The effect of Polar vortex and subtropical high pressure 500 hPa level to change the temperature of summer and winter in Iran

Document Type : Original Article

Authors

1 Ph.D., Tehran Khwarazmi University. Faculty of Geographical Sciences,

2 Assistant Professor, Department of Geography, Faculty of Command and Staff, Amin University of Police Sciences

3 Ph.D. in Geography and Urban Planning, Police Science Research Institute

Abstract

The polar vortex and Azores subtropical high pressure is considered the most obvious and permanent feature of the hemispheric circulation in the Northern Hemisphere, and the increase or decrease of their intensity index and expansion index at the level of 500hPa  pressure level is the main determinant of dry and wet periods in mid-latitudes and Iran. Therefore, the aim of this study is to explain the changes of these two systems in winter and summer. The maps and graphs of the monthly average of the polar vortex and the high pressure subtropical in Iran's atmosphere have shown significant changes in these two factors. The results showed that the surface and intensity index of the polar vortex had a downward trend and the representative of this system has regressed by about 2 degrees towards higher latitudes. The high-pressure indicators near the Azure tropics have been increasing in the summer season; So that in the last decade of studies, about 97 percent of the country's area has been under the control of this system, and the system's representative has progressed from the latitude of 36.15 degrees in the first decade to the latitude of 38.64 degrees in the last decade.

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