مدل‌سازی عددی خواص فیزیکی، جریان‌ها و پیچک‌های دریای خزر جنوبی

نوع مقاله : مقاله تحقیقی‌ (پژوهشی‌)

نویسندگان

1 دانش‌آموخته کارشناسی ارشد، موسسه ژئوفیزیک دانشگاه تهران، تهران، ایران

2 دانش آموخته دکتری، مرکز علوم جوی و اقیانوسی سازمان هواشناسی، تهران، ایران

چکیده

پژوهش حاضر به مطالعه تغییرات فصلی فرایندهای فیزیکی خزر جنوبی با استفاده از مدل اقیانوسی ROMS می‌پردازد. این مدل عددی برای هفت سال اجرا شد و خروجی‌های آن در سال آخر (2018) برای این پژوهش به‌کاررفت. در این شبیه‌سازی از داده‌های سه‌ساعته ECMWF (ERA Interim) برای واداشت‌های جوّی استفاده شده است. با توجه به قرار گرفتن دو رودخانه مهم کورا و سپیدرود در منطقه مورد مطالعه، ورودی این دو رود به مدل اِعمال شده است. نتایج مدل با داده‌های مشاهداتی و مدل‌سازی قبلی در دریای خزر اعتبارسنجی شده‌اند. بررسی‌ها نشان داد این مدل با مشاهدات میدانی و مدل‌های عددی اجراشده درگذشته همخوانی خوبی دارد. نتایج نشان می‌دهد تغییرات فصلی دما نسبت به شوری در این حوزه چشمگیرتر است. متوسط دمایی که مدل برای این حوزه برآورد کرده است، حدود 16 تا 18 درجه سانتی‌گراد است و مقدار میانگین برای شوری حدود 5/13 واحد شوری است. در بیشتر فصول، الگوهای جریان در این حوزه به‌صورت پادساعت‌گرد هستند. این الگوها که ناشی از وجود بادهای غالبی هستند که به‌صورت شمالی- جنوبی به سمت سواحل ایران می‌وزند، به شکل سواحل خزر جنوبی نیز وابسته‌اند. این جریانات سطحی که به‌ دلیل باد شکل می‌گیرند، با توپوگرافی خزر جنوبی کنترل می‌شوند و در بیشتر فصول، پیچک‌هایی را تشکیل می‌دهند که برخی از آنها دوقطبی هستند. مهم‌ترین نتیجه این تحقیق می‌تواند نوسانات حدود 5 تا 10 سانتی‌متری تراز سطحی خزر به دلیل وجود این پیچک‌ها باشد که بسته به چرخندی و واچرخندی بودن، می‌توانند تراز آب را افزایش یا کاهش دهند. بر اساس نتایج، هنگامی که پیچک‌ها چرخندی هستند، مرکز آب سرد تشکیل می‌دهند. این توده آب حدود نیم تا یک درجه سردتر از آب اطراف خود است. در پیچک‌های واچرخندی که مرکز گرم دارند، تراز آب‌های سطحی بیشتر از آب‌های اطراف است؛ ازاین‌رو این پیچک‌ها دو اثر مهم بر جای می‌گذارند که شامل تغییرات توزیع دمای سطحی و نوسانات سطح خزر است. البته نقش این پیچک‌ها را در پخش آلودگی‌های نفتی نمی‌توان نادیده گرفت.
 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical modeling of physical properties, currents and eddies in the Southern Caspian Sea

نویسندگان [English]

  • Javad Babagoli 1
  • Behzad Layeghi 2
1 M.Sc. Gradute, Oceanic and Atmospheric Science Centre (OASC), Tehran, Iran
2 Ph.D. Gradute, Oceanic and Atmospheric Science Centre (OASC), Tehran, Ira
چکیده [English]

The Caspian Sea is the greatest lake in the world. This basin plays a significant role in the climate of the countries located in the vicinity of it. This water body is divided into three basins, including the northern, middle, and southern parts. The Iranian coasts are located in the southern part. This paper uses the ROMS model to investigate the seasonal changes in physical oceanography phenomena in the Southern Caspian Sea. To deal with this, the model was run for seven years. The GEBCO data are utilized to make the grid file with the resolution of 30 seconds. Three-hourly ECMWF (ERA Interim) data was applied to the model. Furthermore, the Kura and the Sepidrud rivers were considered for simulation. The climatology and initial conditions data were extracted from World Ocean Atlas 2013 and ICOADS, respectively. In this research, the horizontal resolution of 2.5 km and 16 layers in vertical grids were applied to the model. The model outputs are validated with observation data and other simulations in this basin. The results show that the ROMS can be an appropriate model for simulation in this region, particularly in the southern part, as the outputs are compatible with the observation data. Moreover, the results indicate that the seasonal changes of temperature are remarkable compared to salinity.
    While the model has recorded the mean value of 16°-18° C for temperature, this value for salinity is 13.5 PSU. The typical surface currents are counter-clockwise as the dominant winds are from the north to the south towards the Iranian coasts. The topography of the southern part controls these currents because most eddies are formed in the vicinity of the deep part of the south part. Some eddies are dipoles that can be observable in most seasons. The strongest eddies are formed in this basin in the fall, particularly in December. The most important finding of this research can be the fluctuation of the surface water, which varies from 5 to 10 cm, due to these cyclonic and anticyclonic eddies. When eddies are cyclonic, they form the center of cold water. This water mass can be 0.5°-1° C colder than the surrounded water. Herein, we conclude that these eddies can have two considerable effects on sea surface temperature distributions and sea surface height. Thus, this model shows the behaviors of eddies correctly. It should be noted that eddies can play a significant role in the propagation of oil spills in the southern parts, which is discussed in this paper.
 

کلیدواژه‌ها [English]

  • Southern Caspian Sea
  • Numerical modeling
  • Currents and Eddies
  • Warm and Cold core
  • Changes in Sea Surface height
Arakawa, A., and Suarez, M. J., 1983, Vertical differencing of the primitive equations in sigma coordinates: Monthly Weather Review, 111, 34–45.
Aubrey, D. G., 1994, Conservation of biological diversity of the Caspian Sea and its coastal zone: A proposal to the Global Environment Facility, Report to GEF.
Aubrey, D. G., Glushko T. A., and Ivanov, V. A., 1994, North Caspian Basin: Environmental status and oil and gas operational issue: Report for Mobil-oil.
Babagoli, J., Aliakbari Bidokhti, A., and Salmani Ghazvini, Z., 2018, Investigation of physical properties and long coastal waves in the Southern Caspian Sea: Iranian Journal of Geophysics, 12(3), 39-52.
Babagoli Matikolaei, J., and Aliakbari Bidokhti, A. A., 2019, An experimental study of flow regimes of a gravity current over a cape in a stratified environment: Ocean Dynamics,
 
69(7), 769-786.
Babagoli Matikolaei, J., Aliakbari Bidokhti, A., and Shiea, M., 2019, Some aspects of the deep abyssal overflow between the middle and southern basins of the Caspian Sea: Ocean Science, 15(2), 459-476.
Babagoli Matikolaei, J., 2021, Impact of physical process on propagating oil spills in the Caspian Sea: Marine Pollution Bulletin, 165, 112-147.
Bahmanzadegan, A. R., Lari, K., Fatemi, M. R., and Azarsina, F., 2013, The pattern determination of sea surface temperature distribution and chlorophyll a in the Southern Caspian Sea using SOM Model: Iranian Journal of Fisheries Sciences, 12(1), 105-114.
Bondarenko, A. L., 1993, Currents of the Caspian Sea and formation of salinity of the waters of the north part of the Caspian Sea, Nauka, Moscow, 6, 3019–3053.
Brearley, J. A., Sheen, K. L., Naveira Garabato, A. C., Smeed, D. A., and Waterman, S., 2013, Eddy-induced modulation of turbulent dissipation over rough topography in the Southern Ocean: Journal of Physical Oceanography, 43(11), 2288-2308.
Busireddy, N. K. R., Ankur, K., and Osuri, K. K., 2019, Significance of mesoscale warm core eddy on marine and coastal environment of the Bay of Bengal, in Coastal and Marine Environments - Physical Processes and Numerical Modelling, DOI:10.5772/intechopen.86243.
Cardona, Y., and Bracco, A., 2012, Enhanced vertical mixing within mesoscale eddies due to high frequency winds in the South China Sea: Ocean Modelling, 42, 1-15.
Chelton, D. B., and Xie, S. P., 2010, Coupled ocean-atmosphere interaction at oceanic mesoscales: Oceanography, 23(4), 52-69.
Chen, J. L., Pekker, T., Wilson, C. R., Tapley, B. D., Kostianoy, A. G., Cretaux, J. F., and Safarov, E. S., 2017, Long-term Caspian Sea level change: Geophysical Research Letters, 44(13), 6993-7001.
Ghaffari, P., and Chegini, V., 2010, Acoustic Doppler Current Profiler observations in the Southern Caspian Sea: shelf currents and flow field off Feridoonkenar Bay, Iran: Ocean Science, 6(3), 737-748.
Ghaffari, P., Isachsen, P. E., and LaCasce, J. H., 2013, Topographic effects on current variability in the Caspian Sea: Journal of Geophysical Research: Oceans, 118(12), 7107-7116.
Gunduz, M., and Özsoy, E., 2014, Modelling seasonal circulation and thermohaline structure of the Caspian Sea: Ocean Science, 10(3), 459-471.
Haidvogel, D. B., Arango, H., Budgell, W. P., et al., 2008, Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the Regional Ocean Modeling System: Journal of Computational Physics, 227(7), 3595-3624.
Ismailova, B. B., 2004, Geo-information modeling of wind-induced surges on the northern–eastern Caspian Sea: Mathematics and Computers in Simulation, 67, 371–377.
Kaplin, P., 1995, The Caspian: Its past, present and future, in Mandych, A. F., ed., Enclosed Seas and Large Lakes of Eastern Europe and Middle Asia, SPB, The Hague.
Kara, A. B., Wallcraft, A. J., Metzger, E. J., and Gunduz, M., 2010, Impacts of freshwater on the seasonal variations of surface salinity and circulation in the Caspian Sea: Continental Shelf Research, 30(10-11), 1211-1225.
Kashkooli, O. B., Ghadami, M., Amini, M., and Modarres, R., 2019, Spatiotemporal variation of the Southern Caspian Sea surface temperature during 1982–2016: Journal of Marine Systems, 193, 126-136.
Komijani, F., Chegini, V., Sadrinasab, M., and Siadatmosavi, S. M., 2016, Simulation of 3D current pattern, sea surface temperature and salinity distribution in the south of Caspian Sea: Marine-Engineering, 12(23), 69-80.
Kosarev, A., and Yablonskaya, E., 1994, The Caspian Sea: SPB Academic Publishing, Hague.
Kostianoy, A. G., and Kosarev, A. N., (eds.), 2005, The Caspian Sea environment: Springer Science & Business Media, 5.
Layeghi, B., Aliakbari Bidokhti, A., Ghader, S., and Azadi, M., 2019, Numerical simulations of oceanographic characteristics of the Persian Gulf and Sea of Oman using ROMS model: Indian Journal of Geo Marine Sciences, 48(12), 1978-1989.
Lu, J., and Speer, K., 2010, Topography, jets, and eddy mixing in the Southern Ocean: Journal of Marine Research, 68(3-4), 479-502.
Mammadov, T. S., and Balapour, S., 2015, Climate change impacts on Azerbaijan biodiversity in the Caspian Sea: Procedia Environmental Sciences, 29, 4.
Medvedev, I., Kulikov, E., and Fine, I., 2020, Numerical modelling of the tides in the Caspian Sea: Ocean Science, 16, 209–219, 2020.
Mehdinia, A., Dehbandi, R., Hamzehpour, A., and Rahnama, R., 2020, Identification of microplastics in the sediments of southern coasts of the Caspian Sea, north of Iran: Environmental Pollution, 258, 113738.
Petroody, S. S. A., Hashemi, S. H., and van Gestel, C. A., 2020, Factors affecting microplastic retention and emission by a wastewater treatment plant on the southern coast of Caspian Sea: Chemosphere, 261, 128179.
Rahnemania, A., Aliakbari Bidokhti, A., and Babagoli Matikolaei, J., 2018, Study of ice formation in the Caspian Sea using numerical simulations: Journal of the Persian Gulf, 9(33), 25-34.
Rahnemania, A., Aliakbari Bidokhti, A., and Babagoli Matikolaei, J., 2021, Some physical properties of mesoscale eddies in the Caspian Sea basins based on numerical simulations: Journal of Earth and Space Physics, 47(4), 219-230.
Shchepetkin, A. F., and McWilliams, J. C., 2005, The regional ocean modeling following coordinates ocean model: Ocean Modelling, 9(4), 347-404.
Shiea, M., Chegini, V., and Bidokhti, A. A., 2016, Impact of wind and thermal forcing on the seasonal variation of three-dimensional circulation in the Caspian Sea: Indian Journal of Geo-Marine Sciences, 45(5), 671–686.
Stanley, G. J., and Saenko, O. A., 2014, Bottom-enhanced diapycnal mixing driven by mesoscale eddies: Sensitivity to wind energy supply: Journal of Physical Oceanography, 44(1), 68-85.
Sun, W., Dong, C., Tan, W., and He, Y., 2019, Statistical characteristics of cyclonic warm-core eddies and anticyclonic cold-core eddies in the North Pacific based on remote sensing data: Remote Sensing, 11(2), 208.
Terziev, F. S., Kosarev, A., and Kerimov, A. A., 1992, The Seas of the USSR. Hydrometeorology and Hydrochemistry of the Seas, Vol. IV: The Caspian Sea, Issue 1: Hydrometorogical Conditions, Gidrometeoizdat, St. Petersburg, Russia.
Turuncoglu, U. U., Giuliani, G., Elguindi, N., and Giorgi, F., 2013, Modelling the Caspian Sea and its catchment area using a coupled regional atmosphere-ocean model (RegCM4-ROMS): model design and preliminary results: Geoscientific Model Development, 6(2), 283-299.
Warner, J. C., Sherwood, C. R., Signell, R. P., Harris, C. K., and Arango, H. G., 2008, Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model: Computers & Geosciences, 34(10), 1284-1306.