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Variability of CH 2 O during ICARTT: Implications for GOME/OMI

Variability of CH 2 O during ICARTT: Implications for GOME/OMI. Dylan Millet. GEOS-CHEM Users’ Meeting April 2005. Use ICARTT flight data to address: Satellite retrievals Is GEOS-CHEM accurately representing the CH 2 O vertical profile (shape factor)?

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Variability of CH 2 O during ICARTT: Implications for GOME/OMI

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  1. Variability of CH2O during ICARTT:Implications for GOME/OMI Dylan Millet GEOS-CHEM Users’ Meeting April 2005 GEOS-CHEM Meeting 2005

  2. Use ICARTT flight data to address: • Satellite retrievals • Is GEOS-CHEM accurately representing the CH2O vertical profile (shape factor)? • What is the uncertainty/bias in the AMF? • Variability in CH2O • What are the dominant sources of CH2O over N.A.? • Implications for satellite retrievals? GEOS-CHEM Meeting 2005

  3. Air Mass Factor AMFG: Geometric factor w(s): Scattering weights ~ -(lnIB)/ t S(s): Shape factor Normalized vertical distribution From model AMF: Slant column / vertical column dt

  4. Vertical Profile Comparison All profiles E. U.S. Atlantic GEOS-CHEM Meeting 2005

  5. Clear Sky AMF Comparison- all profiles - Small negative bias (-6%) in modeled clear sky AMF GEOS-CHEM Meeting 2005

  6. Continental profiles: -7% Oceanic profiles: +5% GEOS-CHEM Meeting 2005

  7. Cloudy AMF Comparison Clouds: Can act to increase or decrease sensitivity of measurement GEOS-CHEM Meeting 2005

  8. Cloudy AMF Comparison Actual cloud profile: Retrieved cloud: GEOS-CHEM Meeting 2005

  9. Cloudy AMF Comparison Accounting for clouds: Small negative bias persists, larger spread GEOS-CHEM Meeting 2005

  10. Continental profiles: -17% Oceanic profiles: +3% GEOS-CHEM Meeting 2005

  11. CH2O Sources & Variability GEOS-CHEM Meeting 2005

  12. CH2O Sources Importance of measured precursors to CH2O production: GEOS-CHEM Meeting 2005

  13. CH2O Sources GEOS-CHEM Meeting 2005

  14. CH2O Sources Continental boundary layer: • Continental BL: • P(isoprene) ~ 50% of P(total) on average • OVOCs, methane important • Variability in P(isoprene) > 10x P(others) GEOS-CHEM Meeting 2005

  15. Conclusions • Error in AMF: • Uncertainty of ±30% (2s) for an individual clear-sky scene (higher for cloudy-sky) • Mean bias ~ -7% continental clear-sky; -17% continental cloudy-sky • Sources of CH2O: • Isoprene, OVOC, methane dominant sources over N.A. • Variability in isoprene source > 10x that of other sources GEOS-CHEM Meeting 2005

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