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Using the GEOS-Chem CTM to help evaluate the GlobAerosol daily merged/AATSR AOD product

Using the GEOS-Chem CTM to help evaluate the GlobAerosol daily merged/AATSR AOD product. Paul Palmer and Win Trivitayanurak http://www.geos.ed.ac.uk/eochem.

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Using the GEOS-Chem CTM to help evaluate the GlobAerosol daily merged/AATSR AOD product

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  1. Using the GEOS-Chem CTM to help evaluate the GlobAerosol daily merged/AATSR AOD product Paul Palmer and Win Trivitayanurak http://www.geos.ed.ac.uk/eochem

  2. Talk Outline1) Data used; Model description2) Model and observed monthly mean statistics3) Validation: Aeronet and AATS144) AOD and speciation of continental outflow regions5) Concluding remarks

  3. For this study we use:1) daily merge files2) daily AATSR files 3) orbit AATSR files (analysis not shown)We use only data that:1) cloud fraction < 0.8 (< 0.5 over land)2) do not include sunglint3) fitting uncertainty < 10% of retrieved AOD

  4. GEOS-Chem chemistry transport modela) 4x5o resolutionb) uses assimilated meteorology from the NASA GMAO NWP modelc) dust, anthropogenic, carbonaceous sources…d) primary and secondary organicse) sampled at 9-12 LT coinciding with satellite overpassf) sampled at individual measurement locationsData comparisonsa) generally, the model is sampled at the nearest 4x5o gridpoint to observationsb) we only consider Globaerosol measurements within 100 km from an AERONET sitec) we compare Globaerosol measurements that fall in the same 0.5x0.5ogridbox as aircraft datad) we compare median values unless otherwise stated

  5. Globaerosol Merged Daily product GEOS-Chem January 2004 July 2004

  6. GEOS-Chem AODs are generally smaller than Globaerosol daily merged AODs January 2004 July 2004

  7. Globaerosol AATSR Daily product GEOS-Chem January 2004 July 2004

  8. GEOS-Chem AODs agree slightly better with revised AATSR data (smaller bias and higher r) January 2004 July 2004

  9. GEOS-Chem AOD budget, January 2004 Model sampled for merged daily product

  10. GEOS-Chem AOD budget, July 2004 Model sampled for merged daily product

  11. AERONET (AErosol RObotic NETwork) is a network of ground-based sun photometers AERONET stations for 550 nm monthly statistics (using daily means) chosen based on AeroCom assessment

  12. GEOS-Chem (--) Aeronet (o) Abracos Hill (S. America): Aug-Nov BB Globaerosol (o): SO4, BC, OC, SS, DD GEOS-Chem: SO4, BC, OC, SS_A, SS_C, DD AOD Anmyon (E. Asia): Spring dust DOY

  13. GEOS-Chem (--) Aeronet (o) Cape Verde: Dust off N. Africa Globaerosol (o): SO4, BC, OC, SS, DD GEOS-Chem: SO4, BC, OC, SS_A, SS_C, DD AOD GSFC: Suburban E. US DOY

  14. AOD comparison between: (1) Globaerosol, (2) GEOS-Chem and (3) NASA Ames Airborne Tracking Sun photometer (AATS) during Summer 2004 • AATS: upward-looking instrument captures typically > 95% of the total column AOD (based on limited comparison with coincident shipborne measurements) • Provides AOD at 13 wavelengths, 354—2138 nm • Original work (Russell, et al, JGR, 2007) compared values with MODIS and MISR • Globaerosol comparison possible with only 5 (out of 15 flights)

  15. Daily GEOS-Chem fields sampled for all AATS14 measurement locations AATS14 AOD GEOS-Chem AOD

  16. Globaerosol comparison with AATS14 Globaerosol: SO4, BC, OC, SS, DD AATS14 AOD GEOS-Chem (black)/Globaerosol (color = aerosol type) AOD

  17. Model and observed AOD variations in major continental outflow regions (merged product) DOY

  18. Model and observed AOD variations in major continental outflow regions (merged product) DOY

  19. Using the revised AATSR product does not improve model agreement but highlights problems with speciation AATSR DOY Merged DOY

  20. Orbit AATSR data: Alternative AOD retrievals based on other aerosol types do not improve agreement with the model.

  21. Concluding remarks Globaerosol AOD retrievals (even after improved cloud screening): 1) are generally higher than the model and in situ data2) have little skill in reproducing continental in situ data (AERONET) in contrast to the coarse-scale CTM3) qualitatively agree better with the model AODs over the ocean downwind of continental outflow4)should be better informed regarding aerosol type (although alternative retrievals do not dramatically improve agreement with the CTM)

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