Fig. 5. Calculated extinction coefficients for representative stratiform (solid curves) and middle-level (dashed curves) clouds. Particle distribution data were taken from the following references: altostratus, stratocumulus, and nimbostratus (Yamamotoet al. (32)]; altocumulus [Lewis (33)]; stratus I and II [Carrier et al. (34)]. particle mode, the extinction coefficients at shorter wavelengths increase in magnitude to values comparable to the water mode. Note that observational measurements do not show a decrease in jBex with decreasing wavelength as predicted by the accumulation mode, which may result from the assumption of constant-diameter nuclei. In addition, cloud-particle size distributions for a < 2 jim are not well defined due to the lack of adequate in situ measurement techniques. Since such small particles largely determine the absorption/scattering behavior at shorter wavelengths, calculational errors may be significant. Because of the uncertainties inherent in the heterogeneous particle models (especially at shorter wavelengths), we have shown the results of calculations for clouds
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