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Showing 2 results for Vorticity
Investigating the variability of the Siberian high pressure intensity in relation to the anomalous winter circulation of the atmosphere
Atefeh Rezaei Talei, Zahra , Buhlol Alijani, Hematolah Roradeh, Taher Safarrad,
Volume 0, Issue 0 (3-1921)
Abstract
The role of regional and extra-regional forcings causes changes in the Siberian high-pressure cyclonic circulation every year. In this regard, an attempt was made to investigate the variability of the intensity of the Siberian high pressure in relation to the abnormal winter circulation of the atmosphere. For this purpose, gridded data of sea level pressure, geopotential height, orbital and meridional wind components of Center for Environmental Prediction/Atmospheric Sciences (NCEP/NCAR) between the years until 2020 (December to February) were used. After applying the Siberian high pressure intensity index, the extreme periods of this high pressure in winter were extracted. Next, the development of this system and the systems affecting the Siberian high pressure were investigated using the quantity of relative Vorticity advection. The results showed that during the winter period, the high pressure center of Siberia has undergone changes and has taken on a growing trend between 4 and 6 hectopascals. On the other hand, it was observed that the role of atmospheric systems such as dynamic ridges on the Siberian region along with advection The negative relative humidity, the location of the Siberian region in the east of the ridge, and the formation of omega bands play an important role in strengthening this system, which has caused this high pressure to develop from east to west or north to south. On the other hand, the role of the polar vortex in the cold advections of the region and the displacement towards the equator has caused the Siberian high pressure to sometimes increase by more than 11 hectopascals compared to its long-term average. Finally, it was observed that the atmospheric circulation in mid-latitudes plays a transitional role in the high pressure changes in Siberia and the polar and subpolar currents.

The studying and synoptic analysis of mechanical in mechanism of widespread winter precipitation of Iran
M Masoud Jalali, M Mehdi Doustkamian, A Amin Shiri Karim Vandi,
Volume 19, Issue 55 (12-2019)
Abstract
The aim of this study was to analyze the mechanism is precipitation Comprehensive Iran. For this purpose the daily precipitation data of 483 synoptic and climatology stations arranged. In this study, a comprehensive annual rainfall is said to have a minimum rainfall and above, 50% sequence coverage and have at least two days. Winter surround Iran on the condition of rainy days were extracted and examined. Then, to review and analyze the mechanism of atmospheric precipitation comprehensive synoptic and dynamic parameters such as moisture flux, vortices, ground level pressure, Geopotential, meridional and zonal wind component for the levels of 1000, 850, 700 and 500 HP studied and analyzed was. The results of this study showed that the widespread mechanism of dynamic and synoptic Winter country most affected by the composition of the atmosphere patterns such as the Mediterranean low pressure - low pressure core Persian Gulf, Iran, Central High East Europe closed low pressure, low pressure Urals - the Middle East, high pressure, low pressure Saudi Arabia - High pressure belt Europe and Siberia - Iran's low-pressure center. However most of the winter precipitation of moisture flux feed barley middle-Level interaction, particularly levels of 850 and 700 HP respectively. It was while change 500 hPa atmospheric dynamical mechanism is an important role in Iran's winter inclusive.


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