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Wavelength dependence of the single scattering albedo Single scattering albedo (SSA) values at 450(blue), 550(green) and 700(red) nm The SSA values during.

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Presentation on theme: "Wavelength dependence of the single scattering albedo Single scattering albedo (SSA) values at 450(blue), 550(green) and 700(red) nm The SSA values during."— Presentation transcript:

1 Wavelength dependence of the single scattering albedo Single scattering albedo (SSA) values at 450(blue), 550(green) and 700(red) nm The SSA values during the summer wet season show low SSA values (dark, absorbing aerosol) and little wavelength dependence The SSA values during two dust events in the winter dry season show higher SSA values and a very strong wavelength dependence. ( note that gaps in the data are when the absorption transmission dropped below 0.5) wet season dry season

2 Aerosol optical properties during two dust events on days 48 and 49, March Missing values for the single scattering albedo (SSA) are when the transmission was <0.5 for the aerosol absorption measurement. A strong anti-correlation is apparent with a decline in the SSA and increase in the Angstrom Exponent for smoke aerosol and an increase in the SSA and decline in Angstrom exponent for dust aerosol.

3 Frequency distribution of aerosol scattering coefficient in the dry season sub 10 um aerosol at 550 nm Jan – Mar 2006 ~73% of scattering is below 200 Mm -1. There are many episodes of high aerosol loading > 500 Mm -1 ~8% of scattering coefficient > 500 Mm -1

4 aerosol hygroscopic growth at AMF Niger Aerosol size Q1 dry season Q3 wet season Q4 dry season Sub micron1.18 (0.23)1.44 (0.29)1.31 (0.52) Sub 10 micron 1.01 (0.05)1.16 (0.10)1.05 (0.13) - Aerosol fRH is lower in the dry season when cloud processing is low and transport is from the north - The fRH increases slightly during the wet season when more clouds are present and long range transport is from the southwest. - Aerosol fRH is greater for submicron aerosol which is a mixture of both dust and combustion products from local burning -Overall, fRH is very low throughout the year -Values are not reported for Q2 when there were problems with the instrument, neph circuit board failure and flow controller malfunction

5 Summary Aerosol is nonhygroscopic, f(RH) = 1.0 Due to aerosol insolubility, CCN activation likely varies only with aerosol size with larger aerosol activating at a lower % super saturation. Dust absorption and single scattering albedo displays a strong wavelength dependence


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