The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Page 828
FIGURE Q.1 Calculated surface temperature
variation with changes in low-cloud cover and surface
albedo.
in the arctic region to promote ice melting and improved growing
conditions in Siberia. Before the more recent satellite
measurements, most of what was known about cloud processes and how
they contribute to the global radiative balance came from climate
modeling, and in climate models, most of the details of the cloud
processes were not included. Certainly, no individual clouds were
included on the grid scale of the general circulation models (GCM);
thus specific details of the microphysics, as it might involve
seeding or CCN, could not be studied within the concept of
GCMs.
Proposed Change in Low-Cloud Albedo
Through Emissions of Cloud Condensation Nuclei
In a recent paper, Albrecht (1989), following a hypothesis of
Twomey and Wojciechowski (1969), grossly estimated the additional
CCN that would be necessary to increase the fractional cloudiness
or albedo of marine stratocumulus clouds by 4 percent. He estimates
that this increase in low-level fractional cloudiness would be
equivalent to that attributed to a 30 percent increase in CCN. As
noted from Table Q.3, this 4 percent increase, if it were strictly
in lower-level cloud abundance at global average conditions
(35° latitude), would be more or less equivalent to the
cloudiness at 4° latitude further north. Albrecht's idealized
stratocumulus cloud, which he argues is typical, has a thickness of
375 m, a drizzle rate of 1 mm per day,
