Single Racetrack, Observed (approx) isoprene, pptv 1000 (North) 2000 (South) isoprene+ MVK+MAC, pptv 2000 (North) 4000 (South) MOZART-4/MEGAN isoprene +products, pptv 6000 (North) 9000 (South)

Influence of urban St. Louis, MO region is strongest at the northernmost point of the racetrack, with a gradual transition to the south, opposite the biogenic VOCs.

Rebecca Hornbrook1,*, Eric Apel1, Alan Hills1, Dan Riemer2, Nicola Blake3 and the NOMADSS Science Team

1Atmospheric Chemistry Division, NCAR, Boulder, CO, *rsh@ucar.edu; 2Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL; 3Dept. of Chemistry, University of California Irvine, Irvine, CA.

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O, 3

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thylfu

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Altitude a-pinene isoprene MBO MVK 3-methylfuran

•Deployed on the NSF/NCAR C-130 during NOMADSS •Provided 35-second integrated samples every 2 minutes •samples processed in flight using fast online GC/MS •chromatograms analyzed post-flight for approx. 85 VOCs •wide dynamic range, with low pptv to sub-pptv range DLs

TOGA (Trace Organic Gas Analyzer)

SAS/NOMADSS/SOAS, 06/13-07/13

SAS: The Southeast Atmosphere Study, which included: NOMADSS: Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks, which included: SOAS: Southern Oxidant & Aerosol Study SOAS objectives included the direct quantification of VOC, ozone and NOx surface fluxes to reconcile differences with "blank-down" emission estimates, and to gain a better understanding of HOx/NOx/ozone/organics/ aerosol distributions, sources and sinks.

TOGA-observed Biogenic Hydrocarbons: isoprene MVK (methyl vinyl ketone) methacrolein 3-methylfuran MBO (2-methyl-3-buten-2-ol)

alpha-pinene camphene alpha-terpinene para-cymene beta-pinene/myrcene limonene/d-3-carene

monoterpenes

Selected NOMADSS Flights

RF03: Missouri, Arkansas

a

b c

d Observed (approx) isoprene, pptv (a) 700 (b) 1000 (c) 1000 (d) 700

isoprene+ MVK+MAC, pptv (a) 1300 (b) 2000 (c) 2000 (d) 1600

a+b-pinene, pptv (a) 12 (b)12 (c) 12 (d)50-100

MOZART-4/ MEGAN-v2.1 isoprene +products, pptv (a) 6000 (c) 9000 (b) 5000 (d) 7000

terpenes +products, pptv (a) 300 (c) 400 (b) 200 (d) 600

Highest [terpenes] were observed in racetrack (d), consistent with both model and emissions. MBO is highly correlated with terpenes.

Emissions 18Z, 900 hPa

RF04: Alabama, Mississippi

a b c d

RF03

RF18

RF04

RF17

a b

c

d a

b c

d

Observed (approx) isoprene, pptv (a) 2600 (b) 1700 (c) 1200 (d) 2700

isoprene+ MVK+MAC, pptv (a) 5000 (c) 3500 (b) 4500 (d) 6000

a+b-pinene, pptv (a) 200 (c) 180 (b) 150 (d) 100

MOZART-4/ MEGAN-v2.1 isoprene +products, pptv (a) 9000 (c) 8000 (b) 9000 (d) 9000

terpenes +products, pptv (a) 1000 (c) 800 (b) 1000 (d) 900

Chemical forecast mixing ratios tend to be at least 2x observations.

Emissions 18Z, 900 hPa

RF17: Southeast Missouri

Emissions 18Z, 900 hPa

RF18: Tennessee, evening flight

Single Racetrack, Observed (approx) isoprene 2100 Z – 1200 pptv 0100 Z – 600 pptv 0300 Z – 50 pptv

isoprene+MVK+MAC 2100 Z – 3000 pptv 0100 Z – 1500 pptv 0300 Z – 450 pptv

a+b-pinene 2100 Z – 30 pptv 0100 Z – 10 pptv 0300 Z – bdl

MOZART-4/MEGAN-v2.1 isoprene+products 2100 Z – 9000 pptv 0100 Z – 9000 pptv 0300 Z – 9000 pptv

terpenes+products 2100 Z – 200 pptv 0100 Z – 200 pptv 0300 Z – 200 pptv

Observed [isoprene+MVK+ MAC], [terpenes] decrease in the evening, as does the emissions inventory, while the chemical forecast mixing ratios stay nearly constant, indicative of lifetimes being too long in the model.

Emissions 900 hPa

Summary

• Isoprene, MVK, methacrolein and 3-methylfuran were highly correlated in the BL in the southeast US. Higher OVOC/isop were seen in some BL air, the free troposphere, and into the evening.

• Observed distributions of BVOCs in the BL tend to agree with the emissions inventory, yet observed MRs are generally lower than chemical forecasts, probably due to isoprene and terpene tracer lifetimes being too long in the model. Full-chemistry model runs are planned for a more thorough comparison.

• Terpenes and MBO are well-correlated in the southeast, although mixing ratios of isoprene, MVK and methacrolein dominate the BVOC loading, unlike in CO forests, where [MBO] > [isoprene].

MOZART-4 model forecasts courtesy of Louisa Emmons, ACD/NCAR.

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NOMADSS RF18, 7/12/13; UTC

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Altitude isoprene MVK/isoprene a-pinene/isoprene MBO/isoprene 3-methylfuran/isoprene

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Altitude a-pinene isoprene MBO MVK 3-methylfuran

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NOMADSS RF04, 6/12/13; UTC

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Altitude a-pinene isoprene MBO MVK 3-methylfuran

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NOMADSS RF03, 6/8/13; UTC

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Altitude 3-methylfuran/isoprene MVK/isoprene a-pinene/isoprene MBO/isoprene isoprene

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37.4

37.2

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NOMADSS RF17, 7/11/13; UTC

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altitude latitude isoprene benzene