Groisman, P. Y., 1996: Assessing surface-atmosphere interactions
from the USSR standard meteorological network data. Part 2. Cloud and snow
cover effects, Journal of Climate (accepted).
Groisman and Genikhovich (1996) developed a method to obtain direct
estimates of surface turbulent heat fluxes. We now apply it to the territory
of the former USSR, using the 3- / 6-hourly data of 257 stations for the
past several decades to assess the sensitivity of sensible heat flux to
cloud and snow cover. This property was quantified for bare soil landscapes
over the entire country. During the day, the presence of clouds is associated
with low values of sensible heat flux from the surface to the atmosphere.
At night (and during the day in winter in high latitudes), the sign of
the effect is different, but because the direction of sensible heat flux
is also different (from the atmosphere to the surface), the presence of
clouds again reduces the turbulent heat exchange between the bare soil
and the atmosphere. The estimates of "overall cloud effect" on summer sensible
heat flux are compared with similar estimates from four general circulation
models (GCMs) to assess the abilities of these GCMs to reproduce the response
of this flux to cloud cover change.
Snow on the ground is associated with temperature depression. When the
effect of this depression is excluded, the presence of snow on the ground
generally is associated with less water vapor in the lower troposphere
under clear sky conditions while the evaporation rate and sensible heat
flux are higher than average.