The Asian Dust Events of April 1998 Prepared by: R. B. Husar, D. Tratt, B. A. Schichtel, S. R. Falke, F. Li D. Jaffe, S. Gassó, T. Gill, N. S. Laulainen, F. Lu. M Reheis, Y. Chun, D. Westpha, B. N. Holben, C. Geymard, I. McKendry, N. Kuring, G. C. Feldman, C. McClain, R. J. Frouin, J. Merrill, D. DuBois, F. Vignola, T. Murayama, S. Nickovic, W. E. Wilson, K. Sassen, N. Sugimoto Paper to be submitted to the JGR issue on dustJGR issue on dust December 27,

Asian Dust Cloud Source Region Fig 1 Daily aerosol pattern for East Asia and the Gobi region during April a)Daily aerosol pattern over the rectangular Gobi region consisting of 1) visibility-derived horizontal extinction coefficient averaged over nine stations, 2) AERONET sun photometer aerosol optical thickness data for Dalanzagdad and 3) regional average TOMS signal. The data show an aerosol peak on April 15 and a much larger peak starting April 19. b)Daily time series of the TOMS aerosol index for April 1998 averaged over East Asia.

April 15 Dust Cloud Over Asia Figure 2. Surface reflectance derived from the SeaWiFS satellite data for April and April The spectral reflectance data were rendered as a "true color" digital image by combining the blue (442 nm), green (550 nm), and red (670 nm) channels. The TOMS absorbing aerosol index (level 2.0) is superimposed as green contours. The April 19 image contains SeaWiFS, TOMS (green contour), surface wind speed > 15 m/s (red contour) and surface dust report from visibility data (blue circles). The line graph on the April 19 image is the change of the spectral reflectance of soil with increasing dust. Also, the graph shows yellow coloration of white clouds viewed through a dust layer.

April 19 Dust Cloud Over Asia Figure 2. Surface reflectance derived from the SeaWiFS satellite data for April and April The spectral reflectance data were rendered as a "true color" digital image by combining the blue (442 nm), green (550 nm), and red (670 nm) channels. The TOMS absorbing aerosol index (level 2.0) is superimposed as green contours. The April 19 image contains SeaWiFS, TOMS (green contour), surface wind speed > 15 m/s (red contour) and surface dust report from visibility data (blue circles). The line graph on the April 19 image is the change of the spectral reflectance of soil with increasing dust. Also, the graph shows yellow coloration of white clouds viewed through a dust layer.

Figure 3. Dust transport over the Pacific Ocean between April In the SeaWiFS images [Kuring, 1998], the dust appears as a yellow dye marking its own position at noon each day.

Dust Cloud Over North America Figure 4. GOES 10 geostationary satellite image of the dust taken on the evening of April 27. The dust cloud, marked by the brighter reflectance covers the entire northwestern US and the adjacent portions of Canada. A dust stream is also seen crossing the Rocky Mountains to the east.

West Coast PM10 Concentration Figure 5 PM10 concentration over the west coast based on 150 AIRS monitoring network stations. a) Daily concentration averaged over 150 sites every sixth day and 20 sites every day. During the in-between days, the number of active monitoring sites varied. b) Contour map of the PM10 concentration on April 29, 1998.

West Coast PM10 Concentration Figure 6. Diurnal pattern of dust of Northern California. a) Hourly PM10 concentration averaged over 12 stations in Northern California. b) Diurnal pattern of PM10 on April 29, c) Location of the hourly PM monitoring sites in northern California.

IMPROVE Fine Particle Dust Concentrations Figure 7. Fine Particle dust concentration pattern based on the IMPROVE speciated aerosol sampling network data. April 25, 1998 April 29, 1998 May 2, 1998

Fine Particle Dust Ten Year Trends Figure 8. Ten-year trend of fine particle dust concentration at three IMPROVE monitoring sites.

Vertical Profile of Dust Cloud Over North America Figure 9. Lidar profiles of the Asian dust cloud over North America. Lidar backscatter at JPL, Pasadena.Lidar profiles at Salt Lake City

Asian Dust Size Distribution Over North America Figure 10. Size distribution of the Asian dust measured in Korea [Chun et al., 2000], on the UW aircraft (Gassó 1999), and in the PNL aircraft [Laulainen et al., 2000].

Excess Spectral Reflectance of Dust Over the Ocean Figure 11. a. Excess spectral reflectance of dust over the ocean. b. Change of the spectral reflectance of soil with increasing dust. Also, the figure shows yellow coloration of white clouds viewed through a dust layer.

Solar Radiation Data for Eugene, OR Figure 12. Solar radiation data for Eugene, OR for April 20 and April 27, 1998 [Vignola, 1999].