Circulating factors rolein the climate warming of Siberia

On the territory of Siberia the changes of temperature field, activity of cyclones andanticyclones and also the circulation influence on the surface air temperature variability are investigated. The correlation between thevariability of circulation processes and the surface air temperature over Siberia for the period of current global warming (1976-2006) isanalyzed. For calculations of the temperature fields the daily mean temperature data at 169 stations, located on the territory of 50-70 °Nand 60-110 °E were used. The significant surface air temperature trends over this region were obtained: temperature increased by 1.1°Сfor the period of 1976-2006. It is shown that the positive trend of annual averaged surface air temperature is 0.36°C per every 10 yearswith higher values in some months. It was found that the rise in temperature occurs in February, March, October and May basically. It isrevealed that air pressure at this time was decreased by 0.18 hPa every 10 years. It means that decreasing of the anticyclonic activity, orstrengthening of the cyclonic activity, or both factors can cause warming on the territory of Siberia. For the analysis of the mesoscaleregional circulation the number of cyclones and anticyclones and the duration of their influence on the territory were investigated. Trajectoriesof moving and quantity of the cyclones and anticyclones of various geneses were analysed. The total variability of duration andinfluence on the territory of the cyclones and anticyclones for every month and year is submitted. The average annual duration of theanticyclones life in Siberia increases gradually to the end of the researched period. For studying the dynamics of cyclones and anticycloneson the territory of Siberia synoptic maps and the reanalysis data NCEP/DOE AMIP II have been used. Influence on the researchedterritory of cyclones and anticyclones in February, March, May and October was carefully investigated. It was determined thatsurface air temperature increase in February and March is caused by the intensification of the cyclonic activity. The increase of monthlyaverage temperature values for May and October is caused due to two factors: radioactive (the increase of anticyclonic circulation duration)and advective (warm air transfer). The number of cyclones in Siberia during the period of 1976-2004 and the number of the tropicalcyclones in the Northern hemisphere was compared. It is supposed that tendencies of the cyclonic and anticyclonic activity in Siberiaprobably are a part of the process of activisation of the global southern circulation, which was discovered in the second half of the 20thcentury for all the Northern hemisphere. The active tropical cyclogenesis influences the circulating processes of moderate latitudes essentially.

Keywords

Authors

References