Ecoinformatics Problems of Global Climate Change - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 394

pro les of the west-eastern transport in the respective hemisphere and wave dis-

turbances superimposed on this transport. Their index determined (using a

respective normalization) as a coef first term of NAM expansion in

empirical orthogonal functions, can serve as the quantitative characteristic of the
modes. The presence of the positive NAM (or SAM) index denoted the existence of
a relatively strong west-eastern transport.
During the last years, it was recognized that dynamic factors contribute much to
observed temperature trends. For instance, in 1995 a marked similarity was
observed between the spatial distributions of the SAT

cient for the

fluctuations
for the last 30 years, with a clear increase of the NAM index. The increasing trend
of the index was accompanied by mild winters, changes of the spatial distribution of
precipitation in Europe, and the ozone layer depletion in the latitudinal belt >40

field and NAM fl

N.
Similar data are available for the Southern Hemisphere. The main conclusion is that
along with the ENSO event, both NAM and SAM are the leading factors of the
global atmospheric variability. In this regard, attention should be focused on the
problem of the 30-year trend of NAM towards an IM increase (after 1995 the index
lowered). It is still not clear whether this trend is a part of long-term oscillations.
Figure 5.12 represents NAM for the Northern Hemisphere. When there

°

cit
of air mass in the red areas, there tends to be a surplus in the blue areas, and vice
versa. At the same time, the jet stream winds tend to speed up or slow down in the
direction of the green arrows. A similar pattern exists in the Southern Hemisphere.

' sade

Fig. 5.12 The North Annular Mode pattern, which describes a large fraction of the monthly to
decadal changes in northern hemisphere climate (IPCC 2007)