Aerosol Characterization Using the SeaWiFS Sensor and Surface Data E. M. Robinson and R. B. Husar Washington University, St. Louis, MO 63130 Technical Challenge: Aerosol Characterization PM characterization needs many different instruments and analysis tools Each sensor/network covers only a fraction of the 6-Dim PM data space (X, Y, Z, T, Diameter, Composition) Most of the 6D pattern is extrapolated from sparse measured data Satellite-Integral Satellites, integrate over height H, size D, composition C, shape, and mixture dimensions; these data need de-convolution of the integral measures. Co-Retrieval of Surface and Aerosol Properties Apparent Surface Reflectance, R Aer. Transmittance Both R 0 and R a are attenuated by aerosol extinction T a which act as a filter Aerosol Reflectance Aerosol scattering acts as reflectance, R a adding airlight to the surface reflectance Surface Reflectance The surface reflectance R 0 is an inherent characteristic of the surface R = (R 0 + (e - 1) P) e - The surface reflectance R 0 objects viewed from space is modified by aerosol scattering and absorption. The apparent reflectance, R, is: R = (R 0 + R a ) T a Aerosol as Reflector: R a = (e - 1) P Aerosol as Filter: T a = e - Apparent Reflectance R may be smaller or larger then R 0, depending on aerosol reflectance and filtering. Aerosols Increase of Decrease the Surface Reflectance, f(P/R 0 ) Aerosols will increase the apparent surface reflectance, R, if P/R 0 < 1. For this reason, the reflectance of ocean and dark vegetation increases with . When P/R 0 > 1, aerosols will decrease the surface reflectance. Accordingly, the brightness of clouds is reduced by overlying aerosols. At P~ R 0 the reflectance is unchanged by haze aerosols (e.g. soil and vegetation at 0.8 um).. At large (radiation equilibrium), both dark and bright surfaces asymptotically approach the aerosol reflectance, P The critical parameter influencing the apparent reflectance, R, is the ratio of aerosol phase function (angular reflectance), P, to bi-directional surface reflectance, R 0, (P/ R 0) Haze Effect on Spectral Reflectance over Land The spectral reflectance of vegetation in the visible is low at 0.01