FIGURE 3.25 Calculated ratio of transmission of UV and visible light to the earth's surface in the presence of aerosol particles compared to that with no aerosol particles for typical continental aerosol particles at (a) average summer RH and (b) high summer RH and for urban aerosol particles with (c) average RH and (d) high RH. (Adapted from Erlick and Frederick, 1998.)

downward-directed diffuse light), the light that has undergone diffuse reflection at the top of the cloud, and the light that has passed through the cloud, undergone reflection at the surface, and then been transmitted back upward through the cloud.

Table 3.14 shows the results of some of Madronich's calculations of the actinic flux enhancements for two cases of a collimated direct beam of light striking the top of a cloud, first under typical summer conditions at

TABLE 3.14 Calculated Enhancements or Depressions of Actinic Fluxes above and below Perfectly Light-Diffusing Clouds of Different Optical Depths"


Cloud optical depth

Above cloud

Below cloud


0.0 (clear sky; no cloud)

0 0

Post a comment