Ecoinformatics Problems of Global Climate Change - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 453

observed in March during the last decade, could result from radiative and chemical
processes, though a possible impact of other factors cannot be excluded.
A comparison of numerical modeling results for 1960 and 2000 revealed an
enhancement of downward

fluxes in the mesosphere in the period of cooling of the
lower stratosphere (in March in the Arctic and in October in the Antarctic). An
enhancement of downward

fl

fluxed (downwelling) in the mesosphere can be explained
as a response of gravity waves to wind intensi

fl

cation connected with a cooling of the
lower stratosphere. The downward shift of the enhanced downwellingwith a time shift
of about 1 month can be partially explained by the impact of planetary waves. An
enhancement of the dynamically induced warming connected with an enhanced
downwelling favors a limitation of stratospheric cooling and intensi

cation of the
circumpolar vortex in the lower stratosphere and, thus, favors an ozone layer recon-
struction due to such a feedback. Both in the Arctic and in the Antarctic a cooling due
to ozone depletion covers a region where polar stratospheric clouds (PSC) form in
spring, whose extent has increased between 1960 and 2000. The increase of PSC
amount could lead to ozone depletion in 2000 as revealed by calculations.
Based on the use of the NCAR CCM-3 (version 3) model, Kristjansson (2002)
obtained new estimates of the indirect climatic impact of sulphate and BC aerosol
due to the aerosol impact on cloud cover dynamics. Two versions of the aerosol
impact on clouds have been considered. One of them (the

first indirect effect or the
effect of radius) is connected with that the appearance of additional aerosol particles
as CCN leads to a decrease of the size of cloud droplets. The second indirect effect
manifests itself through a suppressed coalescence of droplets due to a decrease of
the size of droplets and hence, an increase of clouds lifetime (the effect of lifetime).
Both these effects raise the cloud albedo.
The global

fields of aerosol concentration have been simulated in Kristjansson
(2002) with the use of submodels of aerosol formation built in the climate model,
with the respective taken into account. Besides, characteristics of

background aerosol and the dynamics of the background aerosol size distribution
have been described. The droplets number density in liquid-water clouds was
calculated with the prescribed levels of oversaturation. The obtained size distri-
bution of cloud droplets and the outgoing SWR

“ life cycles ”

fl fluxes agree well with the results of

satellite observations.
With the use of the data on aerosol properties contained in IPCC-2001 Report, it
has been shown that in the case of global averaging a 5.3 % decrease of the cloud
droplets radius (by 0.58

m) and a 4.9 %
increase of cloud water content due to the impact of anthropogenic aerosol take place.
Maximum changes of these two parameters take place (by the order of their signif-
icance) in the regions of south-eastern Asia (here the content of sulphate aerosol is at
a maximum and the solar zenith angle is at a minimum), Northern Atlantic, Europe,
Siberia, and the eastern USA. Similar changes are also observed in the values of
indirect RF, whose global average value is

ʼ m for the average radius of droplets 10.31 ʼ

1.8 W m − 2 , with contributions of −

0.46 W m − 2 .
A repetition of the numerical experiment with the use of calculated data for
2100, according to the IPCC A2 scenario, has not changed the global average

changes of droplets ' radius and lifetime being, respectively, − 1.3 and −