Fig. 39

Size distribution of large and giant particles as a function of relative humidity according to A. Meszaros (1971). N„: concentration of particles with radius larger than the abscissa value. (By courtesy of Tellus)

that with increasing particle size the water soluble fraction of aerosol particles decreases, in accordance with direct chemical observations (E. Meszaros, 1968) and considerations on particle formation (Section 4.2). It should be also noted with respect to Fig. 40 that the results for 0.5 /¿m radius particle, are in good agreement with Hand's values (Hanel, 1970) derived from experimental data published by Winkler (1969).

Finally, we have to emphasize that the relationship between the relative humidity and particle growth is of importance for many atmospheric phenomena. Thus, the optical properties of the air and in consequence the atmospheric visibility vary as a function of relative humidity, owing to the variation of the scattering cross section of particles. This relation may be important even from the point of view of heat and radiation balance of the atmosphere, since tropospheric background particles consist mostly of water-soluble sulfate species.

r/r dry

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