Presentation on theme: "Dylan Millet Harvard University with"— Presentation transcript:
1 Spatial Distribution of Isoprene Emissions from North America: New Constraints from OMI Dylan MilletHarvard UniversitywithD.J. Jacob and K.F. Boersma (Harvard), C.L. Heald (UC Berkeley),A. Guenther (NCAR), T.P. Kurosu and K. Chance (Harvard-Smithsonian)thanks toNASA-ACMAPNOAA C&GC Postdoctoral ProgramOMI Science TeamINTEX Science TeamsAmerican Geophysical Union Fall Meeting 2006 San Francisco, CA
2 VOCs Affect Atmospheric Chemistry and Climate IsopreneMost important non-methane VOCGlobal emissions ~ methane(but > 104 times more reactive)~ 6x anthropogenic VOC emissions
3 Mapping Isoprene Emissions from Space HCHO vertical columns measured by OMI(T.P. Kurosu & K. Chance)OH, hki, YiOH, hkHCHOVOCsHCHOVOC sourceDistancedownwindΩHCHOIsoprenea-pinenepropane100 kmdetectionlimitLocal ΩHCHO-Ei RelationshipPalmer et al., JGR (2003,2006).
4 Testing the Approach: ΩHCHO = SEisoprene+ B What drives variability in column HCHO?Error CharacterizationMeasured HCHO production rate vs. column amountMean biasPrecisionPHCHO (1012 molec cm-2 s-1)isoprene25–31% error (1σ) in HCHO satellite measurementsINTEX-A/BΩHCHO (1016 molec cm-2)clouds primary source of errorHCHO Column ComparisonΩHCHO variability over N. America driven by isoprene25x101525x1015Other VOCs give rise to a relatively stable background ΩHCHO Not to variability detectable from spaceURI (DC8)OMI25x101525x1015Millet et al., JGR (2006).NCAR (DC8)Aircraft
5 Defining Spatial Distribution of Eisoprene Using OMI HCHO HCHO columns from OMI satellite instrument (summer 2006)Isoprene emissions from the MEGAN biogenic emission inventory (summer 2006)?test bottom-up inventories against top-down constraints from OMImismatch in hotspot locationsimplications for OH, O3, SOA production
6 Model of Emissions of Gases and Aerosols from Nature Vegetation-specific baseline emission factorsEnvironmental drivers (T, h, LAI, leaf age, …)Guenther et al., ACP (2006)Drive MEGAN with 2 land cover databasesG2006Guenther  (MODIS3)CLMCommunity Land Model(AVHRR)MEGAN Isoprene Emissionsw/ G2006 vegetationMEGAN Isoprene Emissionsw/ CLM vegetation14.6 TgC12.2 TgC[1013 atomsC cm-2 s-1]
7 OMI vs. GEOS-Chem with MEGAN Emissions OMI HCHO: June-August 2006Similarity in broad spatial distribution (r2 = 0.86)GEOS-Chem HCHO: June-August 2006But important discrepancies regional & landscape scale emission hotspots[1015 molecules cm-2]
10 Spatial Patterns in Isoprene Emissions MEGAN higher than OMI over dominant emission regionsOMI – MEGAN Isoprene EmissionsJune-August, 2006MEGAN w/ G2006 Land CoverOzark PlateauUpper SouthWisconsin-MinnesotaLarge sensitivity to surface database usedMEGAN w/ CLM Land CoverCLM-driven MEGAN lower than OMI over deep South & Atlantic coast
11 Why are Emissions Overestimated in Dominant Source Regions? Bottom-up emissions are too high in Ozarks, upper South, MN/WIOMI – MEGAN Isoprene EmissionsJune-August, 2006MEGAN w/ G2006 Land CoverAverage Bias:Ozarks: 30-70%Upper South: 20-45%Large emissions driven by oak tree cover, high temperaturesBroadleaf tree isoprene emissions overestimated?MEGAN w/ CLM Land CoverG2006 Broadleaf Trees
12 Why Are CLM Emissions Too Low in Deep South? Average Bias: 50 to >100%OMI – MEGAN Isoprene EmissionsJune-August, 2006MEGAN w/ G2006 Land CoverUnderestimate of broadleaf tree or shrub coverage?CLM – G2006Broadleaf Tree CoverCLM – GuentherShrub CoverMEGAN w/ CLM Land CoverModeled emissions from evergreen trees or crops too low?CLMFineleaf EvergreensCLMCrops
13 ConclusionsOMI HCHO columns show similar magnitude & broad spatial patterns as state-of-the-art bottom-up emission inventories (R2 = 0.86) But reveal major discrepancies at the regional scaleBottom-up isoprene emission estimates are 20 to >70% too high in the dominant emission regions Ozarks, upper South, MN/WI Overestimate of broadleaf tree emissions?CLM-driven isoprene emission estimates are 50 to >100% too low over the deep South and along the Atlantic coast Underestimate of broadleaf tree and shrub cover? Underestimate of fineleaf evergreen or crop emissions?
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