Examining Trends of the Intensity of Mediterranean-Red Sea Cyclones

Document Type : Full length article

Authors

1 Department of Geography, Faculty of Human Sciences, University of Zanjan, Zanjan, Iran

2 Department of Geography, Faculty of Geography and Environmental Planing, University of Zahedan, Zahedan, Iran

10.22059/jphgr.2024.363162.1007785

Abstract

ABSTRACT
Among the cyclones that affect the sometimes-widespread rainfall in Iran are the merging systems of the Mediterranean and Red Seas. Therefore, it is very important to obtain the changes in the intensity of the geopotential height and the geopotential height shift of the Mediterranean-Red Sea convection patterns as one of the factors of the manifestations of these gyres, as well as the precipitation in some areas of Iran. To carry out this research, the data of geopotential height level of 1000 hectopascals related to the European Center for Medium-term Atmospheric Forecasting and ERA-Entrim version were used as a six-hour observation during the period of 1979-2018. To investigate the presence of jumps and fluctuations in the intensity of the Mediterranean-Red Sea cyclone centers during the statistical period, the Alexanderson index, known as the Standard Normal Homogeneity Test (SNHT) index, was used. A non-parametric chi-square statistic was exerted to verify and investigate the significance of the trend between geopotential height data and geopotential height tilt data. The parametric linear regression method was used to analyze and model the long-term trend. The findings of the present research indicate the increase of geopotential height in the place of the formation of the circulation centers of the Mediterranean Sea, as well as the decrease of the pressure gradient in the average annual values, which will probably lead to a decrease in instability and precipitation in the affected areas. The geopotential height shift data of the Mediterranean Sea had a significant jump in 1996, which divided the time series into two periods before and after the jump. The results indicate an upward trend in these two time periods, but the second period, with a gentler slope, has increased compared to the previous period
Extended Abstract
Introduction
Mediterranean Sea and Red Sea cyclones are a type of extratropical-tropical merge system that can influence precipitation over Iran. These combined Mediterranean-Red Sea cyclones form concurrently over the Mediterranean and Red Sea basins. They may sometimes merge as they track eastward, bringing precipitation to Iran (particularly southern and southwestern Iran). Changes in these merged cyclone systems are likely linked to shifts in Iran's precipitation climatology. Examining trends in the intensity of Mediterranean-Red Sea cyclones can thus provide insights into changes in Iran's precipitation patterns. This study investigates trends in the intensity of combined Mediterranean-Red Sea cyclonic systems and their relationship to precipitation over Iran. Cyclone intensity is assessed using geopotential height data at the 1000 hPa level over 40 years. Statistical tests, including chi-square and linear regression analysis, are applied to the geopotential height time series to detect significant trends. The focus is on examining changes in geopotential height slopes and trends that may indicate cyclone intensity changes. This research aims to improve understanding of how Mediterranean-Red Sea cyclones change and identify their impacts on Iran's precipitation climatology. The results can aid in tracking precipitation changes and projecting future climate scenarios for the region. The intensity trends may also provide broader insights into how climate change influences global cyclone behavior.
 
Materials and methods
To examine the changes in intensity of atmospheric systems and geopotential height, as well as the geopotential height shift of Mediterranean-Red Sea cyclones from 1979 to 2018, geopotential height data at the 1000 hPa level were utilized. The study area encompassed coordinates ranging from -10° E to 120° E and 0° N to 80° N, with a spatial resolution of 0.25° x 0.25°. This area consisted of 321 x 521 pixels, totaling 167,241 pixels. The Mediterranean and Red Sea cyclones, which are extratropical-tropical systems that occasionally merge and influence precipitation in Iran, were investigated. Statistical tests, such as chi-square and linear regression analysis, were conducted on the geopotential height time series for each pixel within the studied region to identify significant trends. The primary focus was analyzing changes in geopotential height slopes and trends, which could indicate cyclone intensity alterations.
 
Results and Discussion
This section presents the findings and discussion on the changes observed in monthly geopotential height intensity and geopotential height gradient of Mediterranean-Red Sea cyclones. In the Mediterranean Sea, an upward trend was observed in the geopotential height intensity, while a downward trend was observed in the geopotential height gradient. The increase in geopotential height over the circulation centers of the Mediterranean Sea and the decrease in pressure gradient are likely to result in reduced atmospheric instability and precipitation in the region. These results align with Darende's (2013) and Skleris et al. (2012) findings. Contrasting the Mediterranean Sea, the analysis of the Red Sea data revealed a downward trend in geopotential height and an upward trend in geopotential height intensity, indicating an increase in instability. This finding is consistent with the results of Asakereh and Khani (2021). No statistically significant trends were observed in the annual averages of geopotential height and geopotential height gradient in the Red Sea. However, the annual averages of both geopotential height and its gradient in the Mediterranean Sea exhibited a decreasing trend. A notable shift in the Mediterranean geopotential height occurred in 1996, dividing it into two distinct phases. Both phases showed an upward trend, albeit with a gentler slope in the second phase. The annual trend of geopotential height in the Mediterranean Sea revealed a decreasing pattern, which has been previously documented in studies by Alpert (1994, 2004). 
 
Conclusion
These studies suggest that while this reduction in geopotential height has taken place, cyclone tracks have shifted towards northern latitudes, resulting in increased drought and decreased precipitation in regions influenced by these cyclones, including Iran. The studies also acknowledge that changes in high-pressure systems near the tropics and alterations in cyclone direction contribute to variations in dry seasons and reduced precipitation. Further investigation of long-term changes in the geopotential height of the Mediterranean Sea identified three distinct phases in the time series: 1988-1979, 2005-1989, and 2006-2018. The decreasing trend in Mediterranean Sea cyclones persists until the final years of the period, indicating a potential cause for the reduction in atmospheric instability. The Kolmogorov-Smirnov statistical test was employed to determine the appropriate statistical test (parametric or non-parametric) for comparing means and variances across different periods. The parametric tests (one-sample t-test) and the one-way variance test confirmed the normal distribution of the data. Furthermore, no statistically significant trends were observed when examining the geopotential height intensity and gradient of two-day continuities of Mediterranean-Red Sea cyclones.
 
Funding
There is no funding support.
 
Authors’ Contribution
All of the authors approved the content of the manuscript and agreed on all aspects of the work.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.

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Main Subjects


  1. Alexandersson, H. (1986). A Homogeneity Test Applied to precipitation data. Journal of Climatology, 6, 661- 675.
  2. Alijani, B. (2013). iranian weather. Payam-Noor University Publications. [In Persion].
  3. Alizadeh, T., Azizi, K., Moheb, A., & KHoshakhlaq, F. (2016). Identification the Effect of Winter Temperature Changes on Cyclone Frequency and Intense in Mediterranean. Geography and Environmental Planning, 27(1), 217-232. doi: 10.22108/gep.2016.21367. [In Persion].
  4. Alpert, E., Neeman, B., & Shay-E1, Y. (1990a). Climatological analysis of Mediterranean cyclones using ECMWF data. Tellus, 42A, 65-77.
  5. Alpert, E., Neeman, B., & Shay-E1, Y. (1990b). Intermonthly variability of Cyclone tracks in the Mediterranean. J. Climate, 3,1474-1478.
  6. Amarouche, K., & Akpınar, A. (2021). Increasing Trend on Storm Wave Intensity in the Western Mediterranean. Journal of climate, 9(11). https://doi.org/10.3390/cli9010011
  7. Anagnostopoulou, C., Tolika, K., Flocas, H., & Maheras, P. (2006). Cyclones in the Mediterranean region: present and future climate scenarios derived from a general circulation model (HadAM3P). Advances in Geosciences,7: 9-14.
  8. Asakareh, H. (2021). Fundamentals of statistical climatology. Second Edition, Zanjan University Publications. [In Persion].
  9. Asakareh, H., Qaemi, H., Rezaei, SH. (2016). Review mechanism of expansion and low-pressure Red Sea. Geographical Planning of Space, 6(21), 77-90. [In Persion].
  10. Asakereh, H., & Khani Temeliyeh, S. (2022). Analyzing the amount and frequency of daily precipitation in west and southwest Iran during the statistical period of 1979- 2016 affected by the Red Sea low pressure. Quarterly of Geographical Data (SEPEHR), 31(122), 151-166.  https://doi.org/10.22131/sepehr.2022.254787 [In Persion].
  11. Asakereh, H., & Mazini, F. (2010 a). Analysis of the probability distribution for the annual precipitation in the Golestan province. Iran-Water Resources Research, 6 (1), 51-55. [In Persion].
  12. Asakereh, H., & Tarkarani, F. (2020). Some descriptive features and long - term changes of dry season over Iran. Geography and Development, 18(58), 113-132. doi: 10.22111/gdij.2020.5324. [In Persion].
  13. Asakereh, H., Masoodian, A., Tarkarani, F., & Zand karimi, S. (2023). Decadal variations of the onset, cessation, and length of the widespread rainy season in Iran. Theoretical and Applied Climatology, 152, 599-615. https://doi.org/10.1007/s00704-023-04378.
  14. Asakereh, H., Masoodian, S. A., & Tarkarani, F. (2021 a). Long term trend detection of annual precipitation over Iran in relation with changes in frequency of daily extremes precipitation. Journal of Geography and Environmental Hazards 9 (4), 123-143. doi:10.22067/GEOEH.2021.67028.0 [In Persion].
  15. Asakereh, H., Masoodian, S. A., & Tarkarani, F. (2021 b). Variation in the Spatial Factors Affecting Precipitation in Relation to the Decadal Changes of Annual Precipitation in Iran. Geography and Environmental Planning, 32(3), 129-146. doi: 10.22108/gep.2021.127032.1395. [In Persion].
  16. Asakereh, H., Mazini, F. (2010 b) Investigation of dry days occurrence probability in golestan province using Markove Chain Model. Geography and Development, 8 (17), 29-44. Doi: 10.22111/GDIJ.2010.1132. [In Persion].
  17. Azadi, M., Rezazadeh, P., Mirzaei, E., & Gholamali, V. (2012). Numerical prediction of winter systems over Iran: a comparative study of physical parameterizations. 8th Conference on Fluid Dynamics, Tabriz University. [In Persion].
  18. Carnell, R. E., & Senior C. A. (1998). Changes in mid-latitude variability due to increasing
  19. Darand, M. (2014). Detection of Geopotential Height Changes, Vorticity and Sea Level Pressure of Prevailing Circulation Atmospheric Patterns Impacting Iran Climate. Physical Geography Research Quarterly, 46(3), 349-374. doi: 10.22059/jphgr.2014.52136. [In Persion].
  20. Dayan, U., & Abramsky, R. (1983). Heavy rain in the middle east related to unusual jet stream properties. Bull. Amer. Meteor, 64 (10), 1138-1140.
  21. Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., & Vitart, F. (2011). The ERA‐Interim reanalysis: Configuration and performance of the data assimilation system. Quarterly Journal of the royal meteorological society, 137(656), 553-597.
  22.  Earth's Future, 8(7). doi:10.1029/2020EF001502.
  23. Gaertner, M. A., Jacob, D., Gil, V., Domínguez, M., Padorno, E., Sánchez, E., & Castro, M. (2007). Tropical cyclones over the Mediterranean Sea in climate change simulations. Geophysical Research Letters, 34(14).
  24. Giorgi, F. (2006) Climate change hot-spots. Geophys Res Lett, 33(8). doi:10.1029/2006GL025734.
  25. Giuseppe Zappa, K., Hawcroft, M., Len, Sh., Emily, B., & David, B. (2014). Extratropical cyclones and the projected decline of winter Mediterranean precipitation in the CMIP5 models. Clim Dyn, 1727–1738.
  26.  greenhouse gases and sulphate aerosols, Climate Dynamics,14, 369-383.
  27. Haile, G.G., Tang, Q., Moghari, S.M.H., Liu, X., Gebremicael, T.G., Leng, G., Kebeda, S., Xu, X., & Yun, X. (2020). Projected impacts of climate change on drought patterns over East Africa.
  28. Hamidianpoor, M., Alijani, B., & Sadeghi, A.R. (2022). Identification of synoptic patterns of extreme precipitation in northeastern Iran. Geographical Studies of Arid Regions, 1(1), 1-16. [In Persion].
  29. Hejazizade, Z., & Sedaghat, M. (2010). Numerical Tracking of Middle Eastern Cyclones in the Cold Period of the Year. Physical Geography Research Quarterly, 41(69). [In Persion].
  30. Irannejad, P., Ahmadi-Givi, F., & Mohammadnejad, A. (2016). Effect of Mediterranean cyclogenesis centers on annual precipitation of Iran during 1960 to 2002. Iranian Journal of Geophysics3(1), 91-105. [In Persion].
  31. Kerlinger, F. Elazarji. P. (2016). Multivariate Regression In Behavioral Research. Hasan Saraei, Samt Publications. [In Persion].
  32. Khosh Akhlaq, F. (2016). The Study Of Widespread Iranian Drought Using Synoptic Analysis. doctoral thesis, Tabriz University. [In Persion].
  33. Khoshakhlagh, F., Ahmadi, N., & Karimi, M. (2019). Synoptic Analysis of the Effect of Global Warming on Atmospheric Levels Temperature Trends in Iran, Quarterly of Geographical Data (SEPEHR), 28(109), 211-222. doi: 10.22131/sepehr.2019.35648. [In Persion].
  34. Khoshnafs, Kh. (2007). The effect of Atlas fluctuations on rainfall in western Iran. Master's thesis, Tabriz University. [In Persion].
  35. Krichak, S.O., Alpert, P., & Krishnamuriti, T.N. (1997). Red Sea Trough/Cyclone Development- Numerical Investigation. Meteorology and Atmospheric Physics, 63, 159-169.
  36. Lashgari, H. (1999). the formation mechanism of the Red Sea convergence zone. Geographical Research Quarterly, 59-58, 167-184. [In Persion].
  37. Lashgari, H. (2008). Routing of the Sudanese low pressure system entering Iran. Modares Journal of Humanities, 2,133-156. [In Persion].
  38. Lashkari, H. (2002). Tracking Sudanean Low Systems Entering Iran. The Journal of Spatial Planning, 6 (2),133-157. [In Persion].
  39. Lashkari, H. (2003). Mechanism of formation, strengthening and development of low pressure center in Sudan and its role on rainfall in South and Southwest of Iran. Geographical Research Quarterly, 35(3). [In Persion].
  40. Lionello, P., Joans, B., Buzzi, A., Paul, D.- M. (2006). Cyclones in the Mediterranean regin: Climatology and effects on the environment, Cyclones in the Mediterranean regin: Climatology and effects on the environment. 4: 352-372. DOI: 10.1016/S1571-9197(06)80009-1
  41. Masoodian, S. A. (2012). A Synoptic Analysis of Cyclonic Activity During 1961-2003. Journal of Natural Environmental Hazards, 1(1), 15-33. [In Persion].
  42. Miró, J.J., Estrela, M.J., Olcina-Cantos, J., & Martin-Vide, J. (2021). Future Projection of Precipitation Changes in the Júcar and Segura River Basins (Iberian Peninsula) by CMIP5 GCMs Local Downscaling. Journal of Atmosphere, 12: 879. https:// doi.org/10.3390/atmos12070879.
  43. Mofidi, A. & Azar, Z. (2004). synoptical investigation of the impact of Sudanese low-pressure systems on the occurrence of torrential rains in Iran. Geographical Research Quarterly, 77. [In Persion].
  44. Mofidi, A. & Azar, Z. (2013). synoptic climatology of torrential rains originating from the Red Sea region in the Middle East. Geographical Research Quarterly, 19(4), 71-93. [In Persion].
  45. Mohammadi, R., saligheh, M., Naserzadeh, M. H., & Akbari, M. (2020). Synoptic and dynamical analysis of the cyclonic occurrence of heavy rains during the cold period of western Iran. Journal of Meteorology and Atmospheric Science, 3(3), 224-241. [In Persion].
  46. Mostafaii H, Alijani B, Saligheh M. (2016). Synoptic Analysis of Widespread Heavy Rains in Iran. Journal of Spatial Analysis Environmental Hazards, 2 (4), 65-76. [In Persion].
  47. Nouri, H. & Ildarmi, A. (2013). analysis of synoptic conditions and dynamics of heavy rainfall events on the southern shores of the Caspian in comparison with Iran-Zamin. Journal of Geography and Planning, 16(41), 197-236. [In Persion].
  48. Poorkarim, R., Asakereh, H., faraji, A., & Khosravi, M. (2023). Trends analysis of changes in the number of the Mediterranean cyclones (1979-2018). Journal of Spatial Analysis Environmental Hazards, 9 (4):211-222. [In Persion].
  49. Radinovic, D. (1987). Mediterranean cyclones and their influence on the weather and climate, WMO, PSMP Rep. Ser. Num 24.
  50. Rasouli, A., Babaian, I., Qaemi, H., & Zovar Reza, P. (2013). Analysis of time series pressure centers of synoptic patterns effecting on seasonal rainfall in Iran. Geography and Development, 10(27), 77-88. [In Persion].
  51. Raziei, T., & Sotoudeh, F. (2017). Investigation of the accuracy of the European Center for Medium Range Weather Forecast (ECMWF) in forecasting observed precipitation in different climates of Iran. Journal of the Earth and Space Physics, 43(1), 133-147. doi: 10.22059/jesphys.2017.57958. [In Persion].
  52. Reiter, E. R. (1975). Handbook for Forecasters in the Mediterranean. Nav. Postgrad. Sch., Monterey, Ca.5-75, 344.
  53. Sabzi-Parvar, A.A. (2008). floods formation in the synoptic systems of southwestern Iran. Master's thesis, University of Tehran. [In Persion].
  54. Skliris, N., Sofianos, S., Gkanasos, A., Mantziafou, A., Vervatis, V., Axaopoulos, P., & Lascaratos, A. (2012). Decadal Scale Variability of Sea Surface Temperature in the Mediterranean Sea in Relation to Atmospheric Variability. Ocean Dynam, 62(1), 13–30.
  55. Steven, J., John, L., Fyfe, C. (2006). Changes in winter cyclone frequencies and strengths simulated in enhanced greenhouse warming experiments: results from the models participating in the IPCC diagnostic exercise. Climate Dynamics, 26, 713-728. DOI 10.1007/s00382-006-0110-3.
  56. Swiss, Re. (2020). Catástrofes Naturales en Tiempos de Acumulación Económica y Riesgos Climáticos. Informes Sigma Available online: https://www.swissre.com/institute/research/sigma-research/sigma-2020-02.html.
  57. Tolika, K., Anagnostopoulou, C., Flocas, H., & Maheras, P. (2006). Cyclones in the Mediterranean region: present and future climate scenarios derived from a general circulation model (HadAM3P). Advances in Geosciences, 7, 9-14.
  58. Trigo, I. F. & T. D. Davies. (1999). Objective climatology of cyclones in the Mediterranean region. J Climate, 12,1685–1696. doi:10.1175/1520-0442(1999)012,1685: OCOCIT.2.0.CO;2.
  59. Vahidi Assal, M. (1997). Statistics and probability in geography. (2), Payam Noor University Publications. [In Persion].
  60. Walsh, K. (2004). Tropical cyclones and climate change. Unresolved issues, Clim. Res. 27: 77–83.
  61. Xoplaki, E., González-Rouco, J. F., Luterbacher, J., and Wanner, H. (2004) Wet season Mediterranean precipitation variability: influence of large-scale dynamics and predictability. Clim. Dyn, 23, 63-78.
  62. Zaari, K. (2010). Predicting temperature and precipitation changes in the Midwest of Iran in relation to the position and pressure of atmospheric action centers. master's Thesis, under the guidance of Dr. Faramarz KHoshakhlaq, University of Tehran. [In Persion].
  63. Zarei, S. (2009). A Synoptic Analysis of Cyclonic Activity over Iran in 2014. Isfahan University, supervisor: Dr. Hojat Elah Yazdan Panah and Dr. Seyed Abolfazl Masoudian. [In Persion].