tude, deg b822 8...12 rebecca hornbrook1,*, doug kinnison1, eric apel1, alan hills1, simone tilmes1,...
TRANSCRIPT
Rebecca Hornbrook1,*, Doug Kinnison1, Eric Apel1, Alan Hills1, Simone Tilmes1, Jean-Francois Lamarque1, Sue Schauffler1
Dan Riemer2, Elliot Atlas2, Valeria Donets2, Alfonso Saiz-Lopez3, and the TORERO and CONTRAST science teams
1Atmospheric Chemistry Division, NCAR, Boulder, CO, *[email protected]; 2Rosentiel School of Marine & Atmospheric Science, University of Miami, Miami, FL; 3Atmospheric Chemistry and Climate Group, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain.
B82
CONTRAST and TORERO Field Studies CONvective Transport of Active Species in the Tropics, Jan-Feb 2014, based in Guam, and the Tropical Ocean tRoposphere Exchange of Reactive Halogen species and Oxygenated VOC, Jan-Feb 2012, based in Chile and Costa Rica.
Chl-a
All CONTRAST Flights All TORERO Flights
Overview The bromine budget in the stratosphere is impacted significantly by the emissions and transport of very short lived halogenated species (VSLS) from the tropical marine boundary layer (MBL) to the stratosphere. Using VOC data from two recent field campaigns aboard the NSF/NCAR Gulfstream-V, we evaluate the CAM-Chem model using airborne observations of VSLS spanning from the MBL to the upper troposphere over both the eastern and western tropical Pacific Ocean.
CAM-Chem The Community Atmosphere Model with
chemistry, a component of the NCAR Community Earth System Model (CESM)
VOC tracers from several sources/types:
• Biogenic VOCs and oxidation products • Anthropogenic VOCs •Oil and Gas Tracers • Long-lived Halogenated VOCs • Short-lived Halogenated VOCs •OVOCs, including HCHO • DMS • Alkyl Nitrates • Biomass burning tracers (HCN, CH3CN)
TOGA The NCAR Trace Organic Gas Analyzer is a fast online gas chromatograph/mass spectrometer (GC/MS) capable of simultaneous measurements of 50+ VOCs.
CESM CAM-CHEM
• Global Chemistry-Climate Model
• ~1.0° horizontal resolution
• Specified Dynamics Version (GEOS5)
• 56 vertical levels (surface to ~ 2 hPa)
Lamarque et al., Geosci. Mod. Dev., 2012
Tropospheric Halogen Chemistry
Halogenated sources from the ocean
• Emissions following Chl-a over tropics
• Catalytic release from sea-salt
• Do NOT have polar emission processes
Chemical Processes
• Photochemistry (Cl, Br, and I)
• Dry/wet deposition
• 9 Additional vsl Organic species included.
• 160 species, 427 reactions
Installed on the NCAR/NSF G-V Ordoñez et al., ACP, 2012; Saiz-Lopez et al., ACP, 2012, Fernandez et al., ACP, 2014
Spatial Distributions: TOGA vs. CAM-Chem
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DMS, pptv
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CH2Br2, pptv
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CHBr3, pptv
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TOGA CAM-chem
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TOGA CAM-chem
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TOGA CAM-chem
CH2Br2
TOGA obs.
TOGA obs.
CAM-chem
CAM-chem
DMS. Comparisons of TOGA observations in the MBL and vertical distributions against CAM-Chem model output for CONTRAST (top) and TORERO (bottom). In general, the model predicts higher MRs in both regions. In the western region, the model predicts more variability than observed.
CHBr3. In the western region, MBL CHBr3 tends to be lower than the model, and not much higher than in the oligotrophic ocean.
CH2Br2. There is less variability in the western Pacific compared to the east, but overall the model is in very good agreement with the observations in both regions. Vertically, there is little difference between the regions, not surprising considering the 4 mo. lifetime of CH2Br2.
DMS
CO
NTR
AST
TO
RER
O
TOR
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C
ON
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TOGA obs.
TOGA obs.
CAM-chem
CAM-chem
CH2Br2 CHBr3
Aged Convection: CONTRAST RF05
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[VOC], pptv
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TOGA AWAS CC
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CONTRAST RF05, 1/22/14
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Br 3
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CH2Br2 (TOGA) CHBr3 (TOGA) DMS (TOGA) Acetone (TOGA)
CH2Br2 (CC) CHBr3 (CC) DMS (CC) GV Altitude
Guam
05:00 profile
06:30 profile
In this example, convection was sampled north of Guam, from a smaller-scale aged convective storm. Acetone (bottom plot) is slightly elevated between 04:00 and 05:00 UTC , indicating increased convection, but CHBr3 increases only slightly. Shorter-lived species are not observed aloft (i.e., DMS). The region is not impacted by wide-spread convection, thus no C-shapes in the altitude profiles.
CAM-Chem predicts more CHBr3 and DMS than was observed, both aloft and in the MBL, yet it captures the impact of the convection on both species. CH2Br2 is not predicted to change significantly.
Summary • Marine boundary layer mixing ratios of VSL species over the Western Pacific (CONTRAST study region) were
lower and less variable than over the Eastern Pacific Ocean (TORERO region). • Overall there is good agreement between the observations and CAM-chem. For many HCs and OVOCs (not
shown), the agreement is excellent. • CAM-chem tends to predict higher CHBr3 and DMS over both the Eastern and Western Tropical Pacific, although
the general spatial and vertical trends agree with the observations. • Moving forward, we are updating VSLS and DMS emissions inventories in CAM-Chem to see if we can achieve
better measurement-model agreement over the study regions. • Additionally, we will compare different model resolutions on the convective scale to see what, if any,
improvement we can achieve on the convective modeling.
Fresh Convection: CONTRAST RF12
Guam
Papua New Guinea
Palau
RF12
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CONTRAST RF12, 2/17/14
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CH2Br2 (TOGA) DMS (TOGA) CHBr3 (TOGA) GV Altitude
CH2Br2 (CC) DMS (CC) CHBr3 (CC)
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[VOC], pptv
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In this example, widespread convection was sampled near the ITCZ south of Guam. Note that the profiles are only from take-off and landing near Guam. DMS is observed aloft indicating recent convection. CAM-Chem predicts more CHBr3 and DMS than is observed aloft, and more DMS near the surface in Guam.
The C-shaped altitude profiles of CHBr3 and CH2Br2 indicate the difference between the regional background in the UT near the ITCZ and that near Guam that is less affected by widespread convection. The observations also suggest that the impact of the ITCZ is mostly cumulative, and not driven by localized convection.
Oligotrophic vs. Coastal: TORERO RF04, RF05
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29-Jan-2012; TORERO RF05; Time, UTC
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CH2ICl (TOGA) CH2Br2 (TOGA) CHBr3 (TOGA)
CH2ICl (CC) CH2Br2 (CC) CHBr3 (CC)
GV altitude
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27-Jan-2014; TORERO RF04; Time, UTC
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CH2ICl (TOGA) CH2Br2 (TOGA) CHBr3 (TOGA)
CH2ICl (CC) CH2Br2 (CC) CHBr3 (CC)
GV altitude
In this eastern Pacific near Chile, there is little convection, significant biological activity near the coast, and very little emissions of VSLS from the oligotrophic region (RF05). Here, CAM-Chem results for CHBr3, CH2Br2 and even CH2ICl are in very good agreement with the observations, despite the differences in lifetimes of the species.
RF05
RF04