Volume 26, Issue 80 (3-2026)
jgs 2026, 26(80): 20-35 |
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Hedjazizadeh Z, karbalaee A, fatahian M. (2026). Analysis of Decadal Variations in Geopotential Pressure over the Territory of Iran. jgs. 26(80), 20-35. doi:10.61882/jgs.26.80.15
URL: http://jgs.khu.ac.ir/article-1-4448-en.html
URL: http://jgs.khu.ac.ir/article-1-4448-en.html
1- , hedjazizadeh@yahoo.com
Abstract: (1803 Views)
This study investigates the spatial dynamics of the subtropical anticyclone over Iran during boreal summer, using daily ERA5 reanalysis data (1980–2020) and the Getis-Ord Gi* statistic to identify statistically significant hotspots (p < 0.01) in 500-hPa geopotential height (Z500) anomalies for June–August. Results reveal that the peak statistical hotspot occurs in July: a prominent warm cluster with Z-scores up to +4.1 (99% confidence level) forms over southwestern Iran (27°–32°N, 48°–60°E), reflecting the strongest positive departure from the long-term Z500 climatology. Conversely, a cold cluster with Z-scores reaching −10.2 emerges over the northwest (West Azerbaijan and Kurdistan provinces)—the lowest value recorded over the entire period—indicating pronounced geopotential depression driven by the orographic influence of the Alborz–Zagros ranges and incursions of mid-latitude systems. Histogram analysis of Z-scores confirms a distinctly bimodal distribution in July, with high frequencies in the [+2.5, +4.1] and [−10.2, −2.5] ranges and a pronounced trough near Z ≈ 0, underscoring strong spatial segregation between warm and cold clusters. Notably, the eastern half of Iran (central and eastern regions) consistently lacks significant hotspots across all three months, suggesting the presence of a dynamic transition zone shaped by the competition between subtropical and mid-latitude circulations. In August, although absolute Z500 exceeds 5890 m, the Z-score diminishes (+4.0), indicating that cumulative surface heating elevates the mean geopotential height—but its anomalous intensity relative to climatology weakens compared to July. Collectively, these findings suggest that the dynamical peak of the Iranian subtropical high lags the peak of surface heating by approximately one month.
Keywords: Summer high-pressure system, Hotspot analysis, Iran, Geopotential height anomalies, Percentiles, Subtropical anticyclone
Type of Study: Research |
Subject:
climatology
References
1. حجازیزاده، زهرا؛ 1372. بررسی سینوپتیکی نوسانات فشارزیاد جنب حاره. رساله دکتری جغرافیای طبیعی. دانشگاه تربیت مدرس تهران، استاد راهنما؛ هوشنگ قائمی.
2. حلبیان، امیرحسین؛1390. نقش پرفشار جنب حاره آزور در توزیع مکانی بارش های روزانه ایران، پژوهش نامه جغرافیایی، 1: 21-1.
3. زریّن، آذر؛ 1386. تحلیل پرفشار جنب حاره تابستانه بر روی ایران. رساله دکتری جغرافیای طبیعی. دانشگاه تربیت مدرس
4. تهران، استاد راهنما؛ هوشنگ قائمی.
5. زرین، آذر؛ مفیدی، عباس؛1390. آیا پرفشار جنب حارهای تابستانه بر روی ایران زبانهای از پرفشار جنب حارهای آزور
6. است؟ «بررسی یک نظریه»، یازدهمین کنگره انجمن جغرافیدانان ایران- 24 و 25 شهریور ماه 1390-دانشگاه شهید بهشتی،
7. صص 15-1.
8. زرین، آذر؛ داداشی رودباری، عباسعلی ؛1400. پیشنگری همادی نمایههای خشکسالی در ایران مبتنی بر برونداد چند مدلی CMIP5.
9. سلیقه، محمد؛1382. مدل سازی اثرهای آب و هوایی کم فشارهای حراراتی در منطقه جنب حاره، فصلنامه تحقیقات جغرافیایی، 70: 90-74.
10. علیجانی، بهلول؛ 1376. آب و هوای ایران. انتشارات پیام نور، صص230.
11. علیجانی، بهلول؛ 1378. بررسی سینوپتیکی سطح 500 هکتوپاسکال خاورمیانه در دوره 1990-1961، مجله نیوار، شماره 45-44، صص29-7.
12. عساکره، حسین؛ 1386. کاربرد رگرسیون خطی در تحلیل روند دمای تبریز. تحقیقاتجغرافیایی، شمارهپیاپی87، صص25-39.
13. عساکره، حسین؛ 1392. تحلیل روند موسمهای خشک و تر در شهر زنجان. جغرافیا و توسعه، شماره31، صص 49-48.
14. عساکره، حسین ؛ قائمی، هوشنگ و فتاحیان، مختار ؛ 1395. اقلیم شناسی مرز شمالی پشته پرفشار جنب حاره بر روی ایران، نشریه پژوهشهای اقلیم شناسی، سال هفتم، 25 و26: 35-5.
15. علیپور، یوسف؛ حجازیزاده، زهرا؛ اکبری، مهری و سلیقه، محمد؛ 1397. بررسی تغییرات پرفشار جنب حاره تراز 500 هکتوپاسکال نیوار ایران با رویکرد تغییر اقلیم، مجله مخاطرات محیطی، دوره هفتم، 18: 16-1.
16. علیجانی، بهلول و همکاران؛ 1398. رفتارسنجی اثر گرمایش جهانی بر پرفشار جنب حاره. پژوهشهای جغرافیای طبیعی، شماره 1، صص 50-33.
17. قائمی، هوشنگ و همکاران؛ 1388. تحلیل الگوی فضایی پرفشار جنب حاره بر روی آسیا و آفریقا. فصلنامه مدرس علوم
18. انسانی، شماره1، صص 224-223.
19. Agee, E. M., 1991. Trends in cyclone and Anticyclone Frequency and Comparison with
https://doi.org/10.1175/1520-0442(1991)004<0263:TICAAF>2.0.CO;2 [DOI:10.1175/1520-0442(1991)0042.0.CO;2]
20. Periods of Warming and Cooling over the Northern Hemisphere. Journal of Climate, 4,263-2267.
21. Bell, G. D., and Boast, L. F., 1989. A 15-year climatology of northern hemisphere 500 mb closed
https://doi.org/10.1175/1520-0493(1989)117<2142:AYCONH>2.0.CO;2 [DOI:10.1175/1520-0493(1989)1172.0.CO;2]
22. cyclone and anticyclone centers. Mon. Wea. Rev., 117, pp. 10-198.
23. Barry, R. G., and Carleton, A. M., 2001. Synoptic and Dynamic Climatology. Routledge, PP386.
24. Barry, R. G., Carlton, M., 2001.Synoptic and Dynamic Climatology, Shubhi Publications
25. London, London.
26. Cherchi, A., Ambrizzi, T., Behera, S., Carolina, A., Morioka, Y, and Zhou, T.,.2018. The
27. Response of Subtropical Highs to Climate Change
28. Davis, R. E., Hayden, P., Gay, A., Phillips, L., and Jones, V., 1997. The North Atlantic
29. Subtropical Anticyclon.Journal of Climate, Vol. 10 , pp. 278-744.
30. Galarneau, T., Bogart, F., and Aiyyer, R., 2006. Closed Anticyclones of Subtropical and
31. Midlatitudes" A 54-y Climatology (1950-2003) and three case Studies" , Submitted to J. Climate,
32. NO.55, pp.349-392.
33. Harris, M. F. G., 1962. Finger and steels. Diurnal variation of wind, pressure and temperature in
34. the troposphere and stratosphere over the Azores", Journal of the Atmospheric Sciences, volume
35. 19:136-149.
36. Hoskins, B., 1996. on the existence and strength of the summer subtropical anticyclones:
37. Bernhard Hurwitz memorial lecture. Bulletin of the American Meteorological Society, 77, 1287-
38. Lydolph, P., E., 1977, Climate of the Soviet :union:, in: World Servey of Climatology, Vol.7, Elsevier Scientific Pub, 362pp
39. Liu, Y. M, Wu, G. X., Liu, H., and Liu, P., 2001. Condensation heating of Asian summer monsoon
40. and the subtropical anticyclone in the Eastern Hemisphere. Climate Dynamics, 17,327-338 [DOI:10.1007/s003820000117]
41. Lu, R., and Dong, B., 2001. Westward extension of North Pacific subtropical high in summer. [DOI:10.2151/jmsj.79.1229]
42. Journal of the Meteorological Society of Japan, 79, 1229-1241.
43. Lee, S. K., Enfield, D. B., and Wang, C., 2011. Future impact of differential Interbasin Ocean
44. warming on Atlantic hurry-canes. J. Climate, 24, 1264-1275.
45. Mason, R. B. and Anderson, C.E., (1963). the Development and Decay of the 100 mb Summertime Anticyclone over Southern Asia". Monthly Weather Review, 93, 3-12.
https://doi.org/10.1175/1520-0493(1963)091<0003:TDADOT>2.3.CO;2 [DOI:10.1175/1520-0493(1963)0912.3.CO;2]
46. Natalie, A. F., J. B., Erik, T. S., and David, M. S., 2021. The Influence of South Pacific Convergence Zone Heating on the South Pacific Subtropical Anticyclone. Journal of Climate, Volume 34, Issue 10, p.3787-3798 [DOI:10.1175/JCLI-D-20-0509.1]
47. Snead, R. 1988. Weather Pattern in Southern West Pakistan. Archives for Meteorology, Geophysics, and Bioclimatology, Series B, Vol.16: 316-346. [DOI:10.1007/BF02243179]
48. Santos, J. A., Corte-Real, J., and Leite, M., 2005. Weather Regimes and Their Connection to the Winter Rainfall in Portugal, International Journal of Climatology, Vol.25, pp. 33-50. [DOI:10.1002/joc.1101]
49. Sukarni S. M., 2010. The influence of subtropical high-pressure systems on rainfall and temperatre distribution in Suriname and implications for rice production in the Nickerie District. Thesis for: Master of Science Natural Resource and Environmenta -Climate Change, 88pp.
50. Thomas, L., Gerald, E., and Celestino, |F., 2010. Projection of suitable habitat for rare species under global warming scenario. American journal of botany, 97(6):970-987. [DOI:10.3732/ajb.0900329] [PMID]
51. Tivig, M., Verena, G., Viju. O. J., and Stefan, A. B., 2020. Trends in Upper-Tropospheric
52. Humidity: Expansion of the Subtropical Dry Zones? Journal of Climate, 33 (6). pp. 2149-2161.
53. Wu, G. X., Liu, Y., and Liu, P, 2004. Formation of the Summertime Subtropical Anticyclone. [DOI:10.1142/9789812701411_0014]
54. East Asian Monsoon (World Scientific Series on Meteorology of East Asia), Chang, C. P., Ed.,
55. World Scientific Publishing Company, 560.
56. Wu, B., Zhou, T., and Liu, T., 2017. Responses of the summertime Subtropical Anticyclones to Global Warming, Climate Dyn., 49, 6465-6479. [DOI:10.1175/JCLI-D-16-0529.1]
57. Zaitchik, B. F., Evans, J. P., and Smith, R. B., 2007, "Regional impact of an elevated heat source: the Zagros Plateau of Iran". Journal of Climate, 20, 4133-4146 [DOI:10.1175/JCLI4248.1]
58. ZZarin, A., Ghaemi, H., Azadi, M., and Farajzadeh, M., 2010, Analysis of the spatial pattern of summertime subtropical anticyclones over Asia and Africa, A Climatological Review, Journal of Climatology, 30(2): 159-173. [DOI:10.1002/joc.1879]
59. Zhu, X., Dong, W., Wei, Z., Guo, Y., GAO, X., Wen, X. and Chen, J., 2018. Multi‐decadal
60. evolution characteristics of global surface temperature anomaly data shown by observation and CMIP5 models, International Journal of Climatology, v. 38(3), p. 1533-1542. [DOI:10.1002/joc.5264]
61. Nie, J., Fang, J., & Yang, X. Q. (2023). The mechanisms of the subseasonal zonal oscillation of the western Pacific subtropical high in 10-25-day period and 25-50-day period. Climate Dynamics, 60(11), 3485-3502. [DOI:10.1007/s00382-022-06523-7]
62. Fatahian, M., Hejazizadeh, Z., Karbalaee, A. R., Shahidinia, H., & Wang, J. (2025). Spatio-Temporal Analysis of Changes in the Iranian Summer Subtropical High-Pressure System from a Climate Change Perspective. Atmosphere, 16(3), 273. [DOI:10.3390/atmos16030273]
63. Chen, H., Xu, H., Ma, J., & Deng, J. (2022). Why is the mid-tropospheric North Atlantic subtropical high much stronger than the North Pacific subtropical high in boreal summer?. Climate Dynamics, 59(5), 1883-1895. [DOI:10.1007/s00382-021-06074-3]
64. Alijani, B., Toulabi Nejad, M., & Karbalaie Darei, A. (2019). Investigating the effects of global warming on subtropical high pressure. Physical Geography Research, 51(1), 33-50.
65. Li, W., Li, L., Ting, M., & Liu, Y. (2012). Intensification of Northern Hemisphere subtropical highs in a warming climate. Nature Geoscience, 5(11), 830-834. [DOI:10.1038/ngeo1590]
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