رياح موسمية

(تم التحويل من الرياح الموسمية)
هذا المقال هو عن عن الموسميات. إذا كنت تريد الاستخدامات الأخرى، انظر رياح موسمية (توضيح).
Advancing monsoon clouds and showers in Aralvaimozhy, near Nagercoil, India
Monsoon clouds arriving at Port Blair, Andaman, India
جزء من سلسلة الطبيعة عن
الطقس
Global tropical cyclone tracks-edit2.jpg
الفصول
المواسم المدارية
العواصف
التساقط
موضوعات
المعاجم
Cumulus clouds in fair weather.jpeg Weather portal

الرياح الموسمية أو رياح المنسون أو الموسميات Monsoon، هي رياح قوية برية أو بحرية، تهب على أطراف القارات وتنشأ بسبب الاختلاف في درجة الحرارة ين اليابس والماء.[1]

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أصل الكلمة

سحب الموسميات على لكنو، أتر پرادش.

مصطلح الموسميات monsoons المستخدم في اللغة الإنگليزية وmousson المستخدم في اللغة الفرنسية مستمد من الكلمة العربية موسم mausim، ويدل تعبير رياح موسمية بمعناه العام على أي نوع من الرياح تهب فوق أي منطقة من سطح الأرض في مواسم معينة من مواسم السنة، أما تعبير رياح موسمية monsoons بمعناه الخاص؛ فإنه يدل على الرياح التي تهب في اتجاه محدد في النصف الأول من العام وتهب في اتجاه مضاد للاتجاه السابق في النصف الثاني من العام، ودورياً.[2] Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains.[3][4]

The major monsoon systems of the world consist of the West African, Asia–Australian, the North American, and South American monsoons.

The term was first used in English in British India and neighboring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area.[5][6]



الخصائص المميزة

منظر لسحب الموسميات على المحيط الهندي فعلى هاورا بريدج، كالكوتا.

تتميز الرياح الموسمية بأنها تغير اتجاهها ما بين الصيف والشتاء، وينحصر نطاق هبوبها فيما بين المدارين، وتنشأ نتيجة لوجود مساحات من اليابس شاسعة الامتداد تجاورها بحار أو محيطات، وبسبب اختلاف الحرارة النوعية لكل من اليابس والماء، فإن مناطق الضغط المرتفع تتكون على المياه في فصل الصيف، في حين تتكون مناطق الضغط المنخفض على اليابس، فتندفع الرياح من الماء إلى اليابس مسببة أمطاراً موسمية غزيرة. أمّا في فصل الشتاء فيحدث عكس هذه الحالة في نظام هبوب الرياح، إذ يتكون نطاق من الضغط المرتفع الفصلي على اليابس، تخرج منه الرياح الموسمية الجافة متجهة إلى المسطحات المائية المجاورة التي تتمركز فوقها مناطق من الضغط المنخفض، وهكذا تتعرض كل من المسطحات المائية واليابس المجاور لنظام فصلي للرياح، تهب في اتجاهات مضادة من فصل إلى آخر.

ويعدّ المحيط الهندي أهم المناطق التي تهب منه الرياح الموسمية وإليه، لذا تعدّ قارة آسيا أكثر قارات العالم تعرضاً للرياح الموسمية، خاصة على سواحلها الجنوبية والشرقية، وذلك لعظم اتساعها ولكثرة تداخلات الماء في يابسها عند أطرافها الجنوبية والشرقية،كما تهب الموسميات على شمالي أستراليا وعلى أطراف خليج غينيا، ويوجد نظام موسمي في جنوب شرقي الولايات المتحدة الأمريكية وهضبة الحبشة واليمن وعسير.

Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains.[7][8]

The major monsoon systems of the world consist of the West African, Asia–Australian, the North American, and South American monsoons.

The term was first used in English in British India and neighboring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area.[9][10]

Strength of impact

On May 28, in the dry season
On August 28, in the rainy season
Western Ghats in 2010
This visualization shows the Asian monsoon and how it develops using observational and modeled data. It also shows some of the impacts.

The impact of monsoon on the local weather is different from place to place. In some places there is just a likelihood of having a little more or less rain. In other places, quasi semi-deserts are turned into vivid green grasslands where all sorts of plants and crops can flourish.

The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands. See photos only taken three months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, as it is essential to use all the rain that is available for growing crops.

Process

Monsoons were once considered as a large-scale sea breeze[11] caused by higher temperature over land than in the ocean. This is no longer considered as the cause and the monsoon is now considered a planetary-scale phenomenon involving the annual migration of the Intertropical Convergence Zone between its northern and southern limits. The limits of the ITCZ vary according to the land–sea heating contrast and it is thought that the northern extent of the monsoon in South Asia is influenced by the high Tibetan Plateau.[12][13] These temperature imbalances happen because oceans and land absorb heat in different ways. Over oceans, the air temperature remains relatively stable for two reasons: water has a relatively high heat capacity (3.9 to 4.2 J g−1 K−1),[14] and because both conduction and convection will equilibrate a hot or cold surface with deeper water (up to 50 metres). In contrast, dirt, sand, and rocks have lower heat capacities (0.19 to 0.35 J g−1 K−1),[15] and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at a more even temperature, while land temperature are more variable.

During warmer months sunlight heats the surfaces of both land and oceans, but land temperatures rise more quickly. As the land's surface becomes warmer, the air above it expands and an area of low pressure develops. Meanwhile, the ocean remains at a lower temperature than the land, and the air above it retains a higher pressure. This difference in pressure causes sea breezes to blow from the ocean to the land, bringing moist air inland. This moist air rises to a higher altitude over land and then it flows back toward the ocean (thus completing the cycle). However, when the air rises, and while it is still over the land, the air cools. This decreases the air's ability to hold water, and this causes precipitation over the land. This is why summer monsoons cause so much rain over land.

In the colder months, the cycle is reversed. Then the land cools faster than the oceans and the air over the land has higher pressure than air over the ocean. This causes the air over the land to flow to the ocean. When humid air rises over the ocean, it cools, and this causes precipitation over the oceans. (The cool air then flows towards the land to complete the cycle.)

Most summer monsoons have a dominant westerly component and a strong tendency to ascend and produce copious amounts of rain (because of the condensation of water vapor in the rising air). The intensity and duration, however, are not uniform from year to year. Winter monsoons, by contrast, have a dominant easterly component and a strong tendency to diverge, subside and cause drought.[16]

Similar rainfall is caused when moist ocean air is lifted upwards by mountains,[17] surface heating,[18] convergence at the surface,[19] divergence aloft, or from storm-produced outflows at the surface.[20] However the lifting occurs, the air cools due to expansion in lower pressure, and this produces condensation.

Global monsoon

Summary table

Location Monsoon/sub-system Average date of arrival Average date of withdrawal Notes
Northern Mexico North American/Gulf of California-Southwest USA late May[21] September incomplete wind reversal, waves
Tucson, Arizona, USA North American/Gulf of California-Southwest USA early July[21] September incomplete wind reversal, waves
Central America Central/South American Monsoon April[بحاجة لمصدر] October[بحاجة لمصدر] true monsoon
Amazon Brazil South American monsoon September[بحاجة لمصدر] May[بحاجة لمصدر]
Southeast Brazil South American monsoon November[بحاجة لمصدر] March[بحاجة لمصدر]
West Africa West African June 22[22] Sept[23] /October[22] waves
Southeast Africa Southeast Africa monsoon w/ Harmattan Jan[23] March[23]
Kerala, India Indian monsoon Jun 1[24] Dec 1[24] persistent
Mumbai, India Indian monsoon June 10[24] Oct 1[24]
Karachi, Pakistan Indian monsoon July 15[24] August[24]
Lahore, Pakistan Indian monsoon late July[24] Sep 1[24]
Phuket, Thailand Indo-Australian February/March December
Colombo, Sri Lanka Indo-Australian May 25[24] Dec 15[24] persistent
Bangkok, Thailand Indo-Australian/Indian-Indochina April–May October/November persistent
Yangon, Myanmar Indo-Australian/Indian-Indochina May 25[24] Nov 1[24]
Dhaka, Bangladesh Indo-Australian/Indian-Indochina mid-June October abrupt
Cebu, Philippines Indo-Australian/Borneo-Australian October March abrupt
Kelantan, Malaysia Indo-Australian/Borneo-Australian October March
Jakarta, Indonesia Indo-Australian/Borneo-Australian November March abrupt
Kaohsiung, Taiwan East Asian monsoon May 10[24]
Taipei, Taiwan East Asian monsoon May 20[24]
Hanoi, Vietnam East Asian monsoon May 20[24]
Kagoshima, Japan East Asian monsoon Jun 10[24]
Seoul, South Korea East Asian monsoon July 10[24]
Beijing, China East Asian monsoon July 20[24]
Darwin, Australia Australian monsoon Oct[23] April[23]


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أفريقيا

Southeast African monsoon clouds over Mayotte

The monsoon of western Sub-Saharan Africa is the result of the seasonal shifts of the Intertropical Convergence Zone and the great seasonal temperature and humidity differences between the Sahara and the equatorial Atlantic Ocean.[25] The ITCZ migrates northward from the equatorial Atlantic in February, reaches western Africa on or near June 22, then moves back to the south by October.[22] The dry, northeasterly trade winds, and their more extreme form, the harmattan, are interrupted by the northern shift in the ITCZ and resultant southerly, rain-bearing winds during the summer. The semiarid Sahel and Sudan depend upon this pattern for most of their precipitation.

أمريكا الشمالية

3-second video of a lightning strike within a thunderstorm over Island in the Sky, Canyonlands National Park

آسيا

الرياح الموسمية في آسيا الجنوبية

المقالة الرئيسية: رياح موسومية في جنوب آسيا
Onset dates and prevailing wind currents of the southwest summer monsoons in India.

الرياح الموسمية في جنوب آسيا، وهي من أصل مداري وترتبط بانخفاض شديد في الضغط الجوي فوق شمالي الهند، وتكون أشد عنفاً في فصل الصيف منها في فصل الشتاء، وفي الواقع ليست الرياح الموسمية الشتوية سوى الرياح التجارية العادية، وتسقط الرياح الموسمية الصيفية كميات هائلة من الأمطار في حالة مرور الرياح على مسطحات مائية ثم مقابلتها لمرتفعات، كما يحدث على الساحل الشرقي للهند وفي جزيرة سيلان.

Extreme difference is very much evident between wet and dry seasons in tropical seasonal forest. The image at left is taken at Bhawal National Park in central Bangladesh during dry season, and the right one is taken in wet monsoon season
Northeast monsoon
Monsoon clouds in Madhya Pradesh

Around September, with the sun retreating south, the northern landmass of the Indian subcontinent begins to cool off rapidly, and air pressure begins to build over northern India. The Indian Ocean and its surrounding atmosphere still hold their heat, causing cold wind to sweep down from the Himalayas and Indo-Gangetic Plain towards the vast spans of the Indian Ocean south of the Deccan peninsula. This is known as the Northeast Monsoon or Retreating Monsoon.

While travelling towards the Indian Ocean, the cold dry wind picks up some moisture from the Bay of Bengal and pours it over peninsular India and parts of Sri Lanka. Cities like Chennai, which get less rain from the Southwest Monsoon, receive rain from this Monsoon. About 50% to 60% of the rain received by the state of Tamil Nadu is from the Northeast Monsoon.[26] In Southern Asia, the northeastern monsoons take place from October to December when the surface high-pressure system is strongest.[27] The jet stream in this region splits into the southern subtropical jet and the polar jet. The subtropical flow directs northeasterly winds to blow across southern Asia, creating dry air streams which produce clear skies over India. Meanwhile, a low pressure system known as a monsoon trough develops over South-East Asia and Australasia and winds are directed toward Australia.

الرياح الموسمية في شرق آسيا

المقالة الرئيسية: رياح موسمية في شرق آسيا
سحب موسمية على كولكاتا
Monsoon floods in the Philippines

الرياح الموسمية الشرقية التي تؤثر في الصين واليابان وكوريا وتتصف بأنها أقوى في الشتاء منها في فصل الصيف، وفي كلا الفصلين ينقطع هبوب الرياح الموسمية أحياناً بسبب مرور المنخفضات الجوية في هذه العروض، وينجم عن الرياح الموسمية الشتوية انخفاض شديد في درجات الحرارة على طول سواحل شرقي آسيا.


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أستراليا

عاصفة ثلجية بالقرب من داروين، الأراضي الشمالية، أستراليا.

Also known as the Indo-Australian Monsoon. The rainy season occurs from September to February and it is a major source of energy for the Hadley circulation during boreal winter. The Maritime Continent Monsoon and the Australian Monsoon may be considered to be the same system, the Indo-Australian Monsoon.

It is associated with the development of the Siberian High and the movement of the heating maxima from the Northern Hemisphere to the Southern Hemisphere. North-easterly winds flow down Southeast Asia, are turned north-westerly/westerly by Borneo topography towards Australia. This forms a cyclonic circulation vortex over Borneo, which together with descending cold surges of winter air from higher latitudes, cause significant weather phenomena in the region. Examples are the formation of a rare low-latitude tropical storm in 2001, Tropical Storm Vamei, and the devastating flood of Jakarta in 2007.

The onset of the monsoon over the Maritime Continent tends to follow the heating maxima down Vietnam and the Malay Peninsula (September), to Sumatra, Borneo and the Philippines (October), to Java, Sulawesi (November), Irian Jaya and northern Australia (December, January). However, the monsoon is not a simple response to heating but a more complex interaction of topography, wind and sea, as demonstrated by its abrupt rather than gradual withdrawal from the region. The Australian monsoon (the "Wet") occurs in the southern summer when the monsoon trough develops over Northern Australia. Over three-quarters of annual rainfall in Northern Australia falls during this time.

اوروبا

انظر أيضاً: مناخ أوروبا

The European Monsoon (more commonly known as the return of the westerlies) is the result of a resurgence of westerly winds from the Atlantic, where they become loaded with wind and rain.[28] These westerly winds are a common phenomenon during the European winter, but they ease as spring approaches in late March and through April and May. The winds pick up again in June, which is why this phenomenon is also referred to as "the return of the westerlies".[29]

The rain usually arrives in two waves, at the beginning of June, and again in mid- to late June. The European monsoon is not a monsoon in the traditional sense in that it doesn't meet all the requirements to be classified as such. Instead, the return of the westerlies is more regarded as a conveyor belt that delivers a series of low-pressure centres to Western Europe where they create unsettled weather. These storms generally feature significantly lower-than-average temperatures, fierce rain or hail, thunder, and strong winds.[30]

The return of the westerlies affects Europe's Northern Atlantic coastline, more precisely Ireland, Great Britain, the Benelux countries, western Germany, northern France and parts of Scandinavia.

المناخ الموسمي

يتم وصف نوع المناخ أحياناً بالمناخ الموسمي، ويدل ذلك على مناخ المناطق التي تتصف بتغيرات موسمية في نظام الرياح، فمناطق الموسميات الرئيسة تمر مرتين في العام بحالات انعكاس في اتجاهات الرياح السائدة، وهذه الانعكاسات تؤدي إلى وجود فصلين محددين؛ أحدهما طويل غزير المطر تسقط فيه كمية من الأمطار تكفي لبقاء التربة، ولاسيما طبقة ما تحت التربة، محتفظة برطوبتها في السنة كلها، فتسمح بذلك بنمو الغابات المدارية الرطبة؛ وآخر قصير جاف.

ويعدّ المناخ المداري الموسمي مناخاً وسطاً بين المناخ المداري المطير ومناخ الساڤانا المداري بحيث يشبه المناخ المداري؛ المطير في كمية أمطاره السنوية ويشبه مناخ السافانا في التوزيع الفصلي للمطر. ويتوقف تحديد ما إذا كان المكان يتبع مناخ الساڤانا المداري أوالمناخ المداري الموسمي على أساس كمية ما يسقط من الأمطار في أثناء السنة كلها من ناحية وكمية المطر في أجفّ الشهور (أقل مطراً) من ناحية أخرى.

المصادر

  1. ^ عبد الجليل هويدي، محمد أحمد هيكل (2004). أساسيات الجيولوجيا التاريخية. مكتبة الدار العربية للكتب.
  2. ^ فاوز الموسى. "الموسميات". الموسوعة العربية. Retrieved 2012-06-25.
  3. ^ "Welcome to Monsoon Season – Why You Probably Are Using This Term Wrong". 29 June 2016. Archived from the original on 30 June 2016.
  4. ^ "Definition of Monsoon". 28 July 2016. Archived from the original on 19 July 2016.
  5. ^ Glossary of Meteorology (June 2000). "Monsoon". American Meteorological Society. Archived from the original on 2008-03-22. Retrieved 2008-03-14.
  6. ^ International Committee of the Third Workshop on Monsoons. The Global Monsoon System: Research and Forecast. Archived 2008-04-08 at the Wayback Machine Retrieved on 2008-03-16.
  7. ^ "Welcome to Monsoon Season – Why You Probably Are Using This Term Wrong". 29 June 2016. Archived from the original on 30 June 2016.
  8. ^ "Definition of Monsoon". 28 July 2016. Archived from the original on 19 July 2016.
  9. ^ Glossary of Meteorology (June 2000). "Monsoon". American Meteorological Society. Archived from the original on 2008-03-22. Retrieved 2008-03-14.
  10. ^ International Committee of the Third Workshop on Monsoons. The Global Monsoon System: Research and Forecast. Archived 2008-04-08 at the Wayback Machine Retrieved on 2008-03-16.
  11. ^ "Sea breeze – definition of sea breeze by The Free Dictionary". TheFreeDictionary.com.
  12. ^ Gadgil, Sulochana (2018). "The monsoon system: Land–sea breeze or the ITCZ?". Journal of Earth System Science (in الإنجليزية). 127 (1): 1. doi:10.1007/s12040-017-0916-x. ISSN 0253-4126.
  13. ^ Chou, C. (2003). "Land-sea heating contrast in an idealized Asian summer monsoon". Climate Dynamics. 21 (1): 11–25. Bibcode:2003ClDy...21...11C. doi:10.1007/s00382-003-0315-7. ISSN 0930-7575. S2CID 53701462.
  14. ^ "Liquids and Fluids – Specific Heats". Archived from the original on 2007-08-09. Retrieved 2012-10-01.
  15. ^ "Solids – Specific Heats". Archived from the original on 2012-09-22. Retrieved 2012-10-01.
  16. ^ "Monsoon". Britannica. Archived from the original on 2007-10-13. Retrieved 2007-05-15.
  17. ^ Dr. Michael Pidwirny (2008). CHAPTER 8: Introduction to the Hydrosphere (e). Cloud Formation Processes. Archived 2008-12-20 at the Wayback Machine Physical Geography. Retrieved on 2009-01-01.
  18. ^ Bart van den Hurk and Eleanor Blyth (2008). Global maps of Local Land–Atmosphere coupling. Archived 2009-02-25 at the Wayback Machine KNMI. Retrieved on 2009-01-02.
  19. ^ Robert Penrose Pearce (2002). Meteorology at the Millennium. Archived 2016-04-27 at the Wayback Machine Academic Press, p. 66. ISBN 978-0-12-548035-2. Retrieved on 2009-01-02.
  20. ^ Glossary of Meteorology (June 2000). "Gust Front". American Meteorological Society. Archived from the original on 2011-05-05. Retrieved 2008-07-09.
  21. ^ أ ب "Southwest Monsoon 2017 Forecast: Warmer-Than-Average Conditions Could Lead to More Storms". Archived from the original on 2017-06-06. Retrieved 2017-06-06.
  22. ^ أ ب ت Innovations Report. Monsoon in West Africa: Classic continuity hides a dual-cycle rainfall regime. Archived 2011-09-19 at the Wayback Machine Retrieved on 2008-05-25.
  23. ^ أ ب ت ث ج "West African monsoon". Archived from the original on 2016-06-25. Retrieved 2017-06-06.
  24. ^ أ ب ت ث ج ح خ د ذ ر ز س ش ص ض ط ظ ع "Indian monsoon | meteorology". Archived from the original on 2016-08-01. Retrieved 2017-06-06.
  25. ^ African Monsoon Multidisciplinary Analyses (AMMA). "Characteristics of the West African Monsoon". AMMA. Archived from the original on July 12, 2007. Retrieved 2009-10-15.
  26. ^ "NORTHEAST MONSOON". Archived from the original on 2015-12-29. Retrieved 2011-11-07.
  27. ^ Robert V. Rohli; Anthony J. Vega (2007). Climatology. Jones & Bartlett Publishers. p. 204. ISBN 978-0-7637-3828-0. Retrieved 2009-07-19.
  28. ^ Visser, S.W. (1953). Some remarks on the European monsoon. Birkhäuser: Basel.
  29. ^ Leo Hickman (2008-07-09). "The Question: What is the European monsoon?". The Guardian. Archived from the original on 2013-09-02. Retrieved 2009-06-09.
  30. ^ Paul Simons (2009-06-07). "'European Monsoon' to blame for cold and rainy start to June". The Times. Archived from the original on 2011-06-04. Retrieved 2009-06-09.

المراجع

  • جهاد الشاعر، جغرافية المناخ (مطبوعات جامعة دمشق 2005).
  • علي موسى، المناخ الإقليمي (منشورات جامعة دمشق، 1990).
  • يوسف عبد المجيد فايد، جغرافية المناخ والنبات (دار النهضة العربية، القاهرة 1995).
  • R.G.BARRY, and R. J. CHORLEY. Atmosphere, Weathr, and Climat (2003).
  • WEBSTER, P. J., T. PALMER, M. YANAI, V. MAGANA, J. SHUKLA and T. YASUNARI, Monsoons: Processes and predictability and prospect for prediction. J. Geophys. Res. Special Issues, 103 (C7), 14451-14510,. (1998).

قراءات للإستزادة

وصلات خارجية

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معرفة المصادر بها نص من the 1911 Encyclopædia Britannica مقالة Monsoon.
جزء من سلسلة الطبيعة عن
الطقس
Global tropical cyclone tracks-edit2.jpg
الفصول
المواسم المدارية
العواصف
التساقط
موضوعات
المعاجم
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