The general circulation of the atmosphere in the North Atlantic and Pacific and its relationship with development and strengthening the Azores and Hawaiian subtropical anticyclones

Document Type : Research Article

Authors

1 Ph.D. Student, Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran, Iran

2 Professor, Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran, Iran

3 Assistant Professor, Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran, Iran

Abstract

Subtropical anticyclones are among the large-scale atmospheric centers of action in the northern hemisphere in the east of the oceans. Clockwise flow and high surface pressure are two prominent features of these systems. These systems have an annual trend and usually achieve maximum flow and surface pressure in the summer, especially in July. Understanding the factors influencing the development and intensification of these anticyclones has been the favorite of many researchers. One of these factors has been the general circulation of the atmosphere. In this study, a climatological study of the general atmospheric circulation, including the Hadley and Walker circulations, has been performed. Their role in the development and strengthening of subtropical anticyclones has been investigated. The research has been done in three parts; 1- Mean Meridian Circulation, 2- meridional circulation in the North Atlantic and Pacific, and 3- Walker circulation in the North Atlantic and Pacific. In this study, the meridional component of wind, vertical velocity (omega), and horizontal wind divergence have been used. Data at 27 pressure levels with a horizontal resolution of 0.25 × 0.25 ° were extracted from the European Center for Medium Weather Forecasting (ECMWF) and the ERA5 version. The monthly mean of the data used was conducted over 40 years, from 1979 to 2018. The Mass Stream Function (MSF) method has been used to quantify the meridional and walker circulation.
The Mean Meridian Circulation showed that the meridional circulation in the equinox months consists of a pair of Hadley cells in which air rises in the tropics and subsides in the subtropics. Also, a solstitial cell is found with the ascent in the outer tropics of the summer hemisphere and subsidence in the outer tropics of the winter hemisphere. Although the Mean Meridional Circulation showed that mass transfer takes place in the summer of the Northern Hemisphere to the Southern Hemisphere and the Hadley circulation could not explain and justify the maximum activity of the subtropical anticyclones, but the meridional circulation at smaller cross-sections in the East Atlantic and Pacific showed that the Hadley cells play a vital role in mass transfer to the subtropics and mid-latitudes. The mean walker circulation (20-40 ° N) showed that the source of this circulation is only the latent heat released over the waters and the lands of the western oceans that have no role in mass transfer to the east. Westerly and southwesterly winds also form mass transfer in the Walker circulation to the northeast of the oceans. Heating in northwestern Africa and North America is another phenomenon that plays a role in subsidence in the North Atlantic and Pacific. The subsidence induced from heating on African lands is much more severe than that in North America. This may depend on the climate and extent of these areas. Therefore, as a result of this research, it can be said that three processes: Hadley circulation, Walker circulation, and heating on the lands adjacent to the eastern oceans, are effective in mass transfer and subsidence in the east Atlantic and Pacific. These conditions form strong northerly winds in the eastern oceans and trade winds in the tropics and effectively develop and strengthen subtropical anticyclones.

Keywords

Main Subjects


حجازی‌زاده، ز.، 1372، بررسی نوسانات فشار زیاد جنب‌حاره در تغییر فصل ایران، رساله دکتری جغرافیای طبیعی، دانشگاه تربیت مدرس.
عساکره، ح.، قائمی، ه. و فتاحیان، م.، 1395، اقلیم‌شناسی مرز پشته پرفشار جنب‌حاره بر روی ایران، م. نشریه پژوهش‌‌‌های اقلیم‌شناسی، 26-25(7)، 21-32.
علی‌پور، ی.، حجازی‌زاده، ز.، اکبری، م. و سلیقه، م.، 1397، بررسی تغییرات پرفشار جنب‌حاره تراز 500 هکتوپاسکال نیوار ایران با رویکرد تغییر اقلیم، م. مخاطرات محیط طبیعی، 18(7)، 1-16.
گرمسیری‌مهوار، ع. ا. و عزیزی، ق.، 1399، تحلیلی بر پُرفشارهای جنب‌حاره آزورز و هاوایی، م. پژوهش‌های جغرافیای طبیعی، 3(52)، 409-428.
لشکری، ح.، متکان، ع. ا.، آزادی، م. و محمدی، ز. 1396، تحلیل همدیدی نقش پرفشار جنب‌حاره‌ای عربستان و رودباد جنب‌حاره‌ای در خشک‌سالی‌های شدید جنوب و جنوب غرب ایران، م. پژوهش‌های دانش زمین، 2(8)، 141-163.
Bayr, T., Dommenget, D., Martin, T. and Power, S. B., 2014, The eastward shift of the Walker circulation in response to global warming and its relationship to ENSO variability. Climate dynamics, 43(9-10), 2747-2763.
Bjerknes, J., 1969, Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev, 97(3), 163-172.
Broccoli, A. J., Dahl, K. A. and Stouffer, R. J., 2006, Response of the ITCZ to Northern Hemisphere cooling. Geophysical Research Letters, 33(1).
Chang, E. K., 1995, The influence of Hadley circulation intensity changes on extratropical climate in an idealized model. Journal of the atmospheric sciences, 52(11), 2006-2024.
Chang, E. K., 1996, Mean meridional circulation driven by eddy forcings of different timescales. Journal of the atmospheric sciences, 53(1), 113-125.
Cook, K. H., 2004, Hadley circulation dynamics. In The Hadley circulation: present, past and future (pp. 61-83). Springer, Dordrecht.
Davis, N. A., Seidel, D. J., Birner, T., Davis, S. M. and Tilmes, S., 2016, Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations. Atmospheric Chemistry and Physics, 16(15), 10083-10095.
Dima, I. M. and Wallace, J. M., 2003, On the seasonality of the Hadley cell. Journal of the atmospheric sciences, 60(12), 1522-1527.
Dima, I. M., 2005, An observational study of the tropical tropospheric circulation (Doctoral dissertation).
Ferrel, W., 1856, Essay on the winds and ocean currents. Nashville J. of Medicine and Surgery, 11, 287-301.
Gong, X., Wang, Q. and Liu, Y., 2015, Interannual variability of the Hadley circulation associated with tropical Pacific SST anomaly. Journal of Ocean University of China, 14(4), 596-603.
Hadley, G., 1735, VI. Concerning the cause of the general trade-winds. Philosophical Transactions of the Royal Society of London, 39(437), 58-62.
Held, I. M. and Hou, A. Y., 1980, Nonlinear axially symmetric circulations in a nearly inviscid atmosphere. Journal of the Atmospheric Sciences, 37(3), 515-533.
Holton, J. R., 1992, An Introduction to Dynamic Meteorology. 3d ed. Academic Press, 511 pp.
Hoskins, B. J., (1996, On the existence and strength of the summer subtropical anticyclones. Bull. Amer. Meteor. Soc., 77, 1287-1292.
Hou, A. Y. and Lindzen, R. S., 1992, The influence of concentrated heating on the Hadley circulation. Journal of the atmospheric sciences, 49(14), 1233-1241.
Hurrell, J. W., 1996, Influence of variations in extratropical wintertime teleconnections on Northern Hemisphere temperature. Geophysical Research Letters, 23(6), 665-668.
Johanson, C. M. and Fu, Q., 2009, Hadley cell widening: Model simulations versus observations. Journal of Climate, 22(10), 2713-2725.
Lindzen, R. S. and Hou, A. V., 1988, Hadley circulations for zonally averaged heating centered off the equator. Journal of the Atmospheric Sciences, 45(17), 2416-2427.
Levine, X. J. and Schneider, T., 2011, Response of the Hadley circulation to climate change in an aquaplanet GCM coupled to a simple representation of ocean heat transport. Journal of the Atmospheric Sciences, 68(4), 769-783.
Lindzen, R. S. and Nigam, S., 1987, On the role of sea surface temperature gradients in forcing low-level winds and convergence in the tropics. Journal of the Atmospheric Sciences, 44(17), 2418-2436.
Lu, J., Chen, G. and Frierson, D. M., 2008, Response of the zonal mean atmospheric circulation to El Niño versus global warming. Journal of Climate, 21(22), 5835-5851.
Ma, S. and Zhou, T., 2016, Robust strengthening and westward shift of the tropical Pacific Walker circulation during 1979–2012: A comparison of 7 sets of reanalysis data and 26 CMIP5 models. Journal of Climate, 29(9), 3097-3118.
Numaguti, A., 1995, Dynamics and energy balance of the Hadley circulation and the tropical precipitation zones. Part II: Sensitivity to meridional SST distribution. Journal of the atmospheric sciences, 52(8), 1128-1141.
Nguyen, H., Evans, A., Lucas, C., Smith, I. and Timbal, B., 2013, The Hadley circulation in reanalyses: Climatology, variability, and change. Journal of Climate, 26(10), 3357-3376.
Oort, A. H. and Peixóto, J. P., 1983, Global angular momentum and energy balance requirements from observations. In Advances in Geophysics (Vol. 25, pp. 355-490). Elsevier.
Oort, A. H. and Yienger, J. J., 1996, Observed interannual variability in the Hadley circulation and its connection to ENSO. Journal of Climate, 9(11), 2751-2767.
Peixoto, J. P. and Oort, A. H., 1992, Physics of climate, 520pp., Am. Inst. of Phys., New York.
Rodwell, M. J. and Hoskins, B. J., 2001, Subtropical anticyclones and summer monsoons. Journal of Climate, 14(15), 3192-3211.
Schneider, E. K., 1977, Axially symmetric steady-state models of the basic state for instability and climate studies. Part II. Nonlinear calculations. Journal of the Atmospheric Sciences, 34(2), 280-296.
Schneider, E. K. and Lindzen, R. S., 1977, Axially symmetric steady-state models of the basic state for instability and climate studies. Part I. Linearized calculations. Journal of the Atmospheric Sciences, 34(2), 263-279.
Stachnik, J. P. and Schumacher, C., 2011, A comparison of the Hadley circulation in modern reanalyses. Journal of Geophysical Research: Atmospheres, 116(D22).
Tanaka, H. L., Ishizaki, N. and Kitoh, A., 2004, Trend and interannual variability of Walker, monsoon and Hadley circulations defined by velocity potential in the upper troposphere. Tellus A: Dynamic Meteorology and Oceanography, 56(3), 250-269.
Wallace, J. M., Rasmusson, E. M., Mitchell, T. P., Kousky, V. E., Sarachik, E. S. and Von Storch, H., 1998, On the structure and evolution of ENSO‐related climate variability in the tropical Pacific: Lessons from TOGA. Journal of Geophysical Research: Oceans, 103(C7), 14241-14259.
Yu, B., Zwiers, F. W., Boer, G. J. and Ting, M. F., 2012, Structure and variances of equatorial zonal circulation in a multimodel ensemble. Climate dynamics, 39(9-10), 2403-2419.