With a 6-channel integrating nephelometer spectral scattering properties of the atmospheric aerosol have been measured during the third part of the Atlantic Expedition 1969. A meridional cross section of light scattering integrals in the wavelength range 0.475 µm to 0.924 µm was recorded reaching from 10° S to 60° N along 30° W. With a new algorithm the time series of hourly scattering spectra was inverted yielding a first meridional cross section of the median radius of the number size distribution in situ. Three air mass regimes could be distinguished in the course of the experiment, the first one being the extremely clean air of the SE-trade south of the ITC. An abrupt increase in light scattering marked the hemispheric change when the ship entered the NE-trade which was heavily loaded with Sahara dust. North of the trade region the ship sailed through maritime North Atlantic air masses with highly variable light scattering and a slow decrease in median radius with latitude.

Latitude and Longitude are means for each day, estimated from cruise track

Supplement to: Heintzenberg, Jost (1977): Spectral light scattering and the atmospheric aerosol over the Atlantic. Meteor Forschungsergebnisse, Deutsche Forschungsgemeinschaft, Reihe B Meteorologie und Aeronomie, Gebrüder Bornträger, Berlin, Stuttgart, B12, 1-9