seasonal variability of utls hydrocarbons observed from ace and comparisons with waccm
DESCRIPTION
Seasonal variability of UTLS hydrocarbons observed from ACE and comparisons with WACCM. Mijeong Park , William J. Randel, Louisa K. Emmons, and Douglas E. Kinnison National Center for Atmospheric Research. UTLS Workshop, Boulder, Oct. 19-22, 2009. Hydrocarbons – UTLS? . sources. sinks. - PowerPoint PPT PresentationTRANSCRIPT
Seasonal variability of UTLS hydrocarbons observed from ACE and comparisons with WACCM
Mijeong Park, William J. Randel, Louisa K. Emmons, and Douglas E. Kinnison
National Center for Atmospheric Research
UTLS Workshop, Boulder, Oct. 19-22, 2009
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• Useful as tracers in the UTLS• Global satellite measurements (ACE-
FTS)• Chemistry transport model (WACCM3)
Hydrocarbons – UTLS?
CO
C2H6HCN
sources
Biomass Burning
lifetime2 months
1.5 months
~4 years (free atmosphere)3 months (ocean contact)
sinksOH
OHOH, O(1D)ocean
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ACE-FTS• Atmospheric
Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is a high spectral resolution infrared Fourier Transform Spectrometer on SCISAT-1
• ACE-FTS measures atmospheric absorption spectra (750-4400cm-1) using solar occultation technique
• CO, HCN, C2H6, C2H2, OCS, CH3Cl, O3, HNO3, HCl,…
Tropical sampling ~ 4 times/year
FEB APR AUG OCT
ACE-FTS Observations
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Model Description1) Whole Atmosphere Community
Climate Model, version 3 (WACCM3)2) Driven with GEOS5.1 analyzed
meteorological fields3) Period: 2004 – 2007 (4 years)4) Resolution: 1.9°x2.5° (lat x lon); 88
levels (surface - 150 km)5) Includes detailed tropospheric
chemistry mechanism (125 species)6) Emissions specific to each year
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Carbon Monoxide (CO)ACE CO
ACE CO
WACCM3 CO
WACCM3 CO
DJF
JJA
Zonal mean climatology (4 years of data)
Good agreement
between ACE and WACCM3
min
max
max
min
tropopause
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Ethane (C2H6)WACCM3 C2H6
WACCM3 C2H6
ACE C2H6
ACE C2H6
DJF
JJA
Overall agreement, but WACCM3 is higher in the lower stratosphere(convection?)
Zonal mean climatology
CO – Horizontal Map
WACCM3 CO 147 hPa WACCM3 CO 147 hPa
ACE CO 13.5 km ACE CO 13.5 kmDJF JJA
max (Africa, America, Maritime continent)
max (Asian Monsoon)
max
max
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C2H6 – Horizontal Map
ACE C2H6 13.5 km ACE C2H6 13.5 km
WACCM3 C2H6 147 hPa WACCM3 C2H6 147 hPa
DJF JJA
Reasonable agreement except higher noise in ACE
max
max
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HCN – Horizontal Map
WACCM3 HCN 147 hPa WACCM3 HCN 147 hPa
ACE HCN 13.5 km ACE HCN 13.5 kmDJF JJA
max (Africa – DJF, Asian Monsoon – JJA)min (ocean)
max min
tropical minimum:air with recentocean contact
Asian monsoon anticyclone as
a pathway to the stratosphere
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monsoonmaximum
minimum for air with recent ocean contact
tropical min
transport tostratosphere via monsoon
ACE HCN Climatology
(JJA, 16.5 km)
ACE HCN (JJA)
Hydrogen Cyanide (HCN)
WACCM3 HCN (JJA)
(Summer, JJA)
Similar structure, but higher values in
WACCM3
ACE HCN (JJA)
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MLS HCN - Time vs. Lat
WACCM3 HCN (16-24 km) 2004-2007
MLS HCN (100 hPa) + ACE HCN (16-24 km)
Maxima in NH summer subtropics, linked to Asian summer monsoon
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Time Series (15°S-15°N)CO 17.5 km
C2H6 19.5 km
HCN 17.5 km
annual cycle – right above the tropopauseWACCM3 has very good agreement with ACEannual cycle
interannual variability(2 year cycle?)
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Annual Cycle - UTLSMLS CO
mean d(lnCO)/dz
CO Annual Cycle AmpRandel et al. (2007)
CO annual cycle - driven by the seasonal variation in upwelling acting on the strong background vertical gradient in CO
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CO & HCN – annual cycle? dCO/dz
strong vertical gradient
CO Annual Cycle
strong annual cycle
HCN Annual Cycle
dHCN/dz
CO
HCN
WACCM3climatolo
gyvertical gradient
normalized annual cycle amplitude
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Tracer-tracer CorrelationsDJF JJA
HCN
C2H6
high altitude (15.5-21.5
km)low altitude
(8.5-14.5 km)
high correlation
(annual cycle)
no correlation
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Summary1.Seasonal variability of hydrocarbons in the
tropical UTLS is analyzed using the ACE-FTS observations and WACCM3.
2.WACCM3 simulates seasonal cycles in the UTLS reasonably well.
3.Strong annual cycle is observed for the chemical tracers with strong vertical gradient (CO and C2H6) right above the tropical tropopause.
4.HCN is a unique tracer with minimum in tropical upper troposphere. Transport to stratosphere through Asian summer monsoon circulation.
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HCN ChemistryProduction Processes (i.e., Emissions)…
•HCN emissions were estimated by scaling CO emissions from biomass burning and biofuel combustion using HCN/CO = 0.012 mol/mol.•Biofuel combustion emissions are constant year-round (primarily domestic heating and cooking).•Biomass burning emissions are monthly averages over 1997-2006 from the GFED-v2 inventory [Van der Werf et al., ACP, 2006].Loss Processes…
• HCN + OH => products. [Strekowski et al, 2001]• HCN + O(1D) => products [Strekowski et al, 2001]• Wet deposition in the troposphere.• Dry deposition over ocean surface.
Seasonal cycleof HCN
from ACE-FTS
HCN source: biomass burning
HCN lifetime: ~4 years in free atmosphere, but sink from contact with ocean