Different Climate Scenarios of the North Atlantic and Eurasia Regions

Since atmosphere pressure field is an actual envoy of climatic signal the atmospheric Highs and Lows should be attributed to the key active focal points within the ocean-atmosphere interplay system. Here we were set a task to determine how the dynamics of those centers of action relates to the climate change both on regional and global scales. It should be emphasized that for studying such kind of variability we decided to use a two-way state parameter emerged some kind of the North Atlantic Oscillation index. For this target the atmospheric pressure and near-surface temperature differences between the Azores High and the Icelandic Low for the period 1900-2012 within the spatial-temporal average-out (20º latitude, 20º longitude and 12 years) were considered. The secular term of phase states of the system under consideration was found divided into three nonintersecting subsets. Each of that was put in consequence with one of three climatic scenarios related to the periods of 1905-1935 (relatively warm phase), 1940-1970 (cold phase) and 1980-2000 (warm phase). A life time of such a scenario lasted about 20-35 years, and the transition from one scenario to another covered 2-3 years, i.e. it run comparatively quickly. Attached Fig. shows a phase trajectory of the thermo-baric index for the North Atlantic region. Different colorations mark three particular clusters each of which seems to correspond to a certain climate scenario. The revealed non-overlapping sub-aggregates of the thermodynamic parameters related to each particular climate scenario give an idea to follow the circulation peculiarities and the interrelated temperature differences within the limits of the Northern Atlantic ocean-atmosphere regional system. The results of this analysis bear evidence that the most probable intermittent strengthening and weakening of Hadley and Ferrell circulations occurred there in coincided phase. Therefore, in the beginning of the XX century (1905-1935) and its last quarter (1980-2000) a significant intensification of these general meridional circulation cells took place. Their weakening was traced in the middle of the last century (1940-1970), and can be also noticed in the beginning of the present century. The phases of strengthening and weakening of the atmospheric circulation longitudinal component in the Northern Atlantic are well correlated with the inter-decadal variations of the sea surface temperature in the tropical ocean area, which are, apparently, connected with the corresponding fluctuations of its thermohaline circulation. The analogous character of the climate system behavior was also detected in some other regional atmospheric activity centers that can be considered as a witness on the global nature of the detected phase type of modern climate inter-decadal variability. Thus, for instance, the thermo-baric phase trajectories, featuring the dynamics of the regional climate in Eurasia, also shows the hints of three scenarios presence, related to the periods of 1905-1935, 1940-1970 and 1980-2000 consequently. In this particular assessment the Siberian High and the depression on Hindustan peninsular were assumed as the regional key atmospheric activity centers. Hence, we have the grounds to suppose that mentioned above the short-period inter-decadal excitations of the modern climate have a global nature and are manifested everywhere. Finally, the attention should be paid to the fact that at the entry of XXI century the thermodynamic state of the Northern Atlantic regional climate system shows a tendency to face towards the situation, similar to the scenario of the 1940-1970.