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North African Dust Export

(Ridley et al., in prep.). North African Dust Export. David A. Ridley, Colette L. Heald. A global 3-D model analysis using MODIS, MISR, CALIPSO, and AERONET observations.

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North African Dust Export

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  1. (Ridley et al., in prep.) North African Dust Export David A. Ridley, Colette L. Heald A global 3-D model analysis using MODIS, MISR, CALIPSO, and AERONET observations We gratefully acknowledge the MODIS team for the data supplied via the NASA Goddard website, and especially Jingfeng Huang for his help, the CALIPSO team for the retrievals used, all the PIs for the AERONET sites we used from across the world, and Joe Prospero for his dust concentration data.

  2. Mass Partitioning of Sub-Micron Dust • Equal vs realistic partitioning • GEOS-Chem Annual AOD (2006) • Dust size distribution from the SHADE campaign (Highwood et al., 2003) • AOD decreased by 10-20% • Due to size dependence of scattering • NB no change in total dust mass • AOD contribution from dust size bins Original uniform mass partitioning New dust mass partitioning

  3. Spatial Distribution of AOD

  4. Spatial Distribution of AOD

  5. Vertical Structure of Plumes • Aerosol extinction across the Atlantic averaged over 15 deg latitudal bands (2007) Marine aerosol? (cfKaterynaLapina) • Seasonality in vertical distribution reproduced well • Missing aerosol close to ocean surface – dust and marine?

  6. Deposition of African Dust • Deposition of phosphorus (dust) in the Atlantic, Caribbean, and Amazon • Annual westward export 235±45Tg (240±80Tg from MODIS1) • Deposition to Atlantic is slightly higher than other studies1,2,3,4 • Deposition to the Amazon is lower than observed1,5 Tg 1 Kaufman et al., 2005 2 Ginoux et al., 2004 3 Prospero et al., 1996 4 Fan et al., 2004 5 Mahowald et al., 2005

  7. Deposition of African Dust • Deposition of phosphorus (dust) in the Atlantic, Caribbean, and Amazon • Annual westward export 235±45Tg (240±80Tg from MODIS1) • Deposition to Atlantic is slightly higher than other studies1,2,3,4 • Deposition to the Amazon is lower than observed1,5 1 Kaufman et al., 2005 2 Ginoux et al., 2004 3 Prospero et al., 1996 4 Fan et al., 2004 5 Mahowald et al., 2005

  8. Conclusions Positives • Seasonality and source regions of dust well reproduced • Vertical distribution agrees well with CALIPSO observations • Dust concentrations in Caribbean correlate well with observations (R=0.7-0.9) • GEOS-Chem shows greater inter-annual variability than obs • Emissions from Bodele Depression are under represented • Dust deposition to Amazon lower than expected Not-so Positives

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