Global Retrievals of Aerosol Properties over Land from MODIS and SeaWiFS

Transcription

1 Global Retrievals of Aerosol Properties over Land from MODIS and SeaWiFS N. Christina Hsu M.-J. Jeong, S.-C. Tsay, M. D. King, and B. H. Holben Laboratory for Atmospheres NASA Goddard Space Flight Center Greenbelt, Maryland USA 1

2 2001 Perfect Dust Storm TOMS Aerosol Index - time series Aerosol Index # AI = 100 log R 340 R AI>0, Absorbing aerosols - AI<0, Non-Absorbing aerosols - Sensitive to aerosol height # Hsu et al., Geophys. Res. Lett., 23, , meas log R 340 R 380 Ray calc

3 Single View Aerosol Remote Sensing & Retrievals The early days of AVHRR, since 1983: Geogdzhayev, Mishchenko, et al., J. Atmos. Sci., = 0.55 m Optical Thickness July 1988 Monthly Mean Ångstrom Exponent July 1988 Monthly Mean The current days of MODIS, since 2000: Remer, Kaufman, Tanré, et al., J. Atmos. Sci., = 0.55 m Optical Thickness August 2003 Monthly Mean Fine-mode Fraction August 2003 Monthly Mean 3

4 MODIS Visible & NIR Bands: superimposed on the GOME spectral reflectance taken over the Sahara 412 nm 470 nm 645 nm 4

5 6 April 2001 MODIS Red-Green-Blue with Rayleigh scattering removed Current MODIS retrievals: Aerosol Optical Thickness New MODIS Deep Blue: Aerosol Optical Thickness

6 a Perfect Dust Storm 7 April 2001 SeaWiFS AOT Angstrom exponent 6

7 SeaWiFS RGB - Rayleigh Asian Dust Outbreak 6 April 2001 Deep Blue Algorithm: Cloud mask works very well Aerosol retrievals indicate dust storms originated from Gobi and Inner Mongolia regions Single scattering albedos are quite different between these two regions SeaWiFS AOT SSA (412nm)

8 Comparisons With AERONET During ACE-Asia (Mar-May 2001) 8

9 April 1 April 7 April 8 April 14 April 16 9 Daily MODIS AOT Images for Spring 2002 East Asia Dust plumes are associated with cold front passage Frequent cloud cover

10 Monthly Mean Aerosol Optical Thickness (550nm): Mid-East Deep Blue: June 2005 Deep Blue: July 2005 Deep Blue: August 2005 Dark-Target MODIS: June 2005 Dark-Target MODIS: July 2005 Dark-Target MODIS: August 2005 Composite: June 2005 Composite: July 2005 Composite: August

11 Monthly Mean Aerosol Optical Thickness (550nm): Africa Deep Blue: December 2005 Deep Blue: January 2005 Deep Blue: February 2005 Dark-Target MODIS: December 2005 Dark-Target MODIS: January 2005 Dark-Target MODIS: February 2005 Composite: December 2005 Composite: January 2005 Composite: February

12 Interactions of Saharan Dust and Tropical Cyclones (NAMMA) MODIS June Mean 550 nm AOT Differences (2006 minus 2005) 12

13 Seasonal Mean Aerosol Optical Depth (550nm): Composite of Deep Blue & Conventional MODIS AOTs MAM, Y2005 JJA, Y2005 SON, Y2005 DJF, Y

14 Time Series of April Monthly Mean of SeaWiFS Aerosol Optical Thickness : intensified dust activities at source regions : localized dust outbreaks, but extensive forest fires in : moderate dust activities, but increased air pollutions 14

15 Summary Deep-Blue Aerosol Retrievals: Provide long-term data records from SeaWiFS, MODIS, to future VIIRS in NPP/NPOESS; and Data available at: Specifically, Deep-Blue: provide aerosol properties near source regions to achieve a complete picture of aerosol information from source to sink for Climate Forcing; characterize the strengths and locations of dust source for Aerosol Transport Model; track iron sources from windblown dust for stimulating plankton growth in the open ocean for Carbon Cycle; and acquire timely atmospheric turbidity information over affected regions for Visibility and Adverse Health Effects. 15

16 Backup Slides 16

17 Flowchart for Deep Blue Algorithm Radiances 412, 490, 670 nm 3x3 Pixels Spatial 412/490 Absorbing Cloud Screening or Cloud Mask Algorithm Variance at 412 nm Aerosol Index NO RETRIEVAL 412 nm Surface Reflectivity (0.1ºx0.1º) Dust Model Yes Dust Dominant Cloudy? No Surface Reflectance Determination Aerosol Type Mixed Aerosols Maximum Likelihood Method 490, nm Surface Reflectivity (0.1ºx0.1º) Smoke Model Single-Scattering Albedo + Aerosol Optical Thickness 17 + Ångström Exponent

18 Surface Reflectance Data Base - Sep 2004 SeaWiFS 412 nm (nadir) SeaWiFS 670 nm (nadir) 18 MODIS/Aqua 412 nm (nadir) MODIS/Aqua 650 nm (nadir)