analysis of the relationship between synoptic patterns pollutants of dust and carbon monoxide in the shiraz city

1. introduction while human habitation was formed as concentrated and stable communities, air pollution had become perceptible on human life. by passing of time and the improvement of thriving and particularly by the industrial revolution commencement, air pollution gradually has converted into an international issue, principally in the present times (ghanbari and azizi, 1388: 16). whereas air pollution is one of the most significant risks to human; especially in metropolises, the investigation of its impacts is one of the primary priorities in climate researches. meteorology cannot connive at atmospheric pollution. nowadays, pollutant concentrations are developed threateningly by the urbanization growth and the improvement of living standards and industrial development. human adds to the increase in air pollutants by their activities and make survival difficult for themselves and other organisms. besides, they have applied changes in weather patterns of planet earth and environment and cause disorders in them. meteorological conditions and physical and dynamic features alterations of atmosphere play a critical part on air pollution levels. on the issue of the dispersion and transport of air pollution, the most significant causing factors include the winds of earth surface and low levels of the atmosphere as well as the vertical temperature gradients, which are determining elements in the upward movements and the pollutants vertical distribution in the atmosphere (ranjbar and mohammadian, 1389: 112). with regard to the fact that the main goal of the synoptic studies is to explain the key interactions between the air-sphere and the surface environment (yarnal, 1385: 1); in this paper, the determination and identification of influential synoptic patterns on the pollutant days in the categorization of environmental to circulation, as well as the quantity and procedure of the annual sulfur dioxide, carbon monoxide and particulate matter polluters were investigated in shiraz city. 2. study area shiraz is located in the south of iran and, is located in latitude 29 degrees, 36 minutes north and 52 degrees of 33 minutes of east longitude. it is built in a green plain at the foot of zagros mountains 1500 meters, (4900 feet) above sea level. fifth most population city of iran and the capital of fars province, in 2009 the population of city was 1455073. 3. material and methods for the investigation of urban pollutants situation, data and statistics of air pollution were achieved from the environmental protection organization of fars province to perform this research; and according to the air quality standards table the standard level of pollutants were indicated. through excel software application, polluted days were filtered and drew out. with regard to the fact that the main goal of this research is to identify the influential synoptic patterns on the quantity of particulate matter and carbon monoxide pollutants as well as polluted days; as a result, hourly and daily pressure data of open seas level (standard), the height of levels 500 and 850 hpa, the temperature of level 1000 as well as the omega of 850-hpa of the considered days (polluted days) were obtained from the website of the national center of environmental prediction and national center of meteorological research (ncep / ncar). they were mapped and analyzed in the grads software environment. in addition, the psi pollution standards index was applied to indicate the amount of pollutants. 4. results and discussion in the sum of 2247 days in the staff measurement station for particulate matter and carbon monoxide pollutants, 410 and 152 days were diagnosed as polluted, respectively. in addition, the investigations demonstrated that the greatest level of the particulate matter pollutants are related to july, which is 216/30(µg/m3) and the carbon monoxide pollutants highest level are related to september, which is 6/41(ppm). with regard to the fact that the synoptic systems of air-sphere set the boundary layer, in high-pressure system the inversion layer surface is pulled down and as a result, the boundary layer depth is decreased. this is owing to the downward subsidence of the air of free air-sphere (fa) and non-penetrating of it into the boundary layer which is caused by the existence of the strong covering inversion layer. consequently, air pollutants are confined in shallow boundary layer and lead to air stability as well as the air pollution occurrence (falah qalhary, 1389: 3). according to the index of psi pollution standards, the numbers which are higher than (psi > 100) are assumed as polluted day. in conformity with the coherence and continuity of polluted days, among 410 polluted days for particulate matter pollutants, four summer patterns were detected and among 152 polluted days for carbon monoxide pollutants, one winter pattern was detected. 5. conclusion the existence of a stack height (anticyclonic) at 500 hpa level was observed in the synoptic maps during the investigation period in all four summer patterns. the anticyclonic position in model (a) includes the extent of the red sea, higher than the latitude of 20 degrees north to the center of iran. the arabian peninsula center is the location of anticyclone center. in model (b), the anticyclone with closed contour of 5875 geopotential meters is located in southeast of iran and southern coasts of oman. however in pattern (c) the existence of deep ascending is observed and includes the anticyclone position of the arabian peninsula to the west coast of the red sea. in model (d), the anticyclonic center with the closed contour of 5910 geopotential is located in saudi arabia, on the subtropical high pressure position. generally, at the level of 500 mg, the variations of the anticyclone position between synoptic patterns in warm period, three models are placed in saudi arabia. therefore, model (b) is the only model which is located on the east of iran. while with the absence of these conditions in the cold period, the state of full-orbital is predominant. at the level of 850 hpa, the cyclonic conditions are predominant. the organization of pressure patterns in sea level is associated with the predominance of low pressure condition. the contour which is isotherms of 40 ° c is the witness for the thermal nature of this system. whereas in winter patterns, contrary to the summer patterns, at the level of 850 hpa, the spatial organization of the anticyclonic is predominant. furthermore, the existence of tab system pressure at sea level is the evidence for the complete coordination of the full height system location at high levels of air-sphere and pressure system at sea level. by shoaling the boundary layer, this factor will cause the confinement of pollutants close to the earth surface and the growth of pollutants concentration, in the anticyclonic conditions during the cool season.