علی قاسمی بگتاش

Today, there are many factors involved in air pollution. PM10 is one of the significant elements influencing air pollution in the city. Due to their fineness, these particles can travel to high altitudes and long distances. The metropolis of Tabriz is known as one of the polluted cities whose air pollution is caused by burning a huge amount of fossil fuels, lack of green space and topographic and climatic conditions. Given that the purpose of synoptic studies is to explain the key interactions between the atmosphere and the surface environment, and synoptic climatology pursues a major goal and that is to find the relationship between atmospheric circulation and the surface environment. Given the importance of the phenomenon of dusty air pollution and on the other hand its widespread spatial expansion in recent years in the northwest, the need for this research was felt more than ever; Therefore, in this study, suspended particles in the atmosphere have been analyzed as one of the most important air pollutants in Tabriz

In order to investigate the effect of active pressure patterns on pollution in Tabriz metropolis, the synoptic analysis method was used. In order to influence the meteorological conditions on increasing and decreasing pollution, pressure gauging meters have been used in connection with the main PM10 pollutant. To achieve this goal, the average daily data of PM10 in the years 1992-2010 in Bagh Shomal station and meteorological data of Hamidid station in Tabriz have been used. The method was as follows: the data were first entered into Excel software and based on the standard table of air quality, the standard limit of pollutants was determined. Extreme contaminated days were filtered and extracted by Excel. Polluted days with dangerous conditions on March 15-16, 2009 and to May 6 the same year. Then using the surface pressure data, the level of 500 hPa of pressure patterns on the infected far days were analyzed. The study of air quality index showed that the highest number of polluted days occurred in 2008 and the lowest number of dangerous polluted days occurred in 2006. In addition, the highest number of dangerous polluted days occurred in March, May, April and June. The results of the study of synoptic patterns show the existence of a weak pressure cells at the level of 500 and the dominance of a strong low pressure system at ground level and the distribution of temperature along with the hot core over the region. Also, the effect of the condition of the upper levels of atmosphere on the contaminated days by drawing synoptic maps of 500 hPa on the polluted days were examined. The Lund correlation method was used to select the representative days of the groups obtained from the classification of atmospheric pressure data. In this way, to select the representative day, the day that has the most similarity with the most number of group days was selected.

The correlation coefficient represents the degree of similarity of the patterns of the two maps with each other. To do this, a certain threshold correlation coefficient must be accepted. The value of correlation coefficient in such cases typically varies between 0.5 to 0.7. Representative days were extracted based on a threshold of 0.5. Thus, the day that has a correlation coefficient of 0.5 with more days was selected as the representative day. The 500 hPa pattern, which has changed the climate of Northwestern Iran, is a Rex-type blocking system. Such a system is called lateral lifting Rex. After re-combining the western current in the east of this system, hot and dry conditions are applied to the area under their coverage. From the Northwestern region of Iran, in the impact basin of the low eastern part of this Rex system, which is mentioned outside the combined flow; Therefore, the unstable conditions in the study area are due to the positive rotating tawny wind of this arrangement from the lateral Rex system.
In the case of west and east winds, the type of flow is important because their flow can be orbital or meridional. The wave motion of the winds in the meridional direction causes cold air to accumulate and fall inside the vessels within the higher latitudes to the lower latitudes, and vice versa, in the ridges, the warm air of the lower latitudes ascends to the higher latitudes. Orbital component maps show the direction of the wind (if the direction of the wind is negative and if it is positive in the direction of the west) and the speed of the orbital winds. The meridional component shows the wind speed in the north direction (if the wind speed values ​​are positive) and south (if the wind speed values ​​are negative). The wind map on the first day of pollution shows that the current The wind blows in a counter-clockwise direction in the low-lying center of the Mediterranean and at the same time in Northwestern Iran it moves in a counter-clockwise direction (anticyclonic) and increases pollution in the metropolis of Tabriz, but on the last day it gets west-east and The severity of pollution in Tabriz metropolis is gradually decreasing.

Given the importance of the phenomenon of dusty air pollution and on the other hand its widespread spatial expansion in recent years in the Northwest, the need for this research was felt more than ever; Therefore, in this study, suspended particles in the atmosphere, which is one of the most important air pollutants in Tabriz, has been analyzed. Examination of the air quality index of Bagh Shomal station in a period of study showed that the highest number of polluted days occurred in 2008 and the lowest number of dangerous polluted days occurred in 2006; but based on the persistence index and the average, days polluted with the dangerous condition of suspended particles were analyzed. According to the air quality index, the highest number of dangerously polluted days occurred in 2008 and in March, May and April. The hot core is on the area. Also, the effect of the condition of the upper levels of atmosphere was studied by drawing synoptic maps of 500 hPa on the polluted days. From the polluted middays, the two time periods of March 15 to March 17, 2008 and May 15 to May 17, 1988 were analyzed due to the continuity of the three days and the results indicated that there was a direct correlation between airborne synoptic circulation patterns and the polluted days in Tabriz. The main source of dust entering the metropolis of Tabriz during two periods with severe pollution of the deserts of Central Asia and Afghanistan. In addition this study showed that high air pressure, especially in the morning in autumn, causes an increase in the density of pollutants on the ground.

The issue of urban climate has been greatly addressed in the recent years. The migration of human beings to cities, along with the density of the residential units, the noise of urban vehicles and dangers of air pollution and many other things have had bad effects for the human beings like asthma, bronchitis, cardiovascular diseases, and skin cancer. The issue of air pollution is one of the main factors in urban climatology. The knowledge of climatology emphasizes on the effects of atmospheric pollution on the climate and vice versa. The investigation about the effects of air pollution on climate features has greatly been conducted in the east Iran. In the warm seasons of the year, especially in summer, Subtropical High pressure (STHP) covers large areas of lower, middle and upper levels of atmosphere. This extends vertically on top of the high pressure at 200 hp to 700 hp and results in a clear sky with no clouds and rain. Subtropical High Pressure (STHP) all over the country varies from one day to other day. In some areas it is very close to the earth surface, in the south east parts of Iran in some days it is about 2000 or 3000 meters above the earth surface and allows warm, low moist air. This situation sometimes spreads to northern Iran and causes monsoon rain with increase in temperature and decrease in air ascent. This means that when the height and activity of the STHP is high, there is suitable condition for clear sky and direct solar radiation. On top of the inversion water vapor content of the air is so low that it cant be measured. Subtropical system in high altitude is one of the reasons for the formation of deserts in Iran. Subtropical high is getting stronger with increasing height from the ground, while the polar high becomes weaker with increasing altitude.
As a matter of fact, mechanism for summer subtropical high pressure on Iran is a part of the Azores high pressure on the region. Thus, the above factors have caused the greatest events in the summer in Tabriz so that the city has experienced dangerous contaminants. With the beginning of autumn, the maximum and the minimum values of the dangerous contaminants was shifted compared with other seasons. However, in autumn there are dangerous infected cells in northern city of Tabriz in November and October, while in December the infected cells are in the center of Tabriz. The purpose of this study was to evaluate the frequency of Tabriz dangerous contaminants. For this purpose, the data of pm10 pollution index in the 8 years period (2005 to 2012) were evaluated by the Environmental Protection Agency in Tabriz (EPAT) for five stations of Baghshomal, RAhahan, Abrasn, Hakim Nezami, and Rastekhocheh. The index of this research is the day that the pm10 value of 420 is larger. The frequency and continuity of these dangerous days for each station were analyzed and investigated. In this study, we have used MATLAB for statistical analysis and SURFER for the mapping.
The results of the analysis have indicated that there were many dangerous air pollution events in summer in all stations with more dangerous contaminants in August as the highest frequency of the occurrence of dangerous infections.This indicates that formation of subtropical high pressure dominated on Tabriz play a key role in air pollution. However, in winter the occurrence of dangerous pollution has been reduced in most of the stations. Among the stations of this study, the stations of Baghshomal and Abrasan had the most dangerous pollution. The number of the days of infection in both stations has reached to more than 400 days during the study period. Furthermore, the results of the continuation of the dangerous contaminants of pm10 index indicate that more continuity of the pollution was in Baghshomal station and the lowest in Rahahan and Hakimnezami stations.
The spatial distribution of pollutant cells is varied in different months in Tabriz. However, based on PM10 density the dangerous pollution in most of the months has been formed in the city center. In January, February, June, September, October (multi-core) and December there were the core and the density of pollution in the city center. In March and August, the maximum contamination of Tabriz has been observed in the East. Intensity of infestation was observed only in April, July and November in west Tabriz while the maximum condensation has been observed in the northern and the southern parts of the Tabriz. Tabriz had no nuclei condensation of dangerous pollution in July.