global distributions of carbonyl sulfide (ocs) in the upper troposphere and stratosphere michael...
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![Page 1: Global Distributions of Carbonyl Sulfide (OCS) in the Upper Troposphere and Stratosphere Michael Barkley & Paul Palmer, University of Edinburgh Chris Boone](https://reader035.vdocument.in/reader035/viewer/2022081516/56649d205503460f949f4b64/html5/thumbnails/1.jpg)
Global Distributions of Carbonyl Sulfide Global Distributions of Carbonyl Sulfide (OCS) in the Upper Troposphere and (OCS) in the Upper Troposphere and
StratosphereStratosphereMichael Barkley & Paul Palmer, University of EdinburghChris Boone & Peter Bernath† , University of Waterloo (†University of York)Parvadha Suntharalingham, UEA & Harvard University
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Michael Barkley, University of Edinburgh
Slide 2
Outline
Introduction♦ A quick tour of the OCS world - why is OCS important?
ACE retrievals of OCS ♦ What does the raw data tell us?
Validation - comparisons of ACE OCS to other OCS measurements♦ ACE vs. ATMOS v3 data (Shuttle-borne high resn. FTIR) ♦ ACE vs. MkIV data (Balloon-borne high resn. FTIR)
Global Distributions♦ Global Maps♦ Zonal means & latitudinal profiles♦ Estimate of OCS stratospheric Lifetime
Summary
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Michael Barkley, University of Edinburgh
Slide 3
Why is OCS interesting & important?
Most long-lived and abundant sulphur gas in the atmosphere
OCS oxidised in stratosphere to form sulfate aerosol - which supposedly ‘sustains’ the Stratospheric Sulfate Aerosol layer (SSA)♦ Attenuation of UV radiation♦ Surface for heterogeneous
chemistry More recently: uptake of OCS
by plants is very similar to uptake of CO2
♦ Can OCS constrain GPP/biospheric fluxes of C?
Uncertainty in budgetOCS seasonal cycle similar to CO2
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Michael Barkley, University of Edinburgh
Slide 4
OCS Global Budget
CS2
SO2 AerosolsStratosphere
Troposphere
41 (154)
-130 (56)
-238 (30)
64 (32)CS2DM
S
154 (37)
84 (54)
116 (58)
70 (50)
Kettle et al., JGR, 2002: Forward modelling approach: calculate global COS fluxes as sum of individual fluxes from sources & sinks
SO2 OCS
OCS
OCS(~2.5Tg)
OCS(~0.3Tg)
0.31Tg 0.34Tg
~9%
Chin & Davis, JGR, 1995Flux (error) [Gg S]
Atmospheric Losses:
OH: -94 (12)
O: -11 (5)
hv: -16 (5)
---------
Tot: -121 (14)
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Michael Barkley, University of Edinburgh
Slide 5
Source/sink seasonal variability
Seasonal cycle determined by:♦ NH: Vegetation and ocean♦ SH: Ocean
Sources & sinks drive variability in lower atmosphere
Kettle et al., JGR, 2002: Forward modelling approach: calculate global COS fluxes as sum of individual fluxes from sources & sinks
Suntharalingham et al, 2008
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Michael Barkley, University of Edinburgh
Slide 6
ACE OCS retrievals
Use improved v2.2 ‘research products’♦ More micro-windows &
higher altitudes Uses HITRAN 2004 8 interfering species fitted
simultaneously:
♦ OCS ♦ Isotopologue 2
♦ O3
♦ Isotopolgues 1 & 3
♦ CO2
♦ Isotopolgues 1,2,3 & 4
♦ H2O
Centre [cm-1]
Width [cm-1]
Low-z [km]
High-z [km]
2039.01 0.4 6 to 8 19 to 26
2040.50 0.5 8 to 10 20 to 26
2043.51 0.4 10 to 12 20 to 26
2044.01 1.4 17 22 to 31
2045.18 0.3 6 to 8 22 to 31
2048.03 0.4 6 to 8 23 to 31
2049.95 0.4 16 to 18 23 to 31
2051.30 0.4 6 to 8 23 to 31
2053.21 0.3 13 to 15 23 to 31
2054.45 0.5 12 to 15 23 to 31
2055.90 0.5 6 to 8 12 to 15
2057.52 0.45 6 to 8 12 to 15
Low z = 8 – 2 x [sin(lat)]2
Fitting windows
Pole to Equator
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Michael Barkley, University of Edinburgh
Slide 7
ACE OCS
Total # occultations = 10251
No data below ~6 km or above ~31 km
Few measurements > 600 pptv
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Michael Barkley, University of Edinburgh
Slide 8
ACE vs. MkIV Balloon ProfilesMkIV data courtesy of Geoff Toon, JPL, NASA
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Michael Barkley, University of Edinburgh
Slide 9
ACE measurements (not) near Fort Sumner
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Michael Barkley, University of Edinburgh
Slide 10
Comparing ACE to ATMOS: where & when?
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Michael Barkley, University of Edinburgh
Slide 11
ACE vs. ATMOSATMOS data courtesy of JPL, NASA
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Michael Barkley, University of Edinburgh
Slide 12
Some useful numbers…
Differences most likely due
to improvements
in spectroscopic parameters @ 5
microns
ACE – HITRAN 2004
ATMOS – Atmos line list
ATMOS ~ 10% > ACE
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Michael Barkley, University of Edinburgh
Slide 13
ACE OCS Global Distributions (2004-2006)
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Michael Barkley, University of Edinburgh
Slide 14
Zonal Seasonal Means
Profiles averaged in 15°latitude bins; only bins with a minimum of 10 profiles are plotted.
Distributions largely determined by atmospheric transport
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Michael Barkley, University of Edinburgh
Slide 15
Zonal Seasonal Means
Profiles averaged in 15°latitude bins; only bins with a minimum of 10 profiles are plotted.
HCN
HCN
HCN
CO
CO
CO
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Michael Barkley, University of Edinburgh
Slide 16
Zonal Seasonal Means
Profiles averaged in 15°latitude bins; only bins with a minimum of 10 profiles are plotted.
Data from: Atlantic cruises + Atlas-3
Notholt et al., Science, 2003
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Michael Barkley, University of Edinburgh
Slide 17
Seasonal Maps at 9.5 km
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Michael Barkley, University of Edinburgh
Slide 18
Seasonal Maps at 9.5 km
INTEX-A 1st July – 14th August 2004 (Blake et al. 2008)
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Michael Barkley, University of Edinburgh
Slide 19
Mean Latitudinal Profiles
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Michael Barkley, University of Edinburgh
Slide 20
Mean Latitudinal Profiles
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Michael Barkley, University of Edinburgh
Slide 21
OCS stratospheric lifetime
Long-lived trace gases in stratosphere are linearly correlated provided lifetime of one species is known, the lifetime of the other can be estimated [see Plumb & Ko, 1992]
T1 = T2 x (dΩ2/dΩ1) x (Ω1/Ω2)
Use coincidental ACE measurements of CFC-11 and CFC-12 + & CFC lifetimes & tropospheric VMRs from the WMO 2006 report: ♦ CFC-11 (CFCl3)
♦ Ω = 254 pptv, T=45±10 yrs♦ CFC-12 (CF2Cl2)
♦ Ω = 540 pptv, T=100±20 yrs Tropospheric OCS = 500 pptv
♦ Note, don’t use ACE value as it represents UT
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Michael Barkley, University of Edinburgh
Slide 22
Some more useful numbers…
Best estimate = 64±21 yrs
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Michael Barkley, University of Edinburgh
Slide 23
What does the stratospheric lifetime tell us?
‘Back of envelope’ calculation♦ OCS stratospheric sink =
total mass of OCS in atmosphere / stratospheric lifetime Using the best estimate for OCS lifetime = 64±21 yrs
♦ OCS stratospheric sink = 63 – 124 Gg OCS / yr♦ = 34 – 66 Gg S / yr
No OCS source in strats sink = tropospheric flux Tropospheric sulfur flux (in the form of OCS) required
to sustain the stratospheric sulfate aerosol layer (see Chin and Davis, JGR, 1995 & references therein)♦ = 30 – 170 Gg S / yr
i.e., our estimate is at the lower end of this range Answer: Need to re-examine OCS contribution to SSA
using ACE data and stratospheric sulfur/aerosol model
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Michael Barkley, University of Edinburgh
Slide 24
What does the stratospheric lifetime tell us?
‘Back of envelope’ calculation♦ OCS stratospheric sink =
total mass of OCS in atmosphere / stratospheric lifetime Using the best estimate for OCS lifetime = 64±21 yrs
♦ OCS stratospheric sink = 63 – 124 Gg OCS / yr♦ = 34 – 66 Gg S / yr
No OCS source in strats sink = tropospheric flux Tropospheric sulfur flux (in the form of OCS) required
to sustain the stratospheric sulfate aerosol layer (see Chin and Davis, JGR, 1995 & references therein)♦ = 30 – 170 Gg S / yr
i.e., our estimate is at the lower end of this range Answer: Need to re-examine OCS contribution to SSA
using ACE data and stratospheric sulfur/aerosol model
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Michael Barkley, University of Edinburgh
Slide 25
Summary
OCS important but large uncertainties in budget remain ACE has provided the first global OCS UT/stratosphere
distributions observed from space♦ Generally good agreement with other OCS measurements♦ Distributions governed by atmospheric transport ♦ Biomass burning is a significant source in SH tropics…
♦ …but is it weaker than previously thought?
Strong correlations with CFC-11 & CFC-12 yields: ♦ OCS stratospheric lifetime = 64 ± 21 yrs♦ OCS stratospheric sink = 63 – 124 Gg OCS / yr
Next step, (someone) must incorporate ACE OCS measurements into global CTM
Results submitted to GRL paper (in revision)
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EndEnd
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Michael Barkley, University of Edinburgh
Slide 27
ACE vs. Aircraft
GMD NOAA aircraft flights (grey lines) constrained to region: ♦ 40 - 48 °N♦ 89 - 104.3 °W
ACE sampled over:♦ 25 - 55 °N♦ 70- 125 °W♦ Necessary to get ACE
data down to ~8 km Construct mean aircraft
profile (red line) Interpolate across altitude
gap (if necessary) and smooth (light green line)
First complete trop-strat OCS profiles!
Aircraft data courtesy of Stephen Montzka GMD, NOAA
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Michael Barkley, University of Edinburgh
Slide 28
Summary of MkIV and ATMOS instruments
MkIV ♦ Balloon-borne high
resolution FTIR ♦ Covers 650-5650 cm-1
spectral region at 0.01 cm-1 resolution
♦ Solar Occultation ATMOS
♦ Atmospheric Trace Molecule Spectroscopy experiment
♦ Balloon-borne high resolution FTIR
♦ Covers 600-4800 cm-1 spectral region at 0.01 cm-1 resolution
♦ Solar Occultation
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Michael Barkley, University of Edinburgh
Slide 29
Finely balancing the OCS global budget
Total sources = 592 (166-1071)† [210-1049]*
Total sinks = 489 (380-597) † [902-1827]*
♦ † = Suntharalingham et al, JGR (sub), 2007 (GEOS-Chem)♦ * = Montzka et al, JGR, 2007 (Observations + Kettle fluxes)
“…within the large associated range of uncertainties..”
Kettle et al., JGR, 2002: Forward modelling approach: calculate global COS fluxes as sum of individual fluxes from sources & sinks
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Michael Barkley, University of Edinburgh
Slide 30
Past Variability
Sulfur emissions?
Deforestation?
Viscose rayon production of CS2?
Little Ice Age 1550-1850 AD
Drop not understood
Montzka et al., JGR, 2004