negative at -36±7%. The observed
undersaturations do not support recently published predictions of highly supersaturated
Antarctic waters, but, instead, suggest a net uptake of atmospheric CH3Br
by cold, productive oceans. The observations do not appear to be supported by known
chemical degradation rates and present strong evidence for an unidentified, oceanic sink
mechanism such as biological breakdown. Our estimate for the global, net, oceanic sink for
atmospheric methyl bromide remains negative at -21 (-11 to -32) Gg y-1.
1996
HATS-96-001 (available
online, click identifier on left)
- YVON, S.A. and J.H. BUTLER. An improved
estimate of the oceanic lifetime of atmospheric CH3Br.
Geophysical Research Letters 23(1):53-56 (1996)
Previous estimates of the partial atmospheric lifetime of CH3Br
with respect to degradation in the ocean have not fully accounted for co-variation of
sea-surface and boundary layer properties. Here we substantially reduce uncertainty in
this calculation by using a coupled, ocean-atmosphere box model and a tightly gridded data
set of oceanic and atmospheric properties. The best estimate of the partial atmospheric
lifetime of CH3Br with respect to the ocean is 2.7 y
with a possible range, due mainly to the choice of computational procedures for critical
terms, of 2.4 to 6.5 y. This range is about one-third of that estimated previously. The
total atmospheric lifetime, based upon oceanic, atmospheric, and proposed soil losses with
all of their uncertainties, is 0.8 (0.6 to 1.4) y. Only 28% of this total uncertainty is
attributable to the uncertainty in oceanic loss.
HATS-96-002 (available
online, click identifier on left)
- J. W. ELKINS, D. W. FAHEY, J. M. GILLIGAN, G.
S. DUTTON, T. J. BARING, C. M. VOLK, R. E. DUNN, R. C. MYERS, S. A. MONTZKA, P. R.
WAMSLEY, A. H. HAYDEN, J. H. BUTLER, T. M. THOMPSON, T. H. SWANSON, E. J. DLUGOKENCKY, P.
C. NOVELLI, D. F. HURST, J. M. LOBERT, S. J. CICIORA, R. J. MCLAUGHLIN, T. L. THOMPSON, R.
H. WINKLER, P. J. Fraser, L. P. Steele, M. P. Lucarelli. Airborne gas chromatograph for
in situ measurements of long-lived species in the upper troposphere and lower
stratosphere. Geophys. Res. Lett. 23, 347-350 (1996).
A new instrument, the Airborne Chromatograph for Atmospheric Trace Species IV (ACATS-IV), for measuring
long-lived species in the upper troposphere and lower stratosphere is described. Using an
advanced approach to gas chromatography and electron capture detection, the instrument can
detect low levels of CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2F-CClF2), methyl chloroform (CH3CCl3), carbon tetrachloride (CCl4), nitrous oxide (N2O), sulfur
hexafluoride (SF6), Halon-1211 (CBrClF2), hydrogen (H2), and methane
(CH4) acquired in ambient samples every 180 or 360 s.
The instrument operates fully-automated onboard the NASA ER-2 high-altitude aircraft on
flights lasting up to 8 hours or more in duration. Recent measurements include 24
successful flights covering a broad latitude range (70°S-61°N) during the Airborne
Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of
Stratospheric Aircraft (ASHOE/MAESA) campaign in 1994.
HATS-96-003
- S.A. MONTZKA, R.C. MYERS, J.H. BUTLER, J.W.
ELKINS, L.T. LOCK, A.D. CLARKE, and A.H. GOLDSTEIN. Observations of HFC-134a in the
remote troposphere Geophys. Res. Lett. 23, 169-172 (1996).
Hydrofluorocarbon-134a (CF3CH2F)
has been detected and quantified in air samples collected at remote, globally dispersed
locations. Using gas chromatography and mass spectrometry detection techniques, we have
observed increases for HFC-134a throughout the global troposphere from <50 fmol mol-1 (ppq) in the late 1980s to 1.6 pmol mol-1
(ppt) in mid-1995. Results obtained from samples collected during two cruises in 1994
indicate that mixing ratios more than doubled during that year. Increases observed
globally from early 1994 through mid-1995 are consistent with exponential growth at ~100%
yr-1.
HATS-96-004 (available
online, click identifier on left)
- J.M. LOBERT, J.H. BUTLER, L.S. GELLER, S.A.
YVON, S.A. MONTZKA, R.C. MYERS, A.D. CLARKE, AND J.W. ELKINS. BLAST 94: Bromine
Latitudinal Air Sea Transect 1994. Report on Oceanic Measurements of Methyl Bromide and
Other Compounds. NOAA Technical Memorandum ERL CMDL-10 (2/1996). Available from NTIS,
5285 Port Royal Road, Springfield, VA 22161 USA.
The Halocarbons and other Atmospheric Trace Species (HATS) division of NOAA/CMDL
participated in two research cruises in 1994 for the Bromine Latitudinal Air/Sea
Transect project. Frequently collected CH3Br data
from these expeditions constitute the largest data set for oceanic CH3Br
to date, and the first solid estimate of oceanic emission, production and degradation of
the compound. Our conclusion from these studies is that the ocean is probably not a net
source of CH3Br, but rather a net sink. Although CH3Br is both produced and consumed everywhere in the surface ocean,
the rate of consumption exceeds that of production in most waters sampled. Exceptions were
coastal and coastally influenced waters, which were typically supersaturated, and areas of
open ocean upwelling, where CH3Br saturations were close
to zero. About 80% of the oceans are undersaturated in CH3Br,
representing a net annual sink of 8-22 Gg y-1.
In addition to conducting two research cruises, we investigated potential contamination
effects from sampling flasks and potential analytical artifacts from GC/ECD systems,
developed a calibration scale for atmospheric and oceanic CH3Br
and a global, finite-increment model for more precisely estimating the partial lifetime of
atmospheric CH3Br with respect to oceanic losses.
CH3Br data from the second cruise indicate that our
conclusions from the first expedition were qualitatively and quantitatively accurate. The
latter results give greater strength to the global extrapolations of the first data set.
Our best estimate of the partial lifetime of atmospheric CH3Br
with respect to oceanic losses is 2.7 (2.4-6.5) y. This range was derived from a 40 year,
global data set of sea surface temperatures and windspeeds. Data from the two expeditions
suggest a shorter lifetime of CH3Br on the order of 2.4
y. The difference between the two estimates is due to the high windspeeds encountered
during the cruises. Our estimate of the atmospheric lifetime, based upon combined
atmospheric and oceanic losses, is now 1.0-1.1 y, compared to earlier estimates of
1.8-2.1 y when the ocean was considered an insignificant sink and tropospheric OH
concentrations were underestimated by 15%. The oceanic sink correspondingly lowers the ODP
for CH3Br by about one-third.
Work on the sampling and analytical uncertainties has revealed significant problems with
the measurement of CH3Br in flasks, which have been used
historically for virtually all previous measurements of CH3Br
in the atmosphere. Whereas results from the shipboard system were free of sample storage
effects and both the shipboard and the laboratory-based GC/MS systems were free of
problems with co-eluting compounds, our results in analyzing flasks from the first
expedition show that CH3Br in flasks often is unstable
and will increase or decrease with time. In addition, we found that results for CH3Br determined by GC/ECD can be compromised by some GC
configurations.
HATS-96-005
- J.H. BUTLER Scientific uncertainties in
the budget of atmospheric methyl bromide. Atmos. Environ., 30, i-iii,
1996.
No abstract
HATS-96-006
- Minschwaner, K., A.E. Dessler, J.W. ELKINS,
C.M. VOLK, D.W. Fahey, M. Loewenstein, J.R. Podolske, A.E. Roche, and K.R. Chan. Bulk
properties of isentropic mising into the tropics in the lower stratosphere. J. Geophys.
Res. 101D, 9433-9439 (1996).
Timescales for mixing of midlatitude air into the tropical lower stratosphere are deduced
from observations of long-lived tracers N2O and CCl3F. Bulk mixing between tropical and midlatitude regions is assumed
to be isentropic and relatively slow compared with local mixing within each region. The
mean value of the mixing timescale ranges from 12 to 18 months near 20 km. There is a
tendency for shorter mixing times at higher and lower altitudes, although vertical
profiles of mixing cannot be definitively established by the data. A more robust quantity
is given by the fraction of midlatitude air entrained into the tropical upwelling region.
Implied mixing fractions exceed 50% above 22 km.
HATS-96-007
- S.A. YVON, and E.S. Saltzman. Atmospheric
sulfur cycling in the tropical Pacific marine boundary layer (12°S, 135°W): A comparison
of field data and model results 2. Sulfur dioxide. J. Geophys. Res. 101D,
6911-6918 (1996).
The atmospheric chemistry of sulfur dioxide over the tropical South Pacific Ocean is
investigated by using results from field measurements and numerical models. Simultaneous
real time measurements of sulfur dioxide and its biogenic precursor dimethylsulfide were
made at 12°S, 135°W for a 6-day period from March 3 through March 9, 1992. The mean SO2
and DMS mole fractions were 71±56 pmol mol-1 and 453±93 pmol mol-1,
respectively. These concentrations are compared to those predicted by a time-dependent
photochemical box model of the marine boundary layer. Model estimates of the yield of SO2
from DMS oxidation range from 27% to 54%. Even with low yields, DMS is the dominant source
of SO2 in this region. Estimates of vertical entrainment velocities based on
the tropospheric ozone budget suggest that vertical entrainment is a minor source of SO2.
The relative rates of various loss mechanisms for SO2 are dry deposition to the
sea surface (58%), in-cloud oxidation (9%), OH oxidation (5%), and uptake by sea-salt
aerosols (28%).
HATS-96-008
- S.A. YVON, E.S. Saltzman, D.J. Cooper, T.S.
Bates, and A.M. Thompson. Atmospheric sulfur cycling in the tropical Pacific marine
boundary layer (12°S, 135°W): A comparison of field data and model results 1.
Dimethylsulfide. J. Geophys. Res. 101D, 6899-6909 (1996).
Shipboard measurements of atmospheric and seawater DMS were made at 12°S, 135°W for 6
days during March 1992. The mean seawater DMS concentration during this period was
4.1±0.45 nM (1, n = 260) and mean atmospheric DMS mole fraction was 453±93 pmol mol-1
(1 n = 843). Consistent atmospheric diel cycles were observed, with a nighttime maximum
and daytime minimum and an amplitude of approximately 85 pmol mol-1.
Photochemical box model calculations were made to test the sensitivity of atmospheric DMS
concentrations to the following parameters: 1) sea-to-air flux, 2) boundary layer height,
3) oxidation rate, and 4) vertical entrainment velocities. The observed relationship
between the mean oceanic and atmospheric DMS levels require the use of an air-sea exchange
coefficient which is at the upper limit end of the range of commonly used
parameterizations. The amplitude of the diel cycle in atmospheric DMS is significantly
larger than that predicted by a photochemical model. This suggests that the sea-to-air DMS
flux is higher than was previously thought, and the rate of daytime oxidation of DMS is
substantially underestimated by current photochemical models of DMS oxidation.
HATS-96-009
- S.A. YVON, J.M.C. Plane, C.-F. Nien, D.J.
Cooper, and E.S. Saltzman. Interaction between nitrogen and sulfur cycles in the polluted
marine boundary layer. J. Geophys. Res. 101D, 1379-1386 (1996).
Simultaneous measurements are reported of the nitrate radical (NO3), nitrogen
dioxide (NO2), ozone (O3), and dimethylsulfide (DMS) in the
nighttime marine boundary layer over Biscayne Bay in South Florida. These field
observations are analyzed and used to initialize a boundary layer box model which examines
the relative importance of the various sinks for Nox in the marine boundary layer. The
results show that the observed lifetime of NO3 (6 min.) is probably controlled
both by the loss of nitrogen pentoxide (N2O5) to reaction with water
vapor and aerosols and by the reaction between NO3 and DMS. The model is then
extended to investigate the loss of nitrogen oxides from an air parcel that remains in the
boundary layer with a constant sea-to-air DMS flux for several days. The principal
conclusions are (1) that DMS is a much more important sink for NO3 at lower NO2
levels and (2) that the reaction between NO3 and DMS is an important sink for
DMS in the marine boundary layer and could exceed that of the daytime removal by OH.
HATS-96-010 (more information available online, click identifier on left)
- S. A. MONTZKA, J.H. BUTLER, R.C. MYERS, T.M.
THOMPSON, T.H. SWANSON, A.D. CLARKE, L.T. LOCK, and J.W. ELKINS. A decline in the
tropospheric abundance of halogen from halocarbons: Implications for stratospheric ozone
depletion. Science 272, 1318-1322, (1996).
Analyses of air sampled from remote locations across the globe reveal that tropospheric
chlorine attributable to anthropogenic halocarbons peaked near the beginning of 1994 and
was decreasing at a rate of 25 ± 5 parts per trillion per year by mid 1995. Although
bromine from halons was still increasing in mid-1995, the summed abundance of these
halogens in the troposphere is decreasing. To assess the effect of this trend on
stratospheric ozone, estimates of the future stratospheric abundance of ozone-depleting
gases were made for midlatitude and polar regions on the basis of these tropospheric
measurements. These results suggest that reactive chlorine and bromine will reach a
maximum in the stratosphere between 1997 and 1999 and will decline thereafter if limits
outlined in the adjusted and amended Montreal Protocol on Substances That Deplete the
Ozone Layer are not exceeded in future years.
1995
HATS-95-001
- Dessler, A.E., E.M. Weinstock, E.J. Hintsa, J.G. Anderson, C.R. Webster, R.D. May, J.W. ELKINS , and G.S. DUTTON. An examination
of the total hydrogen budget of the lower stratosphere. Geophysical Research
Letters 21(23), 2563-2566 (1994).
We analyze the hydrogen budget of the lower stratosphere using simultaneous in situ
measurements of northern hemispheric water vapor (H2O)
and methane (CH4) obtained during the spring
Stratospheric Photochemistry, Aerosols, and Dynamics Expedition (SPADE), as well as
previously published in situ H2 data. Based on this
data, we conclude that approximately two H2O molecules
are produced for each CH4 molecule destroyed. This
implies that H2 production from CH4
oxidation is balanced by H2 oxidation. The uncertainty
in this analysis is greatly reduced by the use of multiple data sets. Additionally, we
infer that, on an annual and global average, H2O enters
the stratosphere with a mixing ratio of 4.2 0.5 ppmv, and that the quasi-conserved
quantity 2 [CH4] + [H2O]
has a value of 7.6±0.6 ppmv in these northern hemisphere air parcels (where [x]
denotes the mixing ratio of the constituent x).
HATS-95-002
- LOBERT, J.M. , J.H. BUTLER, S.A. MONTZKA, L.S.
GELLER, R.C. MYERS,and J.W. ELKINS. A net sink for atmospheric CH3Br
in the EastPacific Ocean. Science 267, 1002-1005 (1995).
Surface waters along a cruise track in the East Pacific Ocean were undersaturated in
methyl bromide (CH3Br) in most areas except for coastal
and upwelling regions, with saturation anomalies ranging from +100 percent in coastal
waters to -50 percent in open ocean areas, representing a regionally weighted mean of -16
(-13 to-20) percent. The partial lifetime of atmospheric CH3Br
with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6)
years. The global, mean dry mole fraction of CH3Br in
the atmosphere was 9.8 0.6 parts per trillion, with an interhemispheric ratio of 1.31
0.08. These data indicate that ~8 percent (0.2 parts per trillion) of the observed
interhemispheric difference in atmospheric CH3Br could
be attributed to an uneven global distribution of oceanic sources and sinks.
HATS-95-003
- MONTZKA, S.A. , R.C. MYERS, J.H. BUTLER, and
J.W. ELKINS. Early trends in the global tropospheric abundance of
hydrochlorofluorocarbon-141b and 142b. Geophysical Research Letters 21(23),
2483-2486 (1994).
Hydrochlorofluorocarbons (HCFCs) are rapidly replacing chlorofluorocarbons(CFCs) as
foam-blowing agents, solvents, and refrigerants. These substitutes, however, still contain
chlorine and have the potential to deplete stratospheric ozone. Although the ozone
destruction capacity of HCFCs is believed to be significantly less than that for CFCs,
concern over unrestricted chlorine input to the atmosphere from HCFC use has prompted
proposals for future limits on production. Here we report the first global time-series for
mixing ratiosof HCFC-141b (1,1-dichloro-1-fluoroethane) and HCFC-142
(1-chloro-1,1-difluoroethane) in air collected at seven remote sampling stations. Global
mean mixing ratios in mid-1993 were 0.7 parts per trillion (ppt) for HCFC-141b and 4.3 ppt
for HCFC-142b. The global atmospheric abundance of HCFC-141b increased by 0.9 ppt, or a
factor of ~3, in 1993. Global abundance of HCFC-142b increased by 1.1 ppt/yr during
1992-1993. The results suggest that HCFCs are currently used extensively for replacing
CFCs in selected applications. Furthermore, measured levels are significantly higher than
expected based on available emission estimates and consumption predictions.
HATS-95-004
- Salawitch, R.J., S.C. Wofsy, P.O. Wennberg, R.C. Cohen, J.G. Anderson, D.W. FAHEY, R.S.
GAO, E.R. KEIM, E.L. WOODBRIDGE, R.M. Stimpfle, J.P. Koplow, D.W. Kohn, C.R. Webster, R.D.
May, L. Pfister, E.W. Gottlieb, H.A. Michelsen, G.K. Yue, J.C. Wilson, C.A. Brock, H.H.
Jonsson, J.E. Dye, D. Baumgardner, M.H PROFFITT, M. Loewenstein, J.R. Podolske, J.W. ELKINS , G.S. DUTTON, E.J. Hintsa, A.E.
Dessler, E.M. Weinstock, K.K. KELLY, K.A. Boering, B.C. Daube, K.R. Chan, and S.W. Bowen. The
distribution of hydrogen, nitrogen, and chlorine radicals in the lower stratosphere,
Implications for changes in O3 due to emission of NOy
from supersonic aircraft. Geophysical Research Letters 21(23), 2547-2550
(1994).
In situ measurements of hydrogen, nitrogen, and chlorine radicals obtained in the lower
stratosphere during SPADE are compared to results from a photochemical model that
assimilates measurements of radical precursors and environmental conditions. Models
allowing for heterogeneous hydrolysis of N2O5 agree well with measured concentrations of NO and ClO, but
concentrations of HO3 and OH are underestimated by 10 to
25%, concentrations of NO2 are overestimated by 10 to
30%, and concentrations of HCl are overestimated by a factor of 2. Discrepancies for [OH]
and [HO2] are reduced if we allow for higher yields of
O(1D) from O3 photolysis and for
heterogeneous production of HNO2. The data suggest more
efficient catalytic removal of O3 by hydrogen and
halogen radicals relative to nitrogen oxide radicals than predicted by models using
recommended rates and cross sections. Increases in [O3]
in the lower stratosphere may be larger in response to inputs of NOy from supersonic
aircraft than estimated by current assessment models.
HATS-95-005
- TUCK, A.F., D.W. FAHEY, M. Lowenstein, J.R. Podolske, K.K. KELLY, S.J. HOVDE, D.M.
MURPHY, and J.W. ELKINS . Spread of
denitrification from 1987 Antarctic and 1988-1989 Arctic stratospheric vortices. Journal
of Geophysical Research 99(D10), 20,573-20,583 (1994).
Vertical profiles of N2O and NOy taken by the ER-2
outside the vortex are used to construct average vertical profiles of F(NOy) = NOy/(A-N2O), where A is the tropospheric content of N2O
three years prior to the measurements. The southern hemisphere has less nitrous oxide in
the range 400 < THETA < 470K, by up to 25% relative to the northern hemisphere.
F(NOy) is the ratio of NOy produced to N2O lost in a
stratospheric air mass since entry from the troposphere. The profiles of F(NOy) have the
following characteristics, (1) Relative to 1991-1992, a year without denitrification
inside or outside the vortex, the northern hemisphere in 1988-1989 showed denitrification
outside the vortex ranging up to 25% and averaging 17% above THETA = 425 K. (2) Relative
to the northern hemisphere in 1991-1992, the southern hemisphere in 1987 showed
denitrification outside the vortex ranging up to 32% and averaging 20% above THETA = 400
K. (3) Below THETA = 400 K the southern hemisphere showed enhancements of F(NOy) relative
to the northern hemisphere in 1991-1992 ranging up to 200% at THETA = 375 K, outside the
vortex. Corresponding profiles of residual water, R(H2O)
= H2O - 2 [1 · 6 - CH4],
are considered and shown to be consistent with those of F(NOy) in the sense that they show
deficits outside the Antarctic vortex, which was both dehydrated and denitrified, but not
outside the 1988-1989 Arctic vortex, which was denitrified but not dehydrated. R(H2O) is the water content of stratospheric air with the contribution
from methane oxidation subtracted. Comparison of F(NOy) and R(H2O)
below 400 K outside the Antarctic vortex leads to the suggestion that dehydration in the
Antarctic vortex occurs by the sedimentation of ice crystals large enough to fall out of
the stratosphere, whereas denitrification occurs mainly on mixed nitric acid-water
crystals which evaporate below the base of the vortex at THETA = 400 K but above the
tropopause.
HATS-95-006
- Waugh, D.W., R.A. Plumb, P.A. Newman, M.R. Schoeberl, L.R. Lait, M. Loewenstein, J.R.
Podolske, J.W. ELKINS, and K.R. Chan. Fine-scale,
poleward transport of tropical air during AASE 2. Geophysical Research Letters
21(23), 2603-2606 (1994).
The poleward transport of tropical air in the lower stratosphere during the winter period
of the second Airborne Arctic Stratospheric Expedition (December 1991-March 1992) is
examined using contour advection calculations. These calculations show that filaments of
tropical air extend into midlatitudes and are wrapped around the equatorward edge of the
polar jet. Simultaneously, filaments are drawn from the polar vortex and are intermingled
with the filaments of tropical air. The tropical filaments are consistent with
measurements of chemical tracers taken aboard the ER-2 and DC-8 aircraft which show
localized regions, in midlatitudes, of air with the characteristics of tropical air.
HATS-95-007
- Wofsy, S.C., K.A. Boering, B.C. Daube, Jr., M.B. McElroy, M. Loewenstein, J.R. Podolske,
J.W. ELKINS , G.S. DUTTON, and D.W. FAHEY. Vertical
transport rates in the stratosphere in 1993 from observations of CO2, N2O , and CH4. Geophysical
Research Letters 21(23), 2571-2574 (1994).
Measurements of CO2, N2O,
and CH4 are analyzed to define hemispheric average
vertical exchange rates in the lower stratosphere from November 1992 to October 1993.
Effective vertical diffusion coefficients were small in summer, <1 m2/s at
altitudes below 25 km; values were similar near the tropopause in winter, but increased
markedly with altitude. The analysis suggests possibly longer residence times for exhaust
from stratospheric aircraft, and more efficient transport from 20 km to the middle
stratosphere, than predicted by many current models. Seasonally-resolved measurements of
stratospheric CO2 and N2O
provide significant new constraints on rates for global-scale vertical transport.
HATS-95-008 (available
online, click identifier on left)
- WOODBRIDGE, E.L., J.W. ELKINS, D.W. FAHEY,
L.E. Heidt, S. SOLOMON, T.J. BARING, T.M. GILPIN, W.H. Pollock, S.M. Schauffler, E.L.
Atlas, M. Lowenstein, J.R. Podolske, C.R. Webster, R.D. May, J.M. GILLIGAN, S.A. MONTZKA,
K.A. Boering, and R.J. Salawitch. Estimates of total organic and inorganic chlorine in
the lower stratosphere from in situ and flask measurements during AASE II. Journal
of Geophysical Research 100(D2), 3057-3064 (1995).
Aircraft sampling has provided extensive in situ and flask measurements of organic
chlorine species in the lower stratosphere. The recent Airborne Arctic Stratospheric
Expedition II (AASE II) included two independent measurements of organic chlorine species
using whole air sample and real-time techniques. From the whole air sample measurements we
derive directly the burden of total organic chlorine (CCly) in the lower stratosphere.
From the more limited real-time measurements we estimate the CCly burden using mixing
ratios and growth rates of the principal CCly species in the troposphere in conjunction
with results from a two-dimensional photochemical model. Since stratospheric chlorine is
tropospheric in origin and tropospheric mixing ratios are increasing, it is necessary to
establish the average age of a stratospheric air parcel to assess its total chlorine (ClTotal) abundance. Total inorganic chlorine (Cly) in the parcel is
then estimated by the simple difference, Cly = ClTotal -
CCly. The consistency of the results from these two quite different techniques suggests
that we can determine the CCly and Cly in the lower stratosphere with confidence. Such
estimates of organic and inorganic chlorine are crucial in evaluating the photochemistry
controlling chlorine partitioning and hence ozone loss processes in the lower
stratosphere.
HATS-95-009
- Bertman, S.B., J.M. Roberts, D.D. Parrish, M.P. Buhr, P.D. Goldan, W.C. Kuster, F.C.
Fehsenfeld, S.A. MONTZKA, and H. Westberg. Evolution
of alkyl nitrates with air mass age. Journal of Geophysical Research
100(D11):22,805-22,813 (1995).
Alkyl nitrates (RONO2) and alkanes (RH) were measured at
Scotia, Pennsylvania, in 1988 and at the Kinterbish Wildlife Area, Alabama, in 1992. A
simple kinetic analysis was developed to relate the two species' concentrations based on
the analytical solution of two sequential first-order reactions using OH chemistry, RONO2 photolysis, and assuming peroxy radicals (ROO) + NO as the source
of RONO2. The analysis predicts an increase in RONO2/RH
ratio with time. The C4 and C5
secondary alkyl nitrate/alkane ratios vary in a manner consistent with ROO + NO chemistry
as their only source and photolysis and OH reaction as their only sinks. Comparison of
ambient measurements of these compounds with predictions indicate that measured air masses
experienced photochemical processing times consistent with alkyl nitrate evolution times
between 0.1 and 5 days. The relationships of ethyl nitrate, n-propyl nitrate and 2-propyl
nitrate ratios to their parent alkanes all indicate additional sources of RONO2, probably of a photochemical nature. Decomposition of larger
alkoxy radicals are discussed as one possible source of smaller ROO radicals.
HATS-95-010
- Buhr, M., D. Parrish, J. Elliot, J. Holloway, J. Carpenter, P. Goldan, W. Kuster, M.
Trainer, S. MONTZKA, S. McKeen, and F.
Fehsenfeld. Evaluation of ozone precursor source types using principal component
analysis of ambient air measurements in rural Alabama. Journal of Geophysical
Research 100(D11):22,853-22,860 (1995).
The sources of photochemical precursors for ozone, primarily NOx (NO + NO2) and reduced carbon (CO and hydrocarbons), were evaluated using
principal component analysis (PCA) of concurrent measurements of [NOx],
[NOy] (total reactive oxidized nitrogen species), [CO],
[SO2], [C3H8], [C6H6],
and [O3] collected at a rural Alabama field site during
the summers of 1990 and 1992. Two separate data matrices were analyzed, including a low
measurement frequency matrix that included all of the variables and a high measurement
frequency matrix that included all of the variables except for the hydrocarbons. The
results of the PCA indicated that the major sources of NOy
in the region are (1) coal-fired power plants and (2) biomass burning and/or paper mills.
The identifications are based on the [CO]/[NOy] and [SO2]/[NOy] emission ratios derived
from the measurements in comparison with the expected emission ratios that are based upon
the National Acid Precipitation Assessment Program (NAPAP) emission inventory and upon
laboratory experiments. The results indicated that the NAPAP inventory, integrated over
the southeastern region of the United States, may overestimate the current [SO2]/[NOy] emission ratio from
coal-fired power plants and may underestimate the [CO]/[NOy]
emission ratio from paper mills. The results also suggest that biomass burning in the
southeastern United States may be an important component in the NOy inventory, both as a
point source associated with paper mills and as a seasonally dependent area source. The
variation of [O3] observed at the site was primarily
related to the variation of [NOy].
HATS-95-011
- BUTLER, J.H. Methyl bromide under
scrutiny. Nature 376:469-470 (1995).
No abstract.
HATS-95-012
- Goldan, P.D., W. C. Kuster, F.C. Fehsenfeld, S.A.
MONTZKA. Hydrocarbon measurements in the southeastern United States: The Rural
Oxidants in the Southern Environment (ROSE) Program 1990. Journal of Geophysical
Research 100(D12):25,945-25,963 (1995).
An automated gas chromatographic system was employed at a rural site in western central
Alabama to measure atmospheric hydrocarbons and oxygenated hydrocarbons (oxy-hydrocarbons)
on an hourly basis from June 8 to July 19, 1990. The location, which was a designated site
for the Southern Oxidant Study (SOS), was instrumented for a wide variety of measurements
allowing the hydrocarbon and oxy-hydrocarbon measurements to be interpreted both in terms
of meteorological data and as part of a large suite of gas phase measurements. Although
the site is situated in a Loblolly pine plantation, isoprene was observed to be the
dominant hydrocarbon during the daytime with afternoon maxima of about 7 parts per billion
by volume (ppbv). Decrease of isoprene after sunset was too rapid to be accounted for
solely on the basis of gas phase chemistry. During the nighttime, -pinene and -pinene were
the dominant hydrocarbons of natural origin. The ratio of -pinene to -pinene showed a
well-defined diurnal pattern, decreasing by more than 30% during the night; a decrease
that could be understood on the basis of local gas phase chemistry. Oxy-hydrocarbons,
dominated by methanol and acetone, were the most abundant compounds observed. On a carbon
atom basis, the oxy-hydrocarbons contributed about 46% of the measured atmospheric burden
during the daytime and about 40% at night. The similarity of the observed diurnal methanol
variation to that of isoprene and subsequent measurements [McDonald and Fall, 1993]
indicate that much of the observed methanol was of local biogenic origin. Correlation of
acetone with methanol suggests that it, also, has a significant biogenic source. In spite
of the site's rural location, anthropogenic hydrocarbons constituted, on a carbon atom
basis, about 21% of the hydrocarbon burden measured during the daytime and about 55% at
night. Significant diurnal variations of the anthropogenic hydrocarbons, with increases at
night, appeared to be driven by the frequent formation of a shallow nocturnal boundary
layer.
HATS-95-013
- Helas, G., J. LOBERT, D. Scharffe, L. Schafer,
J. Goldammer, J. Baudet, B. Ahoua, A.-L. Ajavon, J.-P. Lacaux, R. Delmas, and M.O.
Andreae. Ozone production due to emissions from vegetation burning. Journal of
Atmospheric Chemistry 22:163-174 (1995).
Ozone has been observed in elevated concentrations by satellites over areas previously
believed to be "background". There is meteorological evidence, that these ozone
"plumes" found over the Atlantic Ocean originate from vegetation fires on the
African continent. In a previous study (DECAFE-88), we have investigated ozone and assumed
precursor compounds over African tropical forest regions. Our measurements revealed large
photosmog layers at altitudes from 1.5 to 4 km. Both chemical and meteorological evidence
point to savanna fires up to several thousand km upwind as sources. Here we describe ozone
mixing ratios observed over western Africa and compare ozone production ratios from
different field measurement campaigns related to vegetation burning. We find that air
masses containing photosmog "ingredients" require several days to develop their
oxidation potential, similar to what is known from air polluted by emissions from fossil
fuel burning. Finally, we estimate the global ozone production due to vegetation fires and
conclude that this source is comparable in strength to the stratospheric input.
HATS-95-014 (available
online, click identifier on left)
- LOBERT, J.M., J.H. BUTLER, T.J. BARING, S.M.
MONTZKA, R.C. MYERS, and J.W. ELKINS. OAXTC 92: Ocean/Atmosphere Exchange of Trace
Compounds 1992: Oceanic measurements of HCFC-22, CFC-11, CFC-12, CFC-113, CH3CCl3, CCl4,
and N2O in the marine air and surface waters of the west
Pacific Ocean (August 3-October 21, 1992). NOAA Technical Memorandum ERL CMDL-9,
43 pp. (1995).
CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2FCClF2), methyl chloroform (CH3CCl3), carbon tetrachloride (CCl4),
nitrous oxide (N2O) and HCFC-22 (CHCIF2) were measured in the air and surface waters of the Pacific Ocean
between 55N and 22S during the later summer and early fall of 1992. Atmospheric
measurements of all gases agreed well with results from NOAA fixed stations at similar
latitudes. CFC-11, CFC-12, and CFC-113, which have long atmospheric lifetimes and are
essentially inert in seawater, responded mainly to physical processes in the air and
water. The first two gases were supersaturated by 2-6% at higher, northern latitudes,
reflecting the effects of radiative warming. Their saturation anomalies declined southward
through the tropics and ultimately became slightly negative in the southern hemisphere.
HCFC-22 showed signs of small losses in the tropics and subtropics, a sink that may
account for 2% of the losses of this gas from the atmosphere. CH3CCl3 showed a similar
pattern, with only a tropical sink, which is consistent with hydrolysis and, together with
data from an earlier expedition, implies that about 6% of atmospheric CH3CCl3 is lost to the ocean. The
net saturation anomaly for CCl4 was virtually negative
everywhere and only slightly dependent upon latitude. This would be expected for a sink
that was not particularly temperature dependent and it is consistent with evidence from
deepwater profiles that indicate a sink at depth. Fluxes calculated from CCl4 saturation anomalies indicate that 15-35% of atmospheric CCl4 is lost to the ocean. N2O
surface water data indicated weak equatorial upwelling. Saturation anomalies ranged from
1-6%, which would be consistent with a small source in the W. Pacific.
HATS-95-015
- MONTZKA, S.A., M. TRAINER, W.M. ANGEVINE,
and F.C. FEHSENFELD. Measurements of 3-methyl furan, methyl vinyl ketone, and
methacrolein at a rural forested site in the southeastern United States. Journal of
Geophysical Research 100(D6):11,393-11,401 (1995).
Three oxygenated hydrocarbons were measured in ambient air above a rural forested site in
western Alabama. Mixing ratios of methyl vinyl ketone (MVK), methacrolein (MACR), and
3-methyl furan were determined during a 3-week period in the summer of 1992. While the
mean mixing ratio for methyl vinyl ketone was determined to be 740 parts per 10-12
(ppt), the mean mixing ratio for methacrolein was 480 ppt. The results for methyl vinyl
ketone and methacrolein are compared to previously reported measurements from this same
location during the summer of 1990. Although isoprene levels were lower by ~50% in 1992,
mixing ratios of the carbonyls were reduced by only ~25%. These differences are discussed
in light of the changes that had occurred in the forest canopy in the time elapsed between
the two measurement campaigns. Despite the differences observed during the 2 years, a
consistent diurnal variability is observed for methyl vinyl ketone, relative to
methacrolein, during both years. In addition to a weak correlation observed between the
carbonyls and temperature, levels of MVK and MACR in air sampled from just above the
forest canopy are influenced by the depth of the mixed layer. A third oxidation product of
isoprene, 3-methyl furan, was identified and measured in ambient air. Mean daytime mixing
ratios were estimated at 60 ppt. Nighttime levels were lower, averaging 40 ppt. Mixing
ratios of 3-methyl furan were highly correlated with isoprene (R2 - 0.82), and during the
day, were typically ~2% of levels measured for isoprene.
1994
HATS-94-001
- BUTLER, J.H. The potential role of the
ocean in regulating atmospheric CH3Br. Geophysical
Research Letters 21(3), 185-188 (1994).
An increase or decrease in anthropogenic emissions of methyl bromide (CH3Br) will induce a compensating flux of this gas from the ocean to
the atmosphere. This, in turn, will tend to lessen the expected change in atmospheric
mixing ratio from that calculated in models that incorporate a constant oceanic source. To
a first degree, this buffering effect by the ocean is independent of in situ oceanic
production and land based sources. The partial lifetime of atmospheric CH3Br with respect to the ocean could reasonably range from 1.3 to 14
y, with a current best estimate of 3.7 y. This yields an effective atmospheric lifetime,
which incorporates oceanic losses and thus can be used in simple, mass balance
calculations of atmospheric CH3Br, of 1.2 y, with a
probably range of 0.7 to 1.8 y.
HATS-94-002
- BUTLER, J.H., J.W. ELKINS, B.D. HALL, S.A.
MONTZKA, S.O. CUMMINGS, P.J. Fraser, and L.W. Porter. Recent trends in the global
atmospheric mixing ratios of Halon-1301 and Halon -1211. Baseline Atmospheric
Program Australia 1991, A.L. Dick and J.L. Gras (eds.). Department of the Environment,
Sport, and Territories Bureau of Meteorology in cooperation with CSIRO Division of
Atmospheric Research, Melbourne, Australia, 29-35 (1994).
No abstract.
HATS-94-003
- HURST, D.F., D.W.T. Griffith, and G.D.Cook. Trace
gas emissions from biomass burning in tropical Australian savannas. Journal of
Geophysical Research 99(D8), 16,441-16,456 (1994).
During the 1991 and 1992 dry seasons (April to October), we collected and analyzed over
100 samples of smoke from savanna fires at the Kapalga Research Station (12S, 132E) in
Kakadu National Park, Northern Territory, Australia. Samples collected from the ground and
from a light aircraft flying at 50-700 m above the fires were analyzed for CO2, CO, CH4, C2H2, C6H6,
CH2O, CH3CHO, NOX (=NO+NO2), NH3, HCN, and CH3CN using gas phase
Fourier transform infrared (FTIR) spectroscopy, matrix isolation FTIR spectroscopy, and
chemiluminescence techniques. In addition, we made detailed analyses of the mass, carbon,
and nitrogen loads of the prefire fuel and the postfire ash residue. Molar emission ratios
relative to emitted CO2 and CO, and emission factors
relative to the fuel carbon or nitrogen burned were determined for the measured trace
gases Over 96% of the fuel carbon burned was released to the atmosphere, predominantly as
CO2 (87±3% of fuel C) and CO (7.8±2.3%). The mean
CO/CO2 emission ratio of 9.0 2.6% indicates efficient
combustion in these fires of grasses and other light fuels. The main nitrogen-based
emissions we measured were NOX (21±8% of fuel N) and NH3 (23±13%). The combined emissions of NOX,
NH3, N2O, CH3CN, and HCN accounted for only 51±17% of the fuel N released to
the atmosphere during combustion. We use these measurements to estimate the annual
emissions of several important trace gases from savanna burning in Australia.
HATS-94-004
- MONTZKA, S.A., R.C. MYERS, J.H. BUTLER, J.W.
ELKINS, and S.O. CUMMINGS. Atmospheric measurements of HCFC-22 at the South Pole. Antarctic
Journal 28(5), 267-269 (1994).
No abstract.
HATS-94-005
- MONTZKA, S.A., M.R. NOWICK, R.C. MYERS, J.W.
ELKINS, J.H. BUTLER, S.O. CUMMINGS, P.J. Fraser, and L.W. Porter. NOAA-CMDL
chlorodifluoromethane (HCFC-22) observations at Cape Grim. Baseline Atmospheric
Program Australia 1991, A.L. Dick and J.L. Gras (eds.). Department of the Environment,
Sport, and Territories Bureau of Meteorology in cooperation with CSIRO Division of
Atmospheric Reseach, Melbourne, Australia, 25-28 (1994).
No abstract.
HATS-94-006
- STURGES, W.T. Halocarbons in the Arctic and
Antarctic Atmosphere. In The Tropospheric Chemistry of Ozone in the Polar
Regions, H. Niki, and K.H. Becker (eds.). Springer-Verlag, New York, 117-130 (1993).
No abstract.
HATS-94-007
- STURGES, W.T., J.F. HOPPER, L.A. BARRIE, and
R.C. SCHNELL. Stable lead isotope ratios in Alaskan Arctic aerosols. Atmospheric
Environment 27A(17/18), 2865-2871 (1993).
Aerosol samples collected at Barrow, Alaska, during February and March 1990 were found to
have uniform stable lead isotope compositions. The mean 208Pb/207Pb ratios was 2.423 0.009
and the mean 206Pb/207Pb ratio was 1.161±0.014. The latter ratio is essentially the same
as that obtained from an earlier study of aerosols at two Canadian stations in the High
Arctic and is typical of, but not unique to, Eurasian sources of atmospheric lead. Further
discriminating power was available in this study through the inclusion of 208Pb/207Pb
ratios, which provided additional evidence that the former Soviet Union and eastern Europe
are major contributors to atmospheric particulate lead in the Alaskan Arctic, accounting
for around two-thirds of the particulate lead measured at Barrow. The remaining third of
the lead is attributed to west European sources. There was no evidence for a substantial
North American component, other than local contamination.
HATS-94-008
- STURGES, W.T., R.C. SCHNELL, S. Landsberger,
S.J. OLTMANS, J.M. HARRIS, and S.-M. Li. Chemical and meteorological influences on
surface ozone destruction at Barrow, Alaska, during spring 1989. Atmospheric
Environment 27A(17/18), 2851-2863 (1993).
Surface ozone, particulate bromine and inorganic and organic gaseous bromine species were
measured at Barrow, AK, during March and April 1989 to examine the causes of surface ozone
destruction during the Arctic spring. Satellite images of the Alaskan Arctic taken during
the same period were also studied in conjunction with calculated air mass trajectories to
Barrow to investigate the possible origins of the ozone-depleted air. It was found that
during major ozone depletion events (O3 < 25 ppbv)
concentrations of particulate bromine and the organic brominated gases bromoform and
dibromochloromethane were elevated. Air mass trajectories indicated that the air had
crossed areas of the Arctic Ocean where leads had been observed by satellite. The
transport time from the leads was typically a day or less, suggesting a fast loss
mechanism for ozone. A similarly fast production of particulate bromine was shown by
irradiating ambient nighttime air in a chamber with actinic radiation that approximated
daylight conditions. Such rapid reactions are not in keeping with gas-phase photolysis of
bromoform, but further studies showed evidence for a substantial fraction of organic
bromine in the particulate phase; thus heterogeneous reactions may be important in ozone
destruction.
HATS-94-009
- PROFFITT, M.H., K. AIKIN, J.J. Margitan, M. Loewenstein, J.R. Podolske, A. Weaver, K.R.
Chan, H. Fast, and J.W. ELKINS . Ozone loss
inside the northern polar vortex during the 1991-1992 winter. Science 261,
1150-1154 (1993).
Measurements made in the outer ring of the northern polar vortex from October 1991 through
March 1992 reveal an altitude-dependent change in ozone, with a decrease at the bottom of
the vortex and a substantial increase at the highest altitudes accessible to measurement.
The increase is the result of ozone-rich air entering the vortex, and the decrease
reflects ozone loss accumulated after the descent of the air through high concentrations
of reactive chlorine. The depleted air that is released out of the bottom of the vortex is
sufficient to significantly reduce column ozone at mid-latitudes.
HATS-94-010
- Salawitch, R.J., S.C. Wofsy, E.W. Gottlieb, L.R. Lait, P.A. Newman, M.R. Schoeberl, M.
Loewenstein, J.R. Podolske, S.E. Strahan, M.H. PROFFITT, C.R. Webster, R.D. May, D.W.
FAHEY, D. Baumgardner, J.E. Dye, J.C. Wilson, K.K. KELLY, J.W. ELKINS , K.R. Chan, and J.G. Anderson. Chemical
loss of ozone in the Arctic polar vortex in the winter of 1991-92 Science 261,
1146-1149 (1993).
The in situ measurements of chlorine monoxide, bromine monoxide, and ozone are
extrapolated globally, with the use of meteorological tracers, to infer the loss rates for
ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expedition
II (AASE II) in the winter of 1991-1992. The analysis indicates removal of 15 to 20
percent of ambient ozone because of elevated concentrations of chlorine monoxide and
bromine monoxide. Observations during AASE II define rates of removal of chlorine monoxide
attributable to reaction with nitrogen dioxide (produced by photolysis of nitric acid) and
to production of hydrochloric acid. Ozone loss ceased in March as concentrations of
chlorine monoxide declined. Ozone losses could approach 50 percent if regeneration of
nitrogen dioxide were inhibited by irreversible removal of nitrogen oxides
(denitrification), as presently observed in the Antarctic, or without denitrification if
inorganic chlorine concentrations were to double.
HATS-94-011
- STURGES, W.T., C.W. Sullivan, R.C. SCHNELL,
L.E. Heidt, and W.H. Pollock. Bromoalkane production by Antarctic ice algae. Tellus
45B, 120-126 (1993).
Ice microalgae, collected from the underside of annual sea ice in McMurdo Sound,
Antarctica, were found to contain and release to seawater a number of brominated
hydrocarbons. These included bromoform, dibromomethane, mixed bromochloromethanes, and
methyl bromide. Atmospheric measurements in the McMurdo Sound vicinity revealed the
presence of bromoform and methyl bromide in the lower atmosphere, with lowest
concentrations inland, further indicating that biogenic activity in the Sound is a source
of organic bromine gases to the Antarctic atmosphere. This may have important implications
for boundary layer chemistry in Antarctica. In the Arctic, the presence of bromoform has
been linked to loss of surface ozone in the spring. We report here preliminary evidence
for similar surface ozone loss at McMurdo Station.
HATS-94-012
- Webster, C.R., R.D. May, D.W. Toohey, L.M. Avallone, J.G. Anderson, P. Newman, L.Lait,
M.R. Schoeberl, J.W. ELKINS , and K.R. Chan. Chlorine
chemistry on polar stratospheric cloud particles in the arctic winter. Science
261, 1130-1134 (1993).
Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO)
in the Arctic winter vortex showed large HCl losses, of up to 1 part per billion by volume
(ppbv), which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel
trajectory analysis identified that this conversion of inorganic chlorine occurred at air
temperatures of less than 196 4 Kelvin. High ClO was always accompanied by loss of HCl
mixing ratios equal to 1/2 (ClO +2Cl2O2). These data indicate that the heterogeneous reaction HCl + ClONO2 Cl2 + HNO3
on particles of polar stratospheric clouds establishes the chlorine partitioning, which,
contrary to earlier notions, begins with an excess of ClONO2,
not HCl.
HATS-94-013
- LOBERT, J.M., and D.H. Scharffe. N2O-und CH4-Emissionen aus
Biomasseverbrennung. In EMISSIONEN DER TREIBHAUSGASE DISTICKSTOFFOXID UND METHAN IN
DEUTSCHLAND, M. Schön, R. Walz, G. Angerer, K. Bätcher, E. Böhm, T. Hillenbrand, H.
Hiessl, and J. Reichert (eds.). Erick Schidt Verlag, Berlin, 110-132 (1993).
No abstract.
1993
HATS-93-001
- BUTLER, J.H., J.W. ELKINS, B.D. HALL, S.O.
CUMMINGS, and S.A. MONTZKA. A decrease in the growth rates of atmospheric halon
concentrations. Nature 359, 403-405 (1992).
Halons H-1301 (CBrF3) and H-1211 (CBrClF2) have been introduced into the atmosphere, mainly through use in
fire extinguishers, for almost three decades. Although each is now present in the
troposphere at a concentration of only 2 parts per trillion, these gases have long
atmospheric lifetimes (65-77 y for H1301 and 11-16 y for H-1211) and carry significant
amounts of bromine to the stratosphere, where it can destroy ozone catalytically. For this
reason, the halons have high ozone depletion potentials. The manufacture of both gases is
to be discontinued globally by the year 2000, according to the Montreal Protocol, and
perhaps sooner, as a result of unilateral action by users, manufacturers and producing
countries. Here we present a six-year record of tropospheric halon mixing ratios which
shows that the growth rates of H-1301 and H-1211 have already begun to decrease
substantially. This recent decrease in growth rates is consistent with industry emission
estimates (although these have greater uncertainties), and supports current appraisals of
atmospheric lifetimes. Our results suggest that, even though these halons are relatively
long-lived species, their atmospheric mixing ratios may stabilize or begin to decrease
within the next few years.
HATS-93-002
- CANTRELL, C.A., J.A. LIND, R.E. SHETTER, J.G. CALVERT, P.D. GOLDAN, W. KUSTER, F.C.
FEHSENFELD, S.A. MONTZKA , D.D. PARISH, E.J.
WILLIAMS, M.P. BUHR, H.H. WESTBERG, G. ALLWINE, and R. MARTIN. Peroxy radicals in the
ROSE experiment: Measurement and theory. Journal of Geophysical Research
97(D18), 20,671-20,686 (1992).
The concentration of the HO2-RO2
species measured during July 11, 1990, in the ROSE (Rural Oxidants in the Southern
Environment) study in Alabama are compared to those expected from theory from calculations
based upon detailed hourly measurements of a variety of trace gases including the
hydrocarbons, NO, NO2, carbonyl compounds, CO, PAN
(peroxyacetylnitrate) and calculated jO3 values. The
measurements are also compared with the [HO2] + [RO2] as estimated from deviations from the NO2
+ hv (+O2) NO + O3
photostationary state. Within the error of the measurements all of the data appear to be
in reasonable accord.
HATS-93-003>(available
online, click identifier on left)
- ELKINS, J.W., T.M. THOMPSON, T.H. SWANSON,
J.H. BUTLER, B.D. HALL, S.O. CUMMINGS, D.A. Fisher, and A.G. Raffo. Decrease in the
growth rates of atmospheric chlorofluorocarbons 11 and 12. Nature 364, 780-783
(1993).
The discovery of the Antarctic ozone hole in 1985 led to international efforts to reduce
emissions of ozone-destroying chlorofluorocarbons. These efforts culminated in the
Montreal Protocol and its subsequent amendments, which called for the elimination of CFC
production by 1996. Here we focus on CFC-11 (CCl3F) and
CFC-12 (CCl2F2), which
are used for refrigeration, air conditioning and the production of aerosols and foams, and
which together make up about half of the total abundance of stratospheric organic
chlorine. We report on a significant recent decrease in the atmospheric growth rates of
these two species, based on measurements spanning the past 15 years and latitudes ranging
from 83°N to 90°S. This is consistent with CFC-producers' own estimates of reduced
emissions. If the atmospheric growth rates of these two species continue to slow in line
with predicted changes in industrial emission, global atmospheric mixing ratios will reach
a maximum before the turn of the century, and then begin to decline.
HATS-93-004
- GOLDAN, P.D., W.C. KUSTER, F.C. FEHSENFELD, and S.A.
MONTZKA . The observation of a C5 alcohol emission in a North American pine forest.
Geophysical Research Letters 20(11), 1039-1042 (1993).
During a recent study carried out at an isolated site in the Colorado mountains, a C5
alcohol, 2-methyl-3-buten-2-ol, was found to be the most abundant volatile organic
compound of biogenic origin present in the atmosphere. This finding, if generally
characteristic of the natural chemical species present in the atmosphere in forested
areas, has important implications. First, the presence in large quantities of a reactive
chemical compound at these high levels can signifiantly influence the local atmospheric
chemistry. Secondly, this compound, although previously identified as a pheromone for Ips
typographus (spruce bark beetle), an insect predator responsible for major forest
die-backs in this region, is strongly correlated with isoprene. Since isoprene is known to
be emitted by the local vegetation, the observed 2-methyl-3-buten-2-ol appears also to
have a vegetative rather than etomological source.
HATS-93-005
- Hewitt, C.N., and W.T. STURGES (eds.). Global
Atmospheric Chemical Change. Elsevier, London, 470 pp. (1993).
No abstract.
HATS-93-006
- LOBERT, J.M., and J. Warnatz. Emissions
from the Combustion Process in Vegetation. In Fire in the Environment: The
Ecological Atmospheric, and Climatic Importance of Vegetation Fires, P.J. Crutzen and
J.G. Goldammer (eds.). Wiley, New York, 15-37 (1993).
In this chapter we present a detailed description of the processes involved in vegetation
fires, emphasizing the flaming and smoldering stages of biomass burning. The major factors
influencing the appearance of the single stages are discussed as well as their impact on
emissions from fires. General production patterns, especially the importance of the ratio
of flaming to smoldering combustion, are outlined for several classes of compounds, and
some specific reaction paths that are likely to dominate certain emission formations are
discussed. Finally, we summarize the global estimates of the most important emissions and
propose that the complex nature of vegetation fires be simplified to enable reliable
predictions of the emissions from biomass burning in a global scientific effort.
HATS-93-007
- MONTZKA, S.A., R.C. MYERS, J.H. BUTLER, and
J.W. ELKINS. Global tropospheric distribution and calibration scale of HCFC-22. Geophysical
Research Letters 20(8), 703-706 (1993).
Measurements of atmospheric chlorodifluoromethane (HCFC-22), based upon a new calibration
scale developed in this laboratory, suggest a global tropospheric mean that is ~28% lower
than determined previously from surface-based measurements. A global mean of 101.8 (±1.2,
1 s.d.) ppt and interhemispheric difference of 13 (±1) ppt were determined for HCFC-22 in
1992 from air collected in flasks from seven remote sites located between 82°N and 90°S.
These results are consistent with mixing ratios predicted from recent emission estimates
and a lifetime for HCFC-22 of 13.6 (+1.9, -1.5) yr. Based upon the analysis of flasks and
archived air samples from mid-1987 through 1992, a mean growth rate for HCFC-22 of 7.3
(±0.3)% yr-1 was estimated for this period.
HATS-93-008
- MONTZKA, S.A., M. TRAINER, P.D. GOLDAN, W.C.
KUSTER, and F.C. FEHSENFELD. Isoprene and its oxidation products, methyl vinyl ketone
and methacrolein, in the rural troposphere. Journal of Geophysical Research 98(D1),
1101-1111 (1993).
The mixing ratios of methyl vinyl ketone (CH2=CHCOCH3) and methacrolein (CH2=C(CH3)COH) were measured at a site located in the Kinterbish Wildlife
Management Area in western Alabama. The measurements were made between June 15 and July
20, 1990. Considering all the data over the whole measurement period, the concentrations
of these two cabonyls were approximately equal to this isolated rural site. The average
mixing ratios for methyl vinyl ketone and methacrolein were 0.98 ppbv and 0.66 ppbv,
respectively, while the medians were 0.87 ppbv and 0.57 ppbv. The methyl vinyl ketone
mixing ratio varied from 3.4 ppbv to the detection limit of the instrument, 0.01 ppbv,
while the methacrolein mixing ratio varied from 2.6 ppbv to 0.027 ppbv. These cabonyls
constituted a significant fraction of the volatile organic compounds observed at the site:
their mixing ratios measured 2 m above the top of the forest canopy were less than that of
the dominant compound, isoprene, but were considerably greater than the mixing ratios of
anthropogenic compounds (e.g., benzene). The mixing ratios of methyl vinyl ketone and
methacrolein were found to be highly correlated and exhibited a systematic variation with
respect to each other. On average, during the day, methyl vinyl ketone was larger than
methacrolein while methacrolein tended to be slightly larger during the night. The
systematic behavior of these compounds with respect to each other and other compounds
measured at the site were simulated using a one-dimensional photochemical model. These
observations were consistent with the production and loss of isoprene, methyl vinyl
ketone, and methacrolein by photochemical oxidation reactions.
HATS-93-009
- STURGES, W.T., and J.W. ELKINS. Use of
adsorbents to collect selected halocarbons and hydrohalocarbons of environmental interest
from large air volumes. Journal of Chromatography 642, 123-134 (1993).
Hydrohalocarbons are the proposed replacement compounds for the chlorofluorocarbons. They
will initially have very low concentrations, on the order of a ppt (v/v), in the global
atmosphere. Neither gas chromatography-electron-capture detection, nor gas
chromatography-mass spectrometry, have adequate sensitivity to measure such concentrations
directly from air samples; concentration techniques are required to achieve this. We have
examined a range of commercially-available adsorbents, including activated charcoals,
carbon molecular sieves, porous polymers, and graphitized carbons, for their suitability
as ambient temperature concentrating traps for a range of man-made halocarbons and
hydrohalocarbons (CFC-12, CFC-11, CFC-13, HCFC-22, HCFC-123 and HFC-134a). From our
measurements of specific retention and desorption volumes it was found that no one
adsorbent could both collect all of the target compounds with high efficiency, and also
allow efficient recovery by thermal desorption. A sequence of adsorbents is required. We
designed a 30 cm long 0.64 cm O.D. trap containing HayeSep DB (a porous polymer), Carboxen
1000 and Carbosieve S-11 (both carbon molecular sieves) to collect all of the target
compounds from a 5-l air sample at 25C and allow efficient recovery with 500 ml of
nitrogen carrier gas at 200C Good comparability was demonstrated between the adsorbent
trapping system and direct loop injection analysis for CFC-12 in ambient air. Precision
for all of the compounds analyzed with the adsorbent trap was better than 4%, and improved
to better than 1% when ratioed to CFC-12.
HATS-93-010
- STURGES, W.T., G.F. Cota, and P.T. BUCKLEY. Bromoform
emission from Arctic ice algae. Nature 358, 660-662 (1992).
Destruction of surface ozone in the Arctic environment during the spring is thought to be
caused by photochemical reactions involving bromine compounds. Berg et al. reported a
pulse of bromine particles and gases in the Arctic lower atmosphere in spring, which may
be responsible for this surface ozone destruction and for which biogenic sources have been
hypothesized. Here we report laboratory and in situ measurements which indicate that
Arctic ice microalgae emit significant quantities of bromoform (CHBr3),
which may be converted photochemically into active forms of bromine. Our estimates of
total annual bromoform release indicate that polar ice algae might contribute globally
significant amounts of organic bromine compounds, comparable with anthropogenic and
macrophyte sources.
HATS-93-011
- STURGES, W.T., R.C. SCHNELL, G.S. DUTTON, S.R.
Garcia, and J.A. Lind. Spring measurements of tropospheric bromine at Barrow, Alaska. Geophysical
Research Letters 20(2), 201-204 (1993).
The partitioning of bromine in the lower troposphere between particulate, inorganic
gaseous, and organic gaseous phases was measured during the arctic spring. Rapid
photochemical production of particulate Br from organic gaseous Br was indicated by 1) an
inverse correlation between particulate bromide and organic gaseous bromine (r2
= -0.67), 2) a diurnal cycle in the ratio of these two phases, and 3) a diurnal cycle in
the ratio of organic gaseous Br to Cl. Organic gaseous Br and Cl were correlated (r2
= 067) indicating a common, possibly marine, source.
HATS-93-012
- STURGES, W.T., C.W. Sullivan, R.C. SCHNELL,
L.E. Heidt, and W.H. Pollock. Bromoalkane production by Antarctic ice algae. Tellus
45B, 120-126 (1993).
Ice microalgae, collected from the underside of annual sea ice in McMurdo Sound,
Antarctica, were found to contain and release to seawater a number of brominated
hydrocarbons. These included bromoform, dibromomethane, mixed bromochloromethanes, and
methyl bromide. Atmospheric measurements in the McMurdo Sound vicinity revealed the
presence of bromoform and methyl bromide in the lower atmosphere, with lowest
concentrations inland, further indicating that biogenic activity in the Sound is a source
of organic bromine gases to the Antarctic atmosphere. This may have important implications
for boundary layer chemistry in Antarctica. in the Arctic, the presence of bromoform has
been linked to loss of surface ozone in the spring. We report here preliminary evidence
for similar surface ozone loss at McMurdo Station.
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