پیوندهای مفید
اخبار و اعلانات
آمار
| تعداد نشریات | 161 |
| تعداد شماره‌ها | 6,532 |
| تعداد مقالات | 70,501 |
| تعداد مشاهده مقاله | 124,097,463 |
| تعداد دریافت فایل اصل مقاله | 97,205,183 |
مطالعه فراوانی و توزیع تاشدگی وردایست و تغییرات فصلی آن در سالهای 2013-2015 با تأکید بر منطقه جنوب‌غرب آسیا | ||
| فیزیک زمین و فضا | ||
| مقاله 9، دوره 44، شماره 3، آبان 1397، صفحه 607-624 اصل مقاله (1.18 M) | ||
| شناسه دیجیتال (DOI): 10.22059/jesphys.2018.234992.1006909 | ||
| نویسندگان | ||
| رضا برهانی1؛ فرهنگ احمدی گیوی* 2؛ سرمد قادر2؛ علیرضا محب‌الحجه3 | ||
| 1دانشجوی دکتری، گروه فیزیک فضا، موسسه ژئوفیزیک دانشگاه تهران، ایران | ||
| 2دانشیار، گروه فیزیک فضا، موسسه ژئوفیزیک دانشگاه تهران، ایران | ||
| 3استاد، گروه فیزیک فضا، موسسه ژئوفیزیک دانشگاه تهران، ایران | ||
| چکیده | ||
| هدف این پژوهش مطالعه فراوانی و توزیع جهانی رخداد تاشدگی وردایست، با تأکید بر منطقه جنوب‌غرب آسیا، و همچنین تغییرات فصلی آن در فاصله سالهای 2013 تا 2015 است. بدینمنظور میدانهای اولیه از قبیل باد، دما و ارتفاع ژئوپتانسیلی از دادههای بازتحلیل Interim) ECMWF (ERA- اخذ و میدانهای ثانویه مانند تاوایی پتانسیلی (PV) و دمای بالقوه (θ) محاسبه شده است. تشخیص تاشدگی وردایست دینامیکی بر اساس الگوریتم توسعهیافته روش اسپرنگر و همکاران (2003) و گری (2003) و با استفاده از نیمرخ قائم در هر یک از نقاط شبکه انجام شده است. توزیع زمانی- مکانی تاشدگیها نشان میدهد که فراوانی تاشدگی در عرضهای جنبحارهای و میانی (بین 20 تا 40 درجه) در هر دو نیمکره شمالی و جنوبی بیشتر است و در نیمکره زمستانه نیز این تاشدگیها از فراوانی بیشتری برخوردارند. منطقه جنوب‌غرب آسیا در تمام طول سال دارای بیهنجاری مثبت فراوانی تاشدگی نسبت به مقدار میانگین نیمکره شمالی است. میزان بیهنجاری یاد شده در این منطقه طی فصل‌های مختلف سال متفاوت است و در فصل تابستان همزمان با شکلگیری واچرخند موسمی بر روی عرضهای جنبحارهای اقیانوس هند، فراوانی تاشدگی وردایست به‌شدت افزایش مییابد. بیشترین بیهنجاری مثبت در ماه ژوئن و در دو کانون، یکی بر روی ایران-افغانستان و دیگری در شرق مدیترانه اتفاق میافتد. مطالعه موردی انجام شده در ژوئن 2015 تشکیل دو هسته جریان جتی قوی در منطقه را نشان میدهد و بررسی نقشههای نیمرخ قائم میدانهای باد افقی، دمای بالقوه و PV مربوط به این ماه نیز وجود دو ناحیه اصلی تاشدگی وردایست واقع در غرب این دو هسته جریان جتی و در زیر آن و همچنین وجود دو ناحیه کژفشاری بارز (طبق توازن باد گرمایی) در محل تشکیل تاشدگیها را به‌خوبی تأیید میکند. | ||
| کلیدواژه‌ها | ||
| تاشدگی وردایست؛ تاوایی پتانسیلی؛ دمای بالقوه؛ جنوب‌غرب آسیا؛ موسمی؛ ناپایداری کژفشار | ||
| عنوان مقاله [English] | ||
| Study of tropopause folding frequency and its seasonal changes during 2013-2015 emphasizing over Southwest Asia | ||
| نویسندگان [English] | ||
| Reza Borhani1؛ Farhang Ahmadi-Givi2؛ Sarmad Ghader2؛ Alireza Mohebalhojeh3 | ||
| 1Ph.D. Student, Department of Space Physics, Institute of Geophysics, University of Tehran, Iran | ||
| 2Associate Professor, Department of Space Physics, Institute of Geophysics, University of Tehran, Iran | ||
| 3Professor, Department of Space Physics, Institute of Geophysics, University of Tehran, Iran | ||
| چکیده [English] | ||
| This research is aimed to study the global distribution of tropopause folding frequency and its seasonal changes, emphasizing the ones over the Southwest Asia, for a 3-year period from Jan. 2013 up to Dec. 2015. For this purpose, the European Centre for Medium-Range Weather Forecasts (ECMWF) (ERA- Interim) reanalysis data set including wind, temperature and geopotential height were used. The horizontal resolution of the initial fields is 1×1 degrees in longitudinal and latitudinal directions prepared operationally every six hours at 60 levels. Applying the initial fields, the secondary fields, such as potential vorticity and potential temperature were calculated. From the 60 vertical levels, about 19 levels extending from 600 to 100 hPa cover the depth of all tropopause folding events studied here. In this research, we define the 2PVU potential vorticity surface as the dynamical tropopause (1PVU corresponds to 10-6 m2s-1Kkg-1). Identification of tropopause folding is based on the algorithm developed by Sprenger et al. (2003) and Gray (2003) and refined by Škerlak et al. (2014) using pseudosoundings in each of the grid points. A 3-D labeling algorithm is used to distinguish between stratospheric and tropospheric air masses and labeling them according the PV values. After labeling, the tropopause folds are identified at every grid points from the vertical profiles of the label field as areas of multiple crossings of dynamical tropopause. The frequency of folds at each grid point over a chosen period is calculated from the number of folding divided by the total 6-hourly instances corresponding to the season, and finally expressed as a percentage. According to this algorithm, tropopause folds are classified into three categories as shallow, medium and deep. The analysis of spatio–temporal distributions of tropopause folds shows that the frequency of folding events over subtropical and mid latitude regions (between 20° to 40° north and south latitudes) is higher than the other latitudes in both the Northern and Southern Hemispheres and their frequency is increased remarkably in the winter season. Tropopause foldings in the Northern Hemisphere winter are seen as a relatively narrow band located in the subtropical latitude that surrounds zonally the whole Hemisphere, while in the summer season, foldings are concentrated in the subtropical region of the Eastern Hemisphere. Also, tropopause foldings occur mainly as shallow type in the subtropical region but as medium or deep ones in higher latitudes. Foldings in high latitudes are attributed to large-scale deformation fields, as noted by Holton and Hakim (2013), that are confirmed with water vapor satellite images, while the ageostrophic frontal circulations affect the tropopause deformation in mid latitudes. The other noticeable point is that the Southwest Asia region has positive anomalous values of tropopause folding frequency annually, relative to the Northern Hemisphere mean. This can be partly due to the Rossby wave breaking as pointed out by Martius et al. (2007) and Gabriel and Peters (2008). These anomalous values of folding frequency change in different seasons and obtain their maximum amounts in the summer time. Two regions with the maximum value of the folding frequency more than 5 times the Northern Hemisphere mean, seen over Iran–Afghanistan and the eastern of the Mediterranean Sea that occurred in June. The increase of folding frequency in the Southwest Asia during the summer season can be related mainly to the formation and existence of the monsoon anticyclone over the subtropical region of the Indian Ocean (Tyrlis et al., 2013) and partly to the baroclinic instability events. Results of the case study relevant to tropopause foldings in June 2015 show the existence of two strong jet streams in the aforementioned regions. Also, in the meridional cross-sections of wind and PV fields two principal areas of tropopause folding are seen in the west and downward of the jet streams locations. As expected, the potential temperature maps indicate the existence of marked baroclinic regions associated with the tropopause foldings. | ||
| کلیدواژه‌ها [English] | ||
| tropopause folding, Potential vorticity, potential temperature, Southwest of Asia, monsoon, baroclinic instability | ||
| مراجع | ||
|
احمدی‌گیوی، ف. و پگاه‌فر، ن.، 1383، بررسی اثر تاشدگی وردایست در سامانه‌های جوّی واقع بر کشور ایران در دوره آذر ماه 1382 از دیدگاه تاوایی پتانسیلی، چهارمین همایش پیش‌بینی عددی وضع هوا، تهران. عالم‌زاده، ش.، 1396، اثر گرمایش زمین بر تغییرپذیری جت آفریقا-آسیا و مسیر توفان مدیترانه، رساله دکتری هواشناسی، مؤسسه ژئوفیزیک دانشگاه تهران. محمدی، ع. و محب‌الحجه، ع. ر.، 1392 ، اثر چینش باد در سطح زمین و وردایست بر ناپایداری کژفشار، م. ژئوفیزیک ایران، 7(2)، 114-127. میررکنی، م.، محب‌الحجه، ع. ر. و احمدی‌گیوی، ف.، 1393، نقش گردشهای پوشن‌سپهر در بی‌هنجاری‌های اقلیمی زمستانهای 1386 و 1388، م. ژئوفیزیک ایران، 7(1)، 104-89. Andrews, D. G., Holton, J. R. and Leovy, C. B., 1987, Middle Atmosphere Dynamics. Academic Press, 489 pp. Antonescu, B., Vaughan, G. and Schultz, D. M., 2013, A five-year radar-based climatology of tropopause folds and deep convection over Wales, United Kingdom. Mon. Wea. Rev., 141, 1693–1707. Barnes, E. A. and Hartmann, D. L., 2012, Detection of Rossby wave breaking and its response to shifts of the midlatitude jet with climate change. J. Geophys. Res., 117, D09117. Bell, G. D. and Bosart, L. F., 1993, A case study diagnosis of the formation of an upper-level cutoff cyclonic circulation over the eastern United States. Mon. Wea. Rev., 121, 1635-1655. Bertin, F., Campistron, B., Caccia, J. L. and Wilson, R., 2001, Mixing processes in a tropopause folding observed by a network of ST radar and lidar. Anna. Geophys., 19, 1-11. Bithell, M., Gray, L. J. and Cox, B. D., 1999, A three dimensional view of the evolution of midlatitude stratospheric intrusions. J. Atmos. Sci., 56, 673-688. Browning, K. A., Thorpe, A., Montani, J., Parsons, A. D., Griffiths, M., Panagi, P. and Dicks, E. M., 2000, Interactions of tropopause depressions with an ex-tropical cyclone and sensitivity of forecasts to analysis errors. Mon. Wea. Rev., 128, 2734-2755. Carlson, T. N., 1991, Mid-Latitude Weather Systems. Academic Press, 525 pp. Cox, B. D., Bithell, M. and Gray, L. J., 1995, A general circulation model study of a troposphere-folding event at middle latitudes. Q. J. R. Meteorol. Soc., 121, 883-910. Danielsen, E. F., 1964, Report on project Springfield. DASA-1517, Defense Atomic Support Agency, Washington, D.C. Danielsen, E. F., 1968, Stratospheric– tropospheric exchange based on radioactivity, ozone and potential vorticity. J. Atmos. Sci., 25, 502– 518. Danielsen, E. F., 1990, In defense of Ertel's potential vorticity and its general applicability as a meteorological tracer. J. Atmos. Sci., 47, 2013–2020. Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Hólm, E. V., Isaksen, L., Kållberg, P., Köhler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J., Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N. and Vitart, F., 2011, The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q. J. R. Meteorol. Soc., 137, (656), 553-597. Elbern, H., Hendricks, J. and Ebel, A., 1998, A climatology of tropopause folds by global analyses. Theor. Appl. Climatol., 59, 181–200. Gabriel, A. and Peters, D., 2008, A diagnostic study of different types of Rossby wave breaking events in the Northern Extratropics. J. Meteorol. Soc., Japan, 86, 613–631. Gray, S. L., 2003, A case study of stratosphere to troposphere transport: The role of convective transport and the sensitivity to model resolution. J. Geophys. Res., 108, 45–90. Griffiths, M., Thorpe, A. J. and Browning, K. A., 2000, Convective destabilization by a tropopause fold diagnosed using potential-vorticity inversion. Q. J. R. Meteorol. Soc., 126, 125–144. Holton, J. R. and Hakim, G. J., 2013, An Introduction to Dynamic Meteorology. 5th edition, Academic Press, 532 pp. Hoskins, B. J., McIntyre, M. E. and Robertson, A. W., 1985, On the use and significance of isentropic potential vorticity maps. Q. J. R. Meteorol. Soc., 111, 877–946. Lackmann, G. M., Keyser, D. and Bosart, L. F., 1997, A characteristic life cycle of upper-tropospheric cyclogenetic precursors during the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA). Mon. Wea. Rev., 125, 2729-2758. Martius, O., Schwierz, C. and Davies, H., 2007, Breaking waves at the tropopause in the wintertime Northern Hemisphere: Climatological analyses of the orientation and the theoretical LC1/2 classification. J. Atmos. Sci., 64, 2576–2592. Manney, G. L., Hegglin, M. I., Daffer, W. H., Schwartz, M. J., Santee, M. L. and Pawson, S., 2014, Climatology of upper tropospheric/lower stratospheric (UTLS) jets and tropopauses in MERRA. J. Climateol., 27, 3248–3271. Postel, G. A. and Hitchman, M., 1999, A climatology of Rossby wave breaking along the subtropical tropopause. J. Atmos. Sci., 56, 359–373. Ravetta, F., Ancellet, G., Kowol-Santen, J., Wilson, R. and Nedeljkovic, D., 1999, Ozone, temperature, and wind field measurement in a tropopause fold: Comparison with a mesoscale model simulation. Mon. Wea. Rev., 127, 2641-2653. Reid, H. J. and Vaughan, G., 2004, Convective mixing in a tropopause fold. Q. J. R. Meteorol. Soc., 130, 1195-1212. Rodwell, M. J. and Hoskins, B. J., 2001, Subtropical anticyclones and summer monsoons. J. Climatol., 14, 3192–3211. Rotunno, R., Skamarock, W. C. and Snyder, C., 1994, An analysis of frontogenesis in numerical simulations of baroclinic waves. J. Atmos. Sci., 51, 3373-3398. Russell, A., Vaughan, G. and Norton, E. G., 2012, Large-scale potential vorticity anomalies and deep convection. Q. J. R. Meteorol. Soc., 138, 1627–1639. Škerlak, B., Sprenger, M. and Wernli, H., 2014, A global climatology of stratosphere–troposphere exchange using the ERA-Interim data set from 1979 to 2011. Atmos. Chem. Phys., 14, 913–937. Sprenger, M., Croci Maspoli, M. and Wernli, H., 2003, Tropopause folds and cross-tropopause exchange: A global investigation based upon ECMWF analyses for the time period March 2000 to February 2001. J. Geophys. Res., 108, (D12), 8518. Thorpe, A. J., 1997, Attribution and its application to mesoscale structure associated with tropopause folds. Q. J. R. Meteorol. Soc., 123, 2377– 2399. Tyrlis, E., Lelieveld, J. and Steil, B., 2013, The summer circulation over the eastern Mediterranean and the Middle East: Influence of the South Asian Monsoon. Clim. Dyn, 40, 1103–1123. Tyrlis, E., Škerlak, B., Sprenger, M., Wernli, H., Zittis, G. and Lelieveld, J., 2014, On the linkage between the Asian summer monsoon and tropopause fold activity over the eastern Mediterranean and the Middle East. J. Geophys. Res., 119, 3202–3221. Uccellini, L. W., Keyser, D., Brill, K. F. and Wash, C. H., 1985, The President’s day cyclone of 18–19 February 1976, Influence of upstream trough amplification and associated tropopause folding on rapid cyclogenesis. Mon. Wea. Rev., 113, 962–988. Vaughan, G., Price, J. D. and Howells, A., 1994, Transport into the troposphere in a tropopause fold. Q. J. R. Meteorol. Soc., 120, 1085-1103. Wandishin, M. S., Nielsen-Gammon, J. W. and Keyser, D., 2000, A potential vorticity diagnostic approach to upper-level frontogenesis within a developing wave. J. Atmos. Sci., 57, 3918-3938. Wang, B. and Fan Z., 1999, Choice of South Asian summer monsoon indices. http://apdrc.soest.hawaii.edu/projects/monsoon/seasonal-monidx.html. Wang, B., Wu, R. and Lau, K.-M., 2001, Interannual variability of Asian summer monsoon: Contrast between the Indian and western North Pacific-East Asian monsoons. http://apdrc.soest.hawaii.edu/projects/monsoon/seasonal-monidx.html. Wernli, H. and Bourqui, M., 2002, A Lagrangian “one-year climatology” of (deep) cross-tropopause exchange in the extratropical Northern Hemisphere. J. Geophys. Res., 107, (D2), 4021. Whitaker, J. S., Uccellini, L. W. and Brill, K. F., 1988, A model based diagnostic study of the rapid development phase of the Presidents' Day cyclone. Mon. Wea. Rev., 116, 2337-2365. Ziv, B., Saaroni, H. and Alpert, P., 2004, The factors governing the summer regime of the eastern Mediterranean. Int. J. Climatol., 24, 1859–1871. | ||
|
آمار تعداد مشاهده مقاله: 1,127 تعداد دریافت فایل اصل مقاله: 668 |
||