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William K. M. Lau NASA/GSFC Laboratory for Atmospheres Co-author: K. M. Kim/GEST

Effects of Saharan dusts on weather and climate over the Atlantic: How Nature foiled the 2006 hurricane forecasts. William K. M. Lau NASA/GSFC Laboratory for Atmospheres Co-author: K. M. Kim/GEST. Effects of Saharan dusts on weather and climate over the Atlantic.

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William K. M. Lau NASA/GSFC Laboratory for Atmospheres Co-author: K. M. Kim/GEST

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  1. Effects of Saharan dusts on weather and climate over the Atlantic: How Nature foiled the 2006 hurricane forecasts William K. M. Lau NASA/GSFC Laboratory for Atmospheres Co-author: K. M. Kim/GEST

  2. Effects of Saharan dusts on weather and climate over the Atlantic • Annual emission of Saharan dust is estimated to be 4 billion tons • Increased Saharan dust outbreak since the 1970’s, associated with the prolonged drought in Sahel and increased dust storm over the Sahara desert Possible weather and climate impacts: • SAL dry air may suppress tropical cyclogenesis, and/or hurricane formation • Microphysics effects: suppress warm rain; increase ice-nucleation and deep convection • Solar Dimming Effect • “ Elevated Heat Pump” Effect MODIS Images

  3. How did nature foil the 2006 hurricane forecasts?

  4. El Nino-SST effect Dust-SST “Solar Dimming” effect Dust appears to be the primary cause for SST cooling in the MDR; El Nino is associated with reduced SST (and increased vertical shear) in the eastern equatorial Atlantic, suppresses cyclogensis

  5. More dust means lesser number of days of tropical cyclones

  6. Correlations of HC/TS statistics with a) Barbados dust and b) El Nino SST, 1980-2007 TS = sustained wind speed > 34 knts (17 m/s) HC = sustained wind speed >64 knts (33 m/s)

  7. The “Elevated Heat Pump” effect : fvGCM simulation of radiative Effect on circulation and climate of the West African region Caribbean Africa

  8. Gulf of Guinea Africa

  9. Estimate of anomalous (aerosol+ water cycle feedback) surface energy flux over the N. Atlantic/Caribbean region Short wave flux = -30.4 Wm-2 Longwave flux = 5.9 Wm-2 Sensible heat flux = 2.1 Wm-2 Latent heat flux = 8.6 Wm-2 Net surface flux = -14.1 Wm-2

  10. Anomalous Overturning Circulation induced by “Elevated Heat Pump” effect for WAM increased upper level clouds reduced upper level clouds induced subsidence suppresses convection increased low level clouds reduced SW cools land dust source increased moisture influx Africa reduced SW cools ocean Caribbean Region

  11. West Africa East Atlantic Caribbean

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