Atmospheric circulation of the excessive moist and dry periods in the Ob-Irtysh interfluve

The variability of precipitation results from the specific character of atmosphere circulation, which interacts with the underlying surface. The present work contains the analysis of the relation between the anomalies of annual precipitation totals, warm and cold periods in the Ob-Irtysh interfluves, the forms of atmosphere circulation by G.Ya. Wangenheim - A.A. Girs, Ye.N. Blinova zone circulation index (I_Б) and North-Atlantic variation (I_NAO) in the 20 - 21 centuries. To reveal anomalously humid and dry periods, the long-term observation data collected from 17 meteorological stations located in the south-east of Western Siberia (southern taiga, forest-steppe and steppe areas) in 1936-2006 were used. The year (and year periods - warm and cold) was characterized excessively humid if the precipitation total exceeded 120% from average perennial index (∑ О > 120% ), and dry if the precipitation total was 80% and below average perennial index (∑ О ≤ 80% ). Precipitation anomalies were calculated regarding the average perennial index computed for the period under study (1936-2006). The correlation analysis between W, E, C circulation forms and precipitation anomalies at I_NAO >0 and I_NAO <0 in southern taiga and steppe varied a lot from month to month. The strongest relation of the formation of the anomalously humid cold periods in the area under study was observed at I_NAO <0 under the development of W and C circulation forms. The strongest relation of the formation of the anomalously dry cold periods was registered under the development of E circulation form. The strongest relation of the formation of the anomalously humid warm periods in southern taiga was observed at I_NAO > 0 under the development of W and E circulation forms. The strongest relation of the formation of the anomalously humid warm periods in steppe was observed at I_NAO >0 under the development of E circulation form. The dry warm periods in the area under analysis were registered at I_NAO >0 under the development of C circulation form.

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