Fig. 4. Calculated extinction coefficients for International Code 1 (R,„ — 0.1 km) and Code 5 (R,„ = 3 km) fogs. models used in the heterogeneous areosol calculations were taken from Nilsson (16). Comparisons were made between homogeneous (water mode) and heterogeneous particle (accumulation mode and coarse particle mode) models for two cloud types, cumulus and cumulonimbus, which are representative of cloud distributions having only small particles (a < 20 gm) and those having a significant fraction of larger particles with a > 20 gun (31). The presence of nuclei strongly influences the behavior at shorter wavelengths, whereas negligible differences exist between calculated coefficients at wavelengths longer than about 5 gtm. The extinction coefficient as a function of wavelength for A s 9 gun is relatively constant for homogeneous (water mode) particle calculations. For particle distributions with small-diameter nuclei (accumulation mode), however, the extinction coefficient decreases with decreasing wavelength for 2 s X < 5 gun. When the nuclei diameter increases, as with the coarse
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