the northern polar region and in the major part of the southern polar zone, the
positive pressure anomalies dominate again.
Comparison of Figs. 1 and 2 shows the similarity and fundamental differences of
the GAO structural features on the two time scales. In both cases, the GAO is
characterized by positive atmospheric pressure anomalies in the equatorial-tropical
region with its core in the Indian Ocean.
Though the inter-decadal GAO appears less intense in the terms of its anomalies,
it occupies a greater latitudinal belt. Moreover, the interannual GAO is characterized by a positive anomaly along its entire outer boundary, which in its turn is
adjacent to the region of low atmospheric pressure. Zones of high pressure are
sometimes observed at higher latitudes of both hemispheres. Otherwise in the
second case, low atmospheric pressure characterizes the whole area beyond the
central positive anomaly.
Fig. 2 The amplitude of the global atmospheric oscillation on inter-decadal time scale in the fields
of the atmospheric pressure anomalies at the sea level (top panel) and surface air temperature
(bottom panel)
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V. G. Neiman et al.