Document Type : Original Article
Authors
1
markazi province meteorology office
2
Research Institute of Meteorology and Atmospheric Science
10.48308/envs.2024.1340
Abstract
Introduction: Urbanization and air pollution, especially in megacities, are major issues today. It's crucial to understand the factors that contribute to this problem, and reducing the associated risks is a top priority for city and country officials. Arak City in Iran is one of the most polluted cities in the country, with industrial activities being the main cause of pollution. This article aims to investigate the meteorological factors that contribute to the pollution potential of Arak City, including wind speed, temperature, pressure, precipitation, boundary layer height, vertical velocity of the atmosphere at the levels of 825, 700, and 500 mb, and air conditioning coefficient. The study ultimately confirms Arak City's reputation as one of the most polluted cities in Iran.
Materials and methods: In this article, from the 20-year statistics of the Arak observation station (1380-1399) for the quantities of the earth's surface, including wind speed, temperature, pressure, and precipitation, as well as the 20-year data from 2001 to 2020, the reanalyzed data of Era5 from the database ECMWF has been used for upper-level quantities. To check other atmospheric quantities, including boundary layer height, wind speed in the upper atmosphere, and vertical wind at 825, 700, and 500 millibar levels, Era5 reanalyzed data with a resolution of 0.25 degrees will be used daily, which is from the ECMWF database. has been extracted and examined.
Results and discussion: The results indicate that low temperatures in the cold period of the year, as well as low night and morning temperatures in the cold months of the year, can cause temperature inversion and increase the retention potential of atmospheric pollutants. The average wind speed indicates the low and insignificant effect of the wind, especially in the cold days of the year and in the morning and night hours. Daily per capita rainfall of less than 1 mm does not have a significant effect in reducing pollutants. The investigation of meteorological quantities in the upper levels of the atmosphere shows that the height of the boundary layer fluctuates between 200 and 1400 meters daily, which is less than 400 meters in late November to mid-Bahan. 500 mb showed that in the first months of spring and autumn and winter, we see atmospheric subsidence at the level of 825 and 700 mb, and at 00, 03 and 21 UTC on the hot days of the year, at the level of 825 mb. is showing. At the 500 mb level, there is a tendency to climb with small amounts, which is not as effective as the other two altitude levels. Examining the daily air ventilation coefficient also indicates its high fluctuations throughout the year from 800 square meters per second to 7500 square meters per second. The number of hourly changes also indicates fluctuation in the range of 22000 to around zero. The maximum ventilation coefficient at 12 UTC is between 3000 and 20000 m2/s. At 00:00, 03:00, and 21:00 UTC, the ventilation coefficient is less than 1500 square meters per second on all days of the year. Also, according to the location of Arak and Shazand and the study of the winds of these two cities, there is a possibility of the transfer of atmospheric pollutants from Shazand to Arak, especially in spring, autumn, and winter.
Conclusion: Overall, the study of weather patterns both at ground level and in higher parts of the atmosphere highlights the risk of pollution buildup and low ventilation in Arak City, particularly during the colder months and during nighttime and early morning hours. As a result, it is important for policies to prioritize the establishment of low-pollution industries and the management of sources of pollution, especially during the aforementioned times.
Keywords: Arak, Pollution Potential, ventilation coefficient, boundary layer
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