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تحلیل اختلاف درجۀ حرارت هوا و دریا بر بارش‌های سنگین و فراگیر سواحل جنوبی خزر طی فصل پاییز | ||
| پژوهش های جغرافیای طبیعی | ||
| مقاله 6، دوره 49، شماره 1، فروردین 1396، صفحه 71-83 اصل مقاله (1.53 M) | ||
| نوع مقاله: مقاله کامل | ||
| شناسه دیجیتال (DOI): 10.22059/jphgr.2017.61580 | ||
| نویسندگان | ||
| همت اله رورده* ؛ طاهر صفرراد | ||
| استادیار اقلیم شناسی، دانشکدة علوم انسانی و اجتماعی، دانشگاه مازندران | ||
| چکیده | ||
| در پژوهش پیش رو ارتباط بین اختلاف درجة حرارت سطح دریا و هوا بر بارش‌های سنگین و فراگیر سواحل جنوبی خزر طی فصل پاییز بررسی شده است. دادههای روزانة بارش ایستگاه‌های سینوپتیکِ آستارا، بندر انزلی، رشت، رامسر، بابلسر، قائمشهر، و گرگان طی سالهای 1986 تا 2013 گردآوری شد. روزهایی که مقدار بارش آن‌ها حداقل در پنج ایستگاه بیشتر از صدک 95 آن سال بود به عنوان روزهای بارش سنگین و فراگیر تعریف شد. مشخص شد که افزایش در بخشهای جنوبی خزر بارش‌های سنگین و فراگیر را فقط در بخش شرقی منطقة مورد مطالعه به صورت معناداری افزایش میدهد. با بهرهگیری از روش ادغام وارد و محاسبة همبستگی بین دادهها، سه خوشه تشخیص داده شد: خوشة اول بیشینة شیو در راستای شمال غرب به جنوب شرق؛ خوشة دوم در راستای شمال به جنوب؛ و خوشة سوم در راستای غرب به شرق را بیان میکنند. ایستگاه‌های واقع در شرق منطقة مورد مطالعه در خوشة دوم بارش بیشتری داشتند؛ برعکس، ایستگاههایی که در غرب قرار داشتند طی خوشة سوم بیشترین بارش را دریافت میکردند. بر اساس واکاوی همدیدی خوشهها، استقرار هستة پُرفشار در شمال غرب دریای خزر سببِ ریزش هوای سرد از عرضهای شمالیتر و ایجاد بارش‌های سنگین و فراگیر در منطقه میشود. | ||
| کلیدواژه‌ها | ||
| اختلاف درجة حرارت دریا و هوا؛ بارش سنگین و فراگیر؛ سواحل جنوبی خزر؛ فصل پاییز | ||
| عنوان مقاله [English] | ||
| Analysis of Sea-air Temperature Difference on Regional Heavy Precipitation in the Southern Coasts of Caspian Sea during Fall | ||
| نویسندگان [English] | ||
| Hematollah Roradeh؛ Taher Safarrad | ||
| Assistant Professor of Climatology, Department of Geography and Urban Planning, Faculty of Humanities and Social Science, University of Mazandaran, Babolsar, Iran | ||
| چکیده [English] | ||
| Introduction With the onset of fall season, the air temperature on the Caspian Sea is diminished, but due to the difference in the specific heat capacity of air and water, the reduction rate of temperature is far greater than that of the sea. Therefore, the surface of Caspian Sea remains warmer than air. Establishment of dynamic high-pressure centers or diffusion of Siberian high pressure system over Caspian Sea especially during fall results in development of southward air stream over the sea. Caspian Sea as the first supplier of moisture resources for heavy precipitation and especially ultra-heavy precipitation of its southern coasts plays a principal role in explanation of the occurrence of precipitations in these coasts. The changes in Caspian Sea water temperature can result in variations in the precipitation in southern coasts of Caspian Sea. However, the seawater temperature is not sufficient for the precipitations of the southern coasts of Caspian Sea and the air temperature over the sea should also be taken into consideration. The sea-air temperature difference (ΔT), as humidity intake index, has attracted the attention of researchers to such an extent that it has become the most important thermodynamic factor in development of abundant and heavy precipitations in the southern coasts of Caspian Sea. Gradual increase of the sea surface temperature in its proper arrangement from the north to the south and intake of humidity from the sea (ΔT index) have been considered necessary for development of heavy and ultra-heavy precipitations in the southern coasts of Caspian Sea. Materials and methods In this research, the daily precipitation data of seven synoptic stations of Northern provinces of Iran have been collected from 1968 to 2013. The threshold of heavy precipitations was defined as the day in which its precipitation level is greater than the percentile 95 of that year. Then, all of the days in which at least five stations have recorded heavy precipitation were simultaneously extracted and considered as regional heavy precipitation days. By extracting the air temperature at 2 meter above the sea level (Air2m) and the sea surface temperature (SST), the ΔT value was calculated as follows: Using Ward linkage method and correlation between the data, ΔT values were clustered in the days in which regional heavy precipitation had occurred in the northern stations of Iran. In each of the clusters, the day that had the greatest correlation with other days was selected as the sample. For the sample days, SLP, VWnd, Uwnd, and HGT data in 1000 HPa for analysis of synoptic conditions leading to regional heavy precipitation were extracted from http://www.esrl.noaa.gov. The relationship between regional heavy precipitation in the stations and ΔT was analyzed to interpret the extracted clusters. Results and discussion With the onset of fall season, the air temperature experiences more rapid decline than seawater temperature. Therefore, in this season, the sea will be warmer than air. The long-term mean (1986-2013) of SST and Air2m and ΔT during fall has been shown in Fig. 1. Fig.1: Long-term mean (1986-2013) of SST and Air2m and ΔT during fall. The relationship between regional heavy precipitation and ΔT was investigated in the studied stations. Unexpectedly, direct relationship between ΔT in the south Caspian Sea and regional heavy precipitation does not exist in all of the stations. This relationship only applies to the stations located in the East, whereas in the stations situated in the West, this was inverse relation. Using Ward linkage method and calculation of the correlation between the data, three clusters were recognized. In each of the clusters, the day that had the greatest correlation with other days was selected as the representative of the cluster (Fig. 2). The first cluster is representative of the days with regional heavy precipitation in conditions where ΔT gradient reaches its maximum from Northwest to the southeast. The second cluster represents incidence of regional heavy precipitation in conditions where the maximum ΔT gradient is from the north to the south. Eventually, the third cluster can be considered as the greatest ΔT gradient observed from the West to the East (also Southwest to Northeast). Fig.2: ΔT in 13 Sep 1977 (lesf cluster), 22 Oct 1988 (middle cluster) and 29 Sep 1986 (right cluster) Investigation of synopsis maps of regional heavy precipitation in the selected days suggests their similar synoptic conditions such that establishment of high-pressure center in the northwest Caspian Sea leads to influx of cold-air from more northern latitudes and over Caspian Sea towards southern latitudes. The stations located in the east part of the study area will receive greater precipitation when ΔT reaches its maximum level in the southern coasts of Caspian Sea (the second cluster). In contrast, the stations located in the West will receive greater precipitation when ΔT gradient increases from the east to the west (the third cluster). Conclusion With the increase in ΔT in the southern parts of Caspian Sea, regional heavy precipitation grows significantly only in the eastern part of the study area. The results obtained from ΔT clustering unveiled three clusters, where the first, second, and third clusters represented the maximum ΔT gradient from the Northwest to the southeast, north to the south, and west to the east, respectively. The stations located in the east part of the studied region will have greater precipitation when ΔT reaches its maximum in the southern coasts of Caspian Sea (the second cluster). In contrast, the stations located in the West will receive the maximum precipitation when ΔT gradient increases from the east to the west (the third cluster). These results were in line with those obtained from investigation of the correlation between ΔT and regional heavy precipitation. The analysis of synoptic maps indicated that in all of the three clusters, establishment of high-pressure center in the northwest part of Caspian Sea results in infusion of cold air from more northern latitudes over Caspian Sea and towards southern latitudes. | ||
| کلیدواژه‌ها [English] | ||
| autumn, regional heavy precipitation, sea-air temperature difference, southern coasts of Caspian Sea | ||
| مراجع | ||
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براتی، غ. و عاشوری، ف. (1386). طراحی الگوهای همدید شدیدترین بادهای کرانههای جنوبی دریای خزر، پژوهشهای جغرافیایی، 62: 67-80. رضیئی، ط؛ مفیدی، ع. و زرین، آ. (1387). مراکز فعالیت و الگوهای گردش جو زمستانة تراز 500 هکتوپاسکال روی خاورمیانه و ارتباط آن‌ها با بارش ایران، مجلة فیزیک زمین و فضا، 35(1): 121-141. عسگری، ا.؛ رحیم‌زاده، ف.؛ محمدیان، ن. و فتاحی، ا. (1386). تحلیل روند نمایه‌های بارش‌های حدی در ایران، تحقیقات منابع آب ایران، 3(9): 42-55. علیجانی، ب. (1372). مکانیزمهای صعود بارندگی‌های ایران، مجلة دانشکدة ادبیات دانشگاه تربیت معلم، 1: 85-101. علیجانی، ب.؛ محمدی، ح. و بیگدلی، آ. (1386). نقش الگوهای فشار در بارش‌های سواحل جنوبی دریای خزر، فصلنامة جغرافیایی سرزمین، 4(16): 37-51. محمدی، ع.؛ عابدینی، م. و عسگری شیرازی، ح. (1391). تحلیل همدیدی اثر دمای سطح آب دریای خزر بر بارش استان مازندران، فصلنامة علوم و فنون دریایی، 61(61): 40-52. مرادی، ح. (1372). نقش دریای خزر در شرایط بارشی سواحل شمالی کشور، مجلة علوم و فنون دریایی ایران، 2(2-3): 77-88. مفیدی، ع.؛ زرین، آ. و جانبازقبادی، غ. (1386). تعیین الگوی همدیدی بارش‌های شدید و حدی پاییزه در سواحل جنوبی دریای خزر، مجلة فیزیک زمین و فضا، 33(3): 131-154. مفیدی، ع.؛ زرین، آ. و جانبازقبادی، غ. (1391). تبیین علل کاهش‌یافتن مقدار و شدت بارش‌های زمستانه در قیاس با بارش‌های پاییزه در سواحل جنوبی خزر، مجلة فیزیک زمین و فضا، 38(1): 177-203. نوری، ح.؛ غیور، ح.؛ مسعودیان، ا. و آزادی، م. (1391). بررسی دمایی اثر سازوکار جوی- دریایی خزر در بارش‌های سنگین و فوق سنگین سواحل جنوبی آن، فصلنامة تحقیقات جغرافیایی، 27(107): 201-226. نوری، ح.؛ غیور، ح.؛ مسعودیان، ا.؛ آزادی، م. (1392). تحلیل فراوانی تابع همگرایی شار رطوبت و منابع رطوبتی بارش سواحل جنوبی خزر، مجلة جغرافیا و برنامه‌ریزی محیطی، 24(51): 1-14. Alijani, B. (1993). Synoptic mechanisms of precipitation in Iran, Journal of the Faculty of Letters and Humanities, Teachers’ Training University, 1: 85-101 (In Persian).
Alijani, B.; Mohammadi, H. and Bigdeli, A. (2008). The role of pressure patterns on the precipitation on the southern coast of the Caspian Sea. Quarterly Geographical Journal of Territory (Sarzamin), 16: 37-52 (In Persian).
Asgari, A.; Rahimzadeh, F.; Mohammadian, N. and Fatahi, E. (2000). Trend Analysis of Extreme Precipitation Indices over Iran, Iran-water resources research, 3(9): 42 - 55 (In Persian).
Barati, Gh.R. and Ashouri, F. (2008). Designing Of Synoptic Patterns of Winds In The Southern Coasts Of Caspian Sea (1983-85), Quarterly Geographical Research, 62: 67-80 (In Persian).
Black, E. (2005). The relationship between Indian Ocean sea–surface temperature and East African rainfall, Philosophical Transactions of the Royal Society of London A: Mathematical,Physical and Engineering Sciences, 363(1826): 43-47.
Black, E.; Slingo, J.M. and Sperber, K.R. (2003). An observational study of the relationship between excessively strong short rains in coastal East Africa and Indian Ocean SST, Mon Wea Rev, 131: 74-94.
Chen, J.-M.; Chang, C.-P. and Li., T. (2003). Annual cycle of the South China Sea surface temperature using the NCEP/NCAR reanalysis, J. Meteor. Soc. Japan, 81: 879-884.
Elsner, J.B.; Kossin, J.P. and Jagger, T.H. (2008). The increasing intensity of the strongest tropical cyclones, Nature, 455(7209): 92-95.
Espinoza, J.C.; Marengo, J.A.; Ronchail, J.; Carpio, J.M.; Flores, L.N. and Guyot, J.L. (2014). The extreme 2014 flood in south-western Amazon basin: the role of tropical-subtropical South Atlantic SST gradient, Environmental Research Letters, 9(12): 124007.
Evans, J.P. and Boyer‐Souchet, I. (2012). Local sea surface temperatures add to extreme precipitation in northeast Australia during La Niña, Geophysical Research Letters, 39(10).
Kalnay et al. (1996). The NCEP/NCAR 40-year reanalysis project, Bull. Amer. Meteor. Soc., 77: 437-470.
Marengo, J.A.; Alves, L.M.; Soares, W.R.; Rodriguez, D.A.; Camargo, H.; Riveros, M.P. and Pabló, A.D. (2013). Two contrasting severe seasonal extremes in tropical South America in 2012: flood in Amazonia and drought in northeast Brazil, Journal of climate, 26(22): 9137-9154.
Marengo, J.A.; Tomasella, J.; Soares, W.R.; Alves, L.M. and Nobre, C.A. (2012). Extreme climatic events in the Amazon basin, Theoretical and Applied Climatology, 107(1-2): 73-85.
Mofidi, A.; Zarrin, A. and Janbaz Ghobadi, Gh.R. (2012).The explanation for the decline in amount and intensity of wintertime precipitation compared with the Autumntime precipitation in the southern coast of the Caspian Sea, Journal of the Earth and Space Physics, 38(1): 177-203 (In Persian).
Mofidi, A.; Zarrin, A. and Janbaz Ghobadi, Gh.R. (2007). Recognizing the Synoptic Patterns of Autumntime Heavy Precipitation in the Southern Coast of the Caspian Sea, Journal of the Earth and Space Physics, 33(3): 131-154 (In Persian).
Mohammadi, A.; Abedini, M. and Asgari Shirazi, H. (2012). Synoptice Analysis Impact Sea surface Temperature at Precipitaition in the province Mazandaran, Iranian Journal of Marine Science and Technology, 61(61): 40-52 (In Persian).Moradi, H.R. (1993). Studying the role of Caspian Sea on Precipitation condition in the shores of the north of Iran, Iranian Journal of Marine Science and Technology, 2-3(2): 77-88 (In Persian).Nouri, H.; Ghayour, H.; Masoodian, A. and Azadi, M. (2013). Analysis of Moisture Flux Convergence and moisture sources for precipitation in the southern coasts of Caspian Sea, Geography and Environmental Planning Journal, 51(3): 1-14 (In Persian).
Nouri, H.; Ghayour, H.; Masoodian, A. and Azadi, M. (2013). Investigation on temperature in sea- air interaction of Caspian Sea for heavy and super heavy precipitation in the southern coasts, Quarterly Geographical Research, 4(107): 201-226 (In Persian).Razeie, T.; Mofidi, A. and Zarrin, A. (2008). Winter activity centers and atmospheric circulation patterns in 500 hPa on the Middle East and their relationship with precipitation in Iran. Journal of the Earth and Space Physics, 35(1): 121-141 (In Persian).
Reynolds, R.W.; Smith, T.M.; Liu, C.; Chelton, D.B.; Casey, K.S. and Schlax, M.G. (2007). Daily high-resolution-blended analyses for sea surface temperature, Journal of Climate, 20(22): 5473-5496.
Tam, C.Y. and Chan, J.C. (2010). Influence of South China Sea SST and the ENSO on winter rainfall over South China, Advances in Atmospheric Sciences, 27(4): 832-844. | ||
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