Growth of urban aerosol particles due to moisture absorption and its effect on horizontal visibility

Document Type : Research Article

Authors

Department of Space Physics, Institute of Geophysics, University of Tehran, Tehran, Iran.

Abstract

The size, chemical composition, and concentration of aerosols significantly impact horizontal visibility. The horizontal visibility can decrease due to the scattering and absorption of visible light by the particles and gases existing in the atmosphere. Horizontal visibility is influenced not only by aerosols but also by meteorological conditions—particularly relative humidity—which can impact visibility both directly and indirectly. Increased relative humidity significantly increases hygroscopic particles, thereby increasing the scattering cross-section and consequently reducing horizontal visibility. In some cases, changes in horizontal visibility are primarily determined by the concentration of PM2.5, meaning visibility can serve as an indicator of air quality. However, when relative humidity dominates changes in visibility, horizontal visibility may not be an accurate indicator of air quality. Overall, horizontal visibility is influenced by both human and natural factors. The concentration of suspended particles and relative humidity are key contributors to visibility changes, each with its own relative proportion. The relationship between PM2.5 concentration and horizontal visibility varies with relative humidity and requires further investigation. In order to examine factors such as the concentration levels of PM2.5 aerosols, and meteorological parameters including relative humidity, on the temporal changes in horizontal visibility in the metropolitan city of Tehran, which has distinct topography, daily average data from the Meteorological Organization's Mehrabad and Geophysics stations for variables like horizontal visibility, wind speed, relative humidity, temperature, and precipitation were collected. Also daily average pollutant data related to PM2.5 from Tehran’s Air Quality Control Center over a 10-year period (2013–2023) for the Sharif University and Tarbiat Modares stations, were collected. Although the Mehrabad and Geophysics stations are geographically close and share similar meteorological conditions, the characteristics of air pollution and atmospheric visibility in the two areas may differ due to different emission properties and levels of urbanization.
The results showed that increased relative humidity intensifies the impact of PM2.5 on visibility reduction, and at humidity levels above 90%, horizontal visibility significantly decreases with increased PM2.5 concentration. Additionally, a nonlinear negative relationship was observed between horizontal visibility, PM2.5 concentration, and relative humidity. Wind speed and average temperature play a positive role in improving visibility. As relative humidity increases, especially for greater values than 20 percent, the Volume Growth Fraction (VGF) of fine aerosols rises. Furthermore, at lower PM concentrations, VGF shows greater significance and variability, highlighting the role of other factors in moisture absorption by PM2.5 aerosols. It should be emphasized that the particle size distribution, the optical properties, and the chemical composition of aerosols also affect horizontal visibility. Therefore, the impact of aerosols and meteorological conditions on atmospheric visibility is relatively complex. This subject could be explored in future studies using a comprehensive numerical air quality model along with precise meteorological and environmental observations.

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References

اسفندیاری، س.، کمالی، ا. و باقری، س. (1392). تاثیر عوامل هواشناسی روی غلظت های دی اکسید گوگرد، دی اکسید نیتروژن و ازون در تهران. نشریه مدیریت و برنامه ریزی محیط‌زیست، 7(1392)، 61-70.
ثابت‌قدم، س.، احمدی گیوی، ف.، گلستانی، ی. و علی‌اکبری بیدختی، ع. (1392). ارتباط آلاینده‌های شهری با دید افقی منطقه تهران در سال 2008. فیزیک زمین و فضا، 39(4)، 109-122.‎
زارعی، ف.، قرایلو، م. و علیزاده چوبری، ا. (1396). تأثیر هواویزها بر بارش در شرایط رطوبت‌های نسبی متفاوت: مطالعه موردی. مجله ژئوفیزیک ایران، 11(2)، 135-155.‎
شرعی پور، ز. و علی اکبری بیدختی، ع. (1392). تغییرات دید جوی و عوامل مؤثر بر آن در ایستگاه ژئوفیزیک تهران طی دوره 10 ساله (2011-2001). مجله ژئوفیزیک ایران، 7(2), 128-141.‎
Alizadeh-Choobari, O., & Gharaylou, M. (2017). Aerosol impacts on radiative and microphysical properties of clouds and precipitation formation. Atmospheric Research, 185, 53-64.
Cheng, M. T., & Tsai, Y. I. (2000). Characterization of visibility and atmospheric aerosols in urban, suburban, and remote areas. Science of the total environment, 263(1-3), 101-114.
David, L. M., Ravishankara, A. R., Kodros, J. K., Venkataraman, C., Sadavarte, P., Pierce, J. R., Chaliyakunnel, S., & Millet, D.B. (2018). Aerosol optical depth over India. Journal of Geophysical Research: Atmospheres, 123(7), 3688-3703.
Deng, X., Tie, X., Wu, D., Zhou, X., Bi, X., Tan, H. & Jiang, C. (2008). Long-term trend of visibility and its characterizations in the Pearl River Delta (PRD) region, China. Atmospheric Environment, 42(7), 1424-1435.
Deng, J., Du, K., Wang, K., Yuan, C. S., & Zhao, J. (2012). Long-term atmospheric visibility trend in Southeast China, 1973–2010. Atmospheric Environment, 59, 11-21.
Deng, J., Xing, Z., Zhuang, B., & Du, K. (2014). Comparative study on long-term visibility trend and its affecting factors on both sides of the Taiwan Strait. Atmospheric research, 143, 266-278.
Doyle, M., & Dorling, S. (2002). Visibility trends in the UK 1950–1997. Atmospheric Environment, 36(19), 3161-3172.
Engelhart, G. J., Hildebrandt, L., Kostenidou, E., Mihalopoulos, N., Donahue, N. M., & Pandis, S. N. (2011). Water content of aged aerosol. Atmospheric Chemistry and Physics, 11(3), 911-920.
Hsu, C. H., & Cheng, F. Y. (2019). Synoptic weather patterns and associated air pollution in Taiwan. Aerosol and Air Quality Research, 19(5), 1139-1151.
Hu, Y., Yao, L., Cheng, Z., & Wang, Y. (2017). Long-term atmospheric visibility trends in megacities of China, India and the United States. Environmental research, 159, 466-473.
Hyslop, N. P. (2009). Impaired visibility: the air pollution people see. Atmospheric Environment, 43(1), 182-195.
Jiang, Y., Liu, C., Wen, C., & Long, Y. (2024). Study of summer microclimate and PM2.5 concentration in campus plant communities. Scientific Reports, 14(1), 3311.
Kathayat, B., Chapagain, N. P., & Lamsal, Y. R. (2022). Influence of ambient relative humidity on horizontal visibility in the two cities of western Nepal having contrasting urban-cum-industrial backgrounds and study of long-term variation. Journal of Nepal Physical Society, 8(1), 55-62.
Kreidenweis, S. M., Remer, L. A., Bruintjes, R., & Dubovik, O. (2001). Smoke aerosol from biomass burning in Mexico: Hygroscopic smoke optical model. Journal of Geophysical Research: Atmospheres, 106(D5), 4831-4844.
Löndahl, J., Pagels, J., Boman, C., Swietlicki, E., Massling, A., Rissler, J., Blomberg, A., Bohgard, M., & Sandström, T. (2008). Deposition of biomass combustion aerosol particles in the human respiratory tract. Inhalation toxicology, 20(10), 923-933.
Lee, J. Y., Jo, W. K., & Chun, H. H. (2014). Characteristics of atmospheric visibility and its relationship with air pollution in Korea. Journal of Environmental Quality, 43(5), 1519-1526.
Leung, D. M., Tai, A. P., Mickley, L. J., Moch, J. M., van Donkelaar, A., Shen, L., & Martin, R. V. (2018). Synoptic meteorological modes of variability for fine particulate matter (PM 2.5) air quality in major metropolitan regions of China. Atmospheric Chemistry and Physics, 18(9), 6733-6748.
Malm, W. C., & Day, D. E. (2001). Estimates of aerosol species scattering characteristics as a function of relative humidity. Atmospheric Environment, 35(16), 2845-2860.
Martonen, T. B., & Zhang, Z. (1993). Deposition of sulfate acid aerosols in the developing human lung. Inhalation toxicology, 5(1), 165-187.
Pendergrass, D. C., Shen, L., Jacob, D. J., & Mickley, L. J. (2019). Predicting the impact of climate change on severe wintertime particulate pollution events in Beijing using extreme value theory. Geophysical Research Letters, 46(3), 1824-1830.
Perkins, H. C. (1974). Air Pollution McGraw-Hill. London, Tokyo, Sydney.
Singh, A., Bloss, W. J., & Pope, F. D. (2017). 60 years of UK visibility measurements: impact of meteorology and atmospheric pollutants on visibility. Atmospheric Chemistry and Physics, 17(3), 2085-2101.
Seinfeld, J. H., & Pandis, S. N. (2016). Atmospheric chemistry and physics: from air pollution to climate change. John Wiley & Sons.
Sequeira, R., & Lai, K. H. (1998). The effect of meteorological parameters and aerosol constituents on visibility in urban Hong Kong. Atmospheric Environment, 32(16), 2865-2871.
Spichtinger, P., & Cziczo, D. J. (2008). Aerosol-cloud interactions–a challenge for measurements and modeling at the cutting edge of cloud–climate interactions. Environ. Res. Lett, 3(2), 025002.
Sun, X., Zhao, T., Liu, D., Gong, S., Xu, J., & Ma, X. (2020). Quantifying the influences of PM2. 5 and relative humidity on change of atmospheric visibility over recent winters in an urban area of East China. Atmosphere, 11(5), 461.
Tsai, Y. I., Lin, Y. H., & Lee, S. Z. (2003). Visibility variation with air qualities in the metropolitan area in southern Taiwan. Water, Air, and Soil Pollution, 144, 19-40.
Vaishali, Verma, G., & Das, R. M. (2023). Influence of temperature and relative humidity on PM2.5 concentration over Delhi. MAPAN, 38(3), 759-769.
Waggoner, A. P., Weiss, R. E., Ahlquist, N. C., Covert, D. S., Will, S., & Charlson, R. J. (1981). Optical characteristics of atmospheric aerosols. Atmospheric Environment (1967), 15(10-11), 1891-1909.
Wang, H., Xu, J., Zhang, M., Yang, Y., Shen, X., Wang, Y., & Guo, J. (2014). A study of the meteorological causes of a prolonged and severe haze episode in January 2013 over central-eastern China. Atmospheric Environment, 98, 146-157.
Watson, J. G. (2002). Visibility: Science and regulation. Journal of the Air & Waste Management Association, 52(6), 628-713.
Yang, Y. R., Liu, X. G., Qu, Y., An, J. L., Jiang, R., Zhang, Y. H., & Ma, Q. X. (2015). Characteristics and formation mechanism of continuous hazes in China: a case study during the autumn of 2014 in the North China Plain. Atmospheric Chemistry and Physics, 15(14), 8165-8178.
Ye, X., Tang, C., Yin, Z., Chen, J., Ma, Z., Kong, L., & Geng, F. (2013). Hygroscopic growth of urban aerosol particles during the 2009 Mirage-Shanghai Campaign. Atmospheric environment, 64, 263-269.
Zou, J., Lu, J., Wang, Y., Li, J., Liu, H., Wang, L., & Liu, W. (2021). Visibility Variation in Zhengzhou from 2008–2017. In IOP Conference Series: Earth and Environmental Science (631(1), 012034). IOP Publishing.
Journal of the Earth and Space Physics
Volume 52, Issue 1
online publication date: 30 May 2026
May 2026
Pages 89-106

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