Iranian Journal of Geophysics

Iranian Journal of Geophysics

Climatology of fog in Iran based on observational data

Document Type : Research Article

Authors
Bahareh Taheri Aval Shahri 1
Abbas Mofidi 2
Abbasali Dadashi-Roudbari 3
Azar Zarrin 2
1 M.Sc. in Climatology, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Khorasan Razavi, Iran
2 Associate Professor, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Khorasan Razavi, Iran
3 Assistant Professor, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Khorasan Razavi, Iran
10.30499/ijg.2025.480760.1640
Abstract
This study investigated the climatology of fog in Iran. For this purpose, data from 73 synoptic meteorological stations over a 30-year period (1991-2020) were utilized for two variables: current weather conditions (fog identifier codes 40-49) and horizontal visibility. Initially, the frequency of fog occurrence was examined at both hourly (3-hourly) and annual scales for all stations. To investigate the spatial and temporal patterns of fog in Iran, relative humidity and the temperature difference between air temperature and dew point temperature were calculated using ERA5-Land reanalysis data. The geographical distribution of fog was assessed, and temporal trends in fog occurrence were examined. Two statistical measures, Sen's-slope and modified Man-Kendall, were used for this purpose. Furthermore, fog density was categorized into four main classes based on horizontal visibility and analyzed on both annual and hourly scales for all stations. Findings indicated that fog formation in all geographical regions of Iran is primarily a nocturnal phenomenon, occurring predominantly during nighttime hours and the early morning. The frequency of fog exhibited a diurnal trend, with a minimum at approximately 12:00 UTC and a maximum at approximately 03:00 UTC. Among the studied stations, those located in Ardabil Province and the southwestern region of the Caspian Sea (including Ardabil Airport, Ardabil, ParsAbad Moghan, Rasht, and Anzali) experienced the highest fog frequencies on both hourly and annual scales. The investigation into the spatial distribution of fog occurrence in Iran reveals that the foggiest regions of the country are located along a relatively narrow strip, extending from the southwest of the Caspian Sea to Dasht-e-Moghan in Ardabil Province. The main place of fog occurrence in Iran is Ardabil province, which has shown the highest frequency of fog occurrence in almost all hours of the day and night. Ardabil Airport, with an annual average of 120 foggy days and a peak of 57 occurrences at 03:00 UTC, was identified as the foggiest station in the country. In contrast, the results clearly showed that in the dry interior and eastern regions of Iran, both on an annual scale and on an hourly scale, fog formation is very limited and almost reaches zero in the middle hours of the day. Examining the concentration of fog shows that all four main categories of fog occur in Iran. Nevertheless, the occurrence of fog with moderate concentration is infrequent and is only limited to the southwest of the Caspian Sea and the Anzali station. The results also indicated that the most prevalent type of fog in Iran is thin fog, which prevails in the western regions and a significant portion of the country's interior. On the other hand, very dense fogs occur mostly in the southwest of the Caspian Sea and Ardabil province. A trend analysis of fog occurrence in Iran revealed that this phenomenon has a decreasing trend at 58% of the stations. Additionally, almost all major cities nationwide have experienced a decreasing trend in fog occurrences, which can be attributed to the shift in urbanization patterns over the past three decades. The results also indicated that the diversity of geographical and climatic features of Iran plays a key role in the spatial distribution of fog occurrence and its concentration.
Keywords
Fog, fog concentration, horizontal visibility, Iran, trend analysis of fog

Subjects

ارکیان، فروزان؛ صابری، تاتیس؛ اردکانی، حسین؛ زمانیان، محمدتقی. (1392). بررسی‌آماری و همدیدی وقوع رویداد مه در فرودگاه بین­المللی رشت. مجله پژوهش‌های علوم و فنون دریایی، 8(1)، 78-91.
پهلوان، راضیه. (1402)، مطالعه اقلیمی رخداد مه در فرودگاه رشت، نشریه پژوهش­های اقلیم شناسی، (53) 14، 215-224.
پهلوان، راضیه؛ مرادی، محمد؛ تاجبخش، سحر؛ آزادی، مجید؛ رهنما، مهدی. (1400). حساسیت­سنجی عددی دو رخداد مه در فرودگاه اردبیل به طرحواره­های لایه مرزی سیاره­ای با استفاده از مدل WRF . نیوار(45) 114و115، 70-83.
پهلوان، راضیه؛ مرادی، محمد؛ تاجبخش، سحر؛ آزادی، مجید؛ رهنما، مهدی. (1401-الف). مطالعه وضعیت اقلیمی مه در فرودگاه اردبیل در دوره آماری 2011تا 2020 . نیوار(46) 116و117، 1-12.
پهلوان، راضیه؛ مرادی، محمد؛ تاجبخش، سحر؛ آزادی، مجید؛ رهنما، مهدی. (1401-ب). بررسی اقلیمی مه در فرودگاه مشهد.13 (52)، 64-55.
زینالی، بتول؛ خلیلی­آذر، سیما؛ عینی، سعیده. (1397). پهنه­بندی مخاطرات جوی منطقه­ی شمال­غرب ایران. نشریه تحقیقات‌کاربردی علوم جغرافیایی، (53) 19، 177-193 .
تاجبخش، سحر. (1395). مطالعه آماری و شناسایی نوع مه به کمک یک الگوریتم در مهم­ترین فرودگاه­های کشور، پژوهش­های اقلیم­شناسی، 7(27 و 28)، 43-56.
تاجبخش، سحر؛ رهنما، مهدی. (1396). پایش و تحلیل رخداد مه به کمک داده­های زمینی و سنجش از دور. مجله علمی و ترویجی نیوار، 100و101، 35-44.
تاجبخش، سحر؛ مرادی، محمد؛ رشیدزاد، مهدی؛ محمدپور پنچاه، محمدرضا. (1397). پیش­بینی رخداد مه به‌کمک برخی روش­های تجربی‌ (فرودگاه­های تهران و مشهد). فیزیک زمین و فضا، 44(2)، 379-395.
سازمان مدیریت و برنامه‌ریزی استان‌ اردبیل، (1401). طرح‌ آمایش ‌استان اردبیل-‌تحلیل وضعیت اقلیمی.‌ شماره‌گزارش:502213AR002300301RE101971019، 74 صفحه.
شهبازی شیران، حبیب. (1372). جغرافیای اردبیل، جلد اوّل. انتشارات آرتا، اردبیل، ص 34.
صلاحی، برومند؛ محمدی، سیاوش. (1390). تحلیل همدید و آماری مه‌های فرودگاه اردبیل و ارائه­ی ساعات مناسب پروازی. پژوهش های جغرافیای طبیعی، 77، 69-92.
طاوسی، تقی؛ دل آرا، قدیر. (1389). پهنه بندی آب و هوایی استان اردبیل. نیوار، 71-70، 52-47.
مددی، محسن. (1391). مدیریت بحران برف و یخبندان در مناطق و شهرهای کوهستانی و برف­گیر. مجله علمی تخصصی برنامه ریزی فضایی، 1 (4)، 89-110
Ackerman, S., Knox, J. (2007). Meteorology: Understanding the Atmosphere. 2nd ed. Thomson Brooks, 502 p.
Ahmadi, H., Rostami, N., Dadashi-Roudbari, A. (2022). The impact of climate change on snowfall in Iran Basins using the satellite-derived snow products and CMIP6 bias-corrected model. Theoretical Applied Climatology, 151:603–618.
Akimoto, Y., and Kusaka, H. (2015). A climatological study of fog in Japan based on event data. Atmospheric Research, 151, 200-211.
Aksu, H. (2019). Event-Based Fog Characteristics of ÇARŞAMBA Airport. Applied Sciences and Engineering, 20(4), 515 – 523.
Belorid, M., Lee, C. B., Kim, J. C., & Cheon, T. H. (2015). Distribution and long-term trends in various fog types over South Korea. Theoretical and Applied Climatology, 122, 699-710.
Bergot, T., Guedalia, D. (1994). Numerical forecasting of radiation fog. part I: numerical model and sensitivity tests. Monthly Weather Review, 122, 1218-1230.
Bessho, K., Date, K., Hayashi, M., Ikeda, A., Imai, T., Inoue, H., Kumagai, Y., Miyakawa, T., Mutata, H.,Ohno, T., Okuyama, A., Oyama, R., Sasaki, Y., Shimazu, Y., Shimoji, K., Sumida, Y., Suzuki, M., Taniguchi, H., Tsuchiyama, H., Uesawa, D., Yokota, H., & Yoshida, R. (2016). An Introduction to Himawari-8/9 Japan’s New Generation Geostationary Meteorological Satellites. Journal of the Meteorological Society of Japan, 94(2), 151-183.
Byers, H. R. (1959). General Meteorology. McGraw-Hill Book Company Inc, New York, 540 p.
Croft, P.J., R. Pfost, R.L., Medlin, J.M., & Johnson, G.A. (1997). Fog forecasting for the southern region: A conceptual model approach. Weather and forecasting, 12(3), 545-556.
Dadashi-Roudbari, A., & Ahmadi, M. (2021). An assessment of change point and trend of diurnal variation of dust storms in Iran:
 
a multi-instrumental approach from in situ, multi-satellite, and reanalysis dust product. Meteorology and Atmospheric Physics, 133, 1523-1544.
DelSole T, & Tippett M. (2022). Confidence Intervals. In: Statistical Methods for Climate Scientists. Cambridge University Press, 52-68.
De Villiers, M.P., & van Heerden, J. (2007). Fog at Abu Dhabi International Airport. Weather, 62 (8),209-2014.
Forthun, G. M., Johnson, M. B., Schmitz, W. G., Blume, J., & Caldwell, R. J. (2006). Trends in fog frequency and duration in the southeast United States. Physical Geography, 27(3), 206-222.
Franca, G.B., Do Carmo, L.F.R., De Almeida, M.V., & Albuquerque Neto, F.L. (2018). Fog at the Guarulhos International Airport from 1951 to 2015. Pure And Applied Geophysics., 176, 2191–220.
Genon, L.M. (1987). Numerical Simulation of a Fog Event with a One-Dimensional Boundary Layer Model. Monthly Weather Review, 115, 592–607.
Georgil, J. J. (1940), Fog: its causes and forecasting with special reference to eastern and southern United States (I). Bulletin of the American Meteorological Society, 21, 135-148.
Gultepe, I., Tardif, R., Michaelides, S.C., Cermak, J., Bott, A., Bendix, J., Müller, M.D., Pagowski, M.,Hansen, B., Ellrod, G., & Jacobs, W. (2007). Fog research: A review of past achievements and future perspectives. Pure and Applied Geophysics, 164, 1121–1159.
Hamed, K. H., & Rao, A. R. (1998). A modified Mann-Kendall trend test for autocorrelated data. Journal of Hydrology, 204(1-4), 182-196.
Hanesiak, J.M., Wang, X.L. (2005). Adverse-weather trends in the Canadian Arctic. Journal of Climate, 18, 3140-3156.
Hardwick, W.C. (1973). Monthly Fog Frequency in the continental United States. Monthly Weather Review, 101, 763-766.
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., & Muñoz‐Sabater, J. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999-2049.
Hu, Z., Liu, S., Zhong, G., Lin, H., & Zhou, Z. (2020). Modified Mann-Kendall trend test for hydrological time series under the scaling hypothesis and its application. Hydrological Sciences Journal, 65(14), 2419-2438.
Hůnová, I., Brabec, M., Malý, M., Dumitrescu, A., Geletič, A. (2021). Terrain and its effects on fog occurrence. Science of the Total Environment, 768, 144359.
Johnson, R. P. (1941). Pliny, Natural History. With an English Translation in Ten Volumes. Volume III, Libri VIII-XI.
Johnstone, J. A., & Dawson, T. E. (2010). Climatic context and ecological implications of summer fog decline in the coast redwood region. Proceedings of the National Academy of Sciences, 107(10), 4533-4538.
Kampa, M., Castanas, E. (2008). Human health effects of air pollution. Environmental Pollution, 151, 362–367.
Khoury, D., Millet, M., Jabali., Y, & Delhomme, O. (2023). Fog Water: A General Review of its Physical and Chemical Aspects. Environment, 10(12) 224, 1-33.
Kim, Y., Hong, S. (2019). Deep Learning-Generated Nighttime Reflectance and Daytime Radiance of the Midwave Infrared Band of a Geostationary Satellite. Remote Sensing, 11(22), 2713, 1-14.
Kim, Y., Ryu, H.S., Hong, S. (2023). Data-to-data translation-based nowcasting of specific sea fog using geostationary weather satellite observation. Atmospheric Research, 290 (94), 106792.
Klemm, O., & Lin, N. (2016). What causes observed fog trends: air quality or climate change? Aerosol and Air Quality Research, 16(5), 1131-1142.
Koyuncu, R., Deniz, A., Ozdemir, E.T. (2019). Ankara Esenboga International Airport (Turkey) fog analysis and synoptical investigation of the fog event dated 17-19 December 2019. International Journal of Climatology, 42(16), 8368-8389.
LaDochy, S. (2005). The disappearance of dense fog in Los Angeles: Another urban impact? Physical Geography, 26, 177-191.
Lakra, k., Avishek, k. (2022). A review on factors influencing fog formation, classification, forecasting, detection and impacts. Scienze Fisiche e Naturali, 33 (2), 319–353.
Meyer, M.B., & LALA, G.G. (1986). FOG-82: A cooperative field study of radiation fog. Bulletin of the American Meteorological Society, 65, 825–832.
Muñoz-Sabater, J., Dutra, E., Agustí-Panareda, A., Albergel, C., Arduini, G., Balsamo, G., Boussetta, S., Choulga, M., Harrigan, S., Hersbach, H., & Martens, B. (2021). ERA5-Land: A state-of-the-art global reanalysis dataset for land applications. Earth system science data, 13(9), 4349-4383.
Muraca, G., Maviver, D.C., Auld, H., & Urquzio, N. (2001). The climatology of fog in Canada. Atmospheric Sciences. The climatology of fog in Canada, Proceeding of 2nd International Conference of Fog and Fog Collection, St. John’s, Newfoundland, 15–20 July, 2001.
Nakanishi, M., Niino, H. (2006). An improved Mellor-Yamada level-3 model: Its numerical stability and application to a regional prediction of advection fog. Boundary Layer Meteorology, 119, 397-407.
Neumann, J. (1989), Forecasts of fine weather in the literature of classical antiquity, Bulletin of the American Meteorological Society, 70, 46–48.
Odun-Ayo, I., & Alagbe, O. (2022). Fog computing technology: a review of current trends. The United Nations and Sustainable Development Goals, 261-275.
Ozdemir, E.T., Deniz, A., Sezen, İ., Menteş, S., Yavuz,V. (2016). Fog Analysis at Istanbul Ataturk International Airport. Weather, 71(11), 279-284.
Pagowski, M., Gultepe, H., King, P. (2004). Analysis and modeling of an extremely dense fog event in southern Ontario. Journal of Applied Meteorology and Climatology, 43, 3-16
Pauli, E., Cermak, J., Andersen, H., & Schütz, M. (2024). A satellite-based analysis of fog and low stratus life cycle processes in the Po valley, Italy (No. EGU24-15582). Copernicus Meetings.
Peace, R.L. Jr. (1969). Heavy-fog regions in the conterminous United States. Monthly Weather Review, 97, 116-123.
Perez-Díaz, J. L., Ivanov, O., Peshev, Z., Álvarez-Valenzuela, M. A., Valiente-Blanco, A., Evgenieva, T., Dreischuh, T., Gueorguiev, O., Todorov, P.V., & Aseashta, A. (2017). Fogs: Physical Basis, Characteristic Properties, and Impacts on the Environment and Human Health. Water, 9(10). 807.
Peterka, A., Thompson, G., & Geresdi, I. (2024). Numerical prediction of fog: A novel parameterization for droplet Ryu, H., Hong, S. (2020). Sea Fog Detection Based on Normalized Difference Snow Index Using Advanced Himawari Imager Observations. Remote Sensing, 12(9), 1-17.
Sarhan, E., Mofidi, A., Dadashi-Roudbari, A., Zarrin, A., & Minaei, M. (2024). Climatology of cold spots and LST minimums in Iran using high-resolution satellite data. Theoretical Applied Climatology, 155, 1395–1413.
Sen, P. K. (1968). Estimates of the regression coefficient based on Kendall's tau. Journal of the American Statistical Association, 63(324), 1379-1389.
Singh, M. K., & Gautam, R. (2022). Developing a long-term high-resolution winter fog climatology over South Asia using satellite observations from 2002 to 2020. Remote Sensing of Environment, 279, 113128.
Smith, D. K., Renfrew, I. A., Dorling, S. R., Price, J. D., & Boutle, I. A. (2021). Sub‐km scale numerical weather prediction model simulations of radiation fog. Quarterly Journal of the Royal Meteorological Society, 147(735), 746-763.
Stolaki, S.N., Kazadzis, S. A., Foris, D.V., & Karacostas, TH.S. (2009). Fog characteristics at the airport of Thessaloniki, Greece. Natural Hazards and Earth System Sciences, 9(5), 1541-1549.
Tardif, R., Rasmussen, R.M. (2007). Event-based climatology and typology of fog in the New York City region. Journal of Applied Meteorology and Climatology, 46 (8), 1141–1168.
Taylor, G. I. (1917), The formation of fog and mist. Quarterly Journal of the Royal Meteorological Society, 43(183), 241–268.
Van Oldenborgh, G. J., Yiou, P., & Vautard, R. (2010). On the roles of circulation and aerosols in the decline of mist and dense fog in Europe over the last 30 years. Atmospheric Chemistry and Physics, 10(10), 4597-4609.
Van Schalkwayk, L., Dyson, L.L. (2013). Climatological characteristics of fog at Cape Town International Airport. Weather Forecasting, 28(3), 631-646.
Velde, I.R. van der, G.J. Steeneveld, B.G.J. Wichers Schreur, A.A.M. Holtslag. (2010). Modeling and forecasting the onset and duration of severe radiation fog under frost conditions. Monthly Weather Review, 138(11), 4237-4253.
Wagh, S., Kulkarni, R., Lonkar, P., Parde, A. N., Dhangar, N. G., Govardhan, G., Sajjan, V., Debnath, S., Gultepe, I., Rajeevan, M. & Ghude, S.D. (2023). Development of visibility equation based on fog microphysical observations and its verification using the WRF model, Modeling Earth Systems and Environment, 9(1), 195-211.
Willett, H.C. (1928). Fog and haze: their causes, distribution, and forecasting. Monthly Weather Review, 56 (11), 435–468.
World Meteorological Organization. (2022). Fog Report, Available online:  https://cloudatlas.wmo.int/en/fog.html
Wright Jr, J. M. (1997). Federal Meteorological Handbook no. 3: Rawinsonde and Pibal observations. Office of the Federal Coordinator for Meteorology.
Yang, J.H., Yoo, J.M., Choi, Y.S. (2021). Advanced Dual-Satellite Method for Detection of Low Stratus and Fog near Japan at Dawn from FY-4A and Himawari-8. Remote Sensing, 13(5), 1-22.
Yang, Z., Wu, M., Xu, M., Zhu, X., Zhang, C., & Zhang, B. (2023). MoANet: A Motion Attention Network for Sea Fog Detection in Time Series Meteorological Satellite Imagery. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.
Yi, L., Li, M., Liu, SH., Shi, X., Li, K.F., & Bendix, J. (2023). Detection of dawn sea fog/low stratus using geostationary satellite imagery. Remote Sensing of Environment. 294(3). 766-771
Zarrin, A., & Dadashi-Roudbari, A. (2022). Spatiotemporal variability, trend, and change-point of precipitation extremes and their contribution to the total precipitation in Iran. Pure and Applied Geophysics, 179(8), 2923-2944.
Iranian Journal of Geophysics
Volume 19, Issue 5
November and December 2025
Pages 57-84