نوع مقاله : مقاله پژوهشی
نویسندگان
1 اداره کل هواشناسی استان مرکزی، اراک، ایران
2 پژوهشگاه هواشناسی و علوم جو، تهران، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction: Urbanization and air pollution, especially in megacities, are major issues today. Understanding the factors contributing to this problem is crucial, 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 research 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.
Material 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 mb levels, Era5 reanalyzed data with a resolution of 0.25 degrees extracted from the ECMWF database were used.
Results and Discussion: The results indicated 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 did not have a significant effect in reducing pollutants. The investigation of meteorological quantities in the upper levels of the atmosphere showed that the height of the boundary layer fluctuates between 200 and 1400 m daily, which was less than 400 m from late November to January. Analysis of the vertical velocity at altitudes of 825 and 700 hPa revealed a downward movement during winter, autumn, and spring, while an upward trend was noted during daytime hours in the summer season. Furthermore, a descent was observed at the 500 hPa level throughout all seasons during nighttime hours, which is not as effective as the other two altitude levels. Examining the daily air ventilation coefficient also indicated its high fluctuations throughout the year from 800 to 7500 m2s-1. The number of hourly changes also indicated fluctuation in the range of 22000 to around zero. The maximum ventilation coefficient at 12 UTC was between 3000 and 20000 m2s-1. At 00:00, 03:00, and 21:00 UTC, the ventilation coefficient was less than 1500 m2s-1 on all days of the year. Also, according to the location of Arak and Shazand, 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 at both 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.
کلیدواژهها [English]
)