Figure 5.3: (a) Aerosol
optical depth and (b) Ångström exponent from POLDER satellite data
for May 1997 (Deuzé et al., 1999). The largest optical depths over the
Atlantic Ocean are from north African dust. The Ångström exponent expresses
the wavelength dependence of scattered light between 670 and 865 nm. The African
dust plume has a small Ångström exponent due to the importance of coarse
mode aerosols whereas the larger Ångström exponents around the continents
show the importance of accumulation mode aerosols in those locations.