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Trade winds
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Main page The trade winds or easterlies are the permanent east-
Contents to-west prevailing winds that flow in the Earth's equatorial
Current events region (between 30°N and 30°S latitudes). The trade winds
Random article blow mainly from the northeast in the Northern Hemisphere
About Wikipedia and from the southeast in the Southern Hemisphere,
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strengthening during the winter and when the Arctic
Donate
oscillation is in its warm phase. Trade winds have been
The westerlies (blue arrows) and trade winds
Contribute used by captains of sailing ships to cross the world's (yellow and brown arrows)
Help oceans for centuries and enabled colonial expansion into
Learn to edit the Americas and trade routes to become established
Community portal across the Atlantic and Pacific oceans.
Recent changes
Upload file In meteorology, they act as the steering flow for tropical storms that form over the Atlantic, Pacific, and southern
Indian Oceans and make landfall in North America, Southeast Asia, and Madagascar and eastern Africa.
Tools Shallow cumulus clouds are seen within trade wind regimes and are capped from becoming taller by a trade
What links here wind inversion, which is caused by descending air aloft from within the subtropical ridge. The weaker the trade
Related changes winds become, the more rainfall can be expected in the neighboring landmasses.
Special pages
Permanent link The trade winds also transport nitrate- and phosphate-rich Saharan dust to all Latin America but the southwest,
Page information to the Caribbean Sea, and to parts of southeastern North America.
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Wikidata item Contents [hide]
1 History
Print/export
2 Cause
Download as PDF 3 Weather and biodiversity effects
Languages 4 See also
5 References
Afrikaans
‫اﻟﻌرﺑﯾﺔ‬
Asturianu
Azərbaycanca History [edit]
See also: Age of Discovery, Volta do Mar, and Age of sail
Bân-lâm-gú
Беларуская The term originally derives from the early fourteenth century sense of trade
Български (in late Middle English) still often meaning "path" or "track".[1] The
Bosanski Portuguese recognized the importance of the trade winds (then the Volta
Català do mar, meaning in Portuguese "turn of the sea" but also "return from the
Čeština sea") in navigation in both the north and south Atlantic ocean as early as
Dansk
the 15th century.[2] From West Africa, the Portuguese had to sail away from
Deutsch
Eesti
continental Africa, that is, to west and northwest. They could then turn
Ελληνικά northeast, to the area around the Azores islands, and finally east to
Español mainland Europe. They also learned that to reach South Africa, they
Esperanto needed to go far out in the ocean, head for Brazil, and around 30°S go
Euskara east again. (This is because following the African coast southbound means
‫ﻓﺎرﺳﯽ‬ sailing upwind in the Southern hemisphere.) In the Pacific ocean, the full
Français A Spanish galleon
wind circulation, which included both the trade wind easterlies and higher-
Gaeilge
Galego latitude Westerlies, was unknown to Europeans until Andres de Urdaneta's
voyage in 1565.[3]
Հայերեն The captain of a sailing ship seeks a course along which the winds can be expected to blow in the direction of
travel.[4] During the Age of Sail, the pattern of prevailing winds made various points of the globe easy or difficult
Hrvatski
Ido to access, and therefore had a direct effect on European empire-building and thus on modern political
Bahasa Indonesia geography. For example, Manila galleons could not sail into the wind at all.[3]
Ирон By the 18th century, the importance of the trade winds to England's merchant fleet for crossing the Atlantic
Íslenska
Ocean had led both the general public and etymologists to identify the name with a later meaning of "trade": "
Italiano
‫עברית‬ (foreign) commerce".[5] Between 1847 and 1849, Matthew
Fontaine Maury collected enough information to create wind
Қазақша and current charts for the world's oceans.[6]
Kreyòl ayisyen
Latina
Latviešu Cause [edit] Edmond Halley's map of the trade winds,
Lietuvių See also: Air mass, Hadley cell, Humidity, Intertropical 1686
Limburgs
Convergence Zone, Monsoon, Monsoon trough, Near-
Magyar
Македонски equatorial trough, and Prevailing winds
As part of the Hadley cell, surface air flows
Bahasa Melayu toward the equator while the flow aloft is
မ န မာဘာသာ towards the poles. A low-pressure area of
Nederlands
日本語 calm, light variable winds near the equator
Nordfriisk is known as the doldrums,[7] near-
Norsk bokmål equatorial trough,[8] intertropical front, or
Norsk nynorsk the Intertropical Convergence Zone.[9]
Occitan When located within a monsoon region, this
Oʻzbekcha/ўзбекча
zone of low pressure and wind
Polski
Português convergence is also known as the
Română monsoon trough.[10] Around 30° in both
Русский hemispheres, air begins to descend toward
Shqip the surface in subtropical high-pressure
Slovenčina belts known as subtropical ridges. The
Slovenščina 3D map showing Hadley cells in relationship to trade winds on the
subsident (sinking) air is relatively dry
Српски / srpski surface.
Srpskohrvatski /
because as it descends, the temperature
српскохрватски increases, but the moisture content
Suomi remains constant, which lowers the relative humidity of the air mass. This warm, dry air is known as a superior
Svenska air mass and normally resides above a maritime tropical (warm and moist) air mass. An increase of temperature
with height is known as a temperature inversion. When it occurs within a trade wind regime, it is known as a
ไทย
Türkçe trade wind inversion.[11]
Українська The surface air that flows from these subtropical high-pressure belts toward the Equator is deflected toward the
Tiếng Việt west in both hemispheres by the Coriolis effect.[12] These winds blow predominantly from the northeast in the
吴语
Northern Hemisphere and from the southeast in the Southern Hemisphere.[13] Because winds are named for the
粵語
中文 direction from which the wind is blowing,[14] these winds are called the northeasterly trade winds in the Northern
Edit links Hemisphere and the southeasterly trade winds in the Southern Hemisphere. The trade winds of both
hemispheres meet at the Doldrums.[7]
As they blow across tropical regions, air masses heat up over lower latitudes due to more direct sunlight. Those
that develop over land (continental) are drier and hotter than those that develop over oceans (maritime), and
travel northward on the western periphery of the subtropical ridge.[15] Maritime tropical air masses are
sometimes referred to as trade air masses.[16] All tropical oceans except the northern Indian Ocean have
extensive areas of trade winds.[17]

Weather and biodiversity effects [edit]

Clouds which form above regions within trade wind regimes are typically composed of cumulus which extend no
more than 4 kilometres (13,000 ft) in height, and are capped from being taller by the trade wind inversion.[18]
Trade winds originate more from the direction of the poles (northeast in the Northern Hemisphere, southeast in
the Southern Hemisphere) during the cold season, and are stronger in the winter than the summer.[19] As an
example, the windy season in the Guianas, which lie at low latitudes in South America, occurs between January
and April.[20] When the phase of the Arctic oscillation (AO) is warm, trade winds are stronger within the tropics.
The cold phase of the AO leads to weaker trade winds.[21] When the trade winds are weaker, more extensive
areas of rain fall upon landmasses within the tropics, such as Central America.[22]
During mid-summer in the Northern Hemisphere (July), the westward-moving trade winds south of the
northward-moving subtropical ridge expand northwestward from the Caribbean sea into southeastern North
America (Florida and Gulf Coast). When dust from the Sahara moving around the southern periphery of the
ridge travels over land, rainfall is suppressed and the sky changes from a blue to a white appearance which
leads to an increase in red sunsets. Its presence negatively impacts air quality by adding to the count of
airborne particulates.[23] Although the Southeast USA has some of the cleanest air in North America, much of
the African dust that reaches the United States affects Florida.[24] Since 1970, dust outbreaks have worsened
due to periods of drought in Africa. There is a large variability in the dust transport to the Caribbean and Florida
from year to year.[25] Dust events have been linked to a decline in the health of coral reefs across the
Caribbean and Florida, primarily since the 1970s.[26]
Every year, millions of tons of nutrient-rich Saharan dust cross the Atlantic Ocean, bringing vital phosphorus
and other fertilizers to depleted Amazon soils.[27]

See also [edit]

Intertropical Convergence Zone
Volta do mar
Westerly wind burst
Winds in the Age of Sail

References [edit]
1. ^ Carol G. Braham; Enid Pearsons; Deborah M. Posner; Georgia S. Maas & Richard Goodman (2001). Random
House Webster's College Dictionary (second ed.). Random House. p. 1385 . ISBN 978-0-375-42560-8.
2. ^ Hermann R. Muelder (2007). Years of This Land - A Geographical History of the United States . Read Books.
p. 38. ISBN 978-1-4067-7740-6.
3. ^ a b Derek Hayes (2001). Historical atlas of the North Pacific Ocean: maps of discovery and scientific exploration,
1500–2000 . Douglas & McIntyre. p. 18. ISBN 978-1-55054-865-5.
4. ^ Cyrus Cornelius Adams (1904). A text-book of commercial geography . D. Appleton and company. p. 19 .
5. ^ Oxford English Dictionary (2 ed.). p. 225.
6. ^ Derek Hayes (2001). Historical atlas of the North Pacific Ocean: maps of discovery and scientific exploration,
1500–2000 . Douglas & McIntyre. p. 152. ISBN 978-1-55054-865-5.
7. ^ a b Sverre Petterssen (1941). Introduction to Meteorology . Mcgraw-Hill Book Company, Inc. p. 110. ISBN 978-
1-4437-2300-8.
8. ^ Glossary of Meteorology (June 2000). "Doldrums" . American Meteorological Society. Archived from the
original on 2009-09-25. Retrieved 2009-11-09.
9. ^ Glossary of Meteorology (June 2000). "Intertropical Convergence Zone" . American Meteorological Society.
Archived from the original on 2009-06-02. Retrieved 2009-11-09.
10. ^ Glossary of Meteorology (June 2000). "Monsoon Trough" . American Meteorological Society. Archived from the
original on 2009-06-17. Retrieved 2009-11-09.
11. ^ Glossary of Meteorology (June 2000). "Superior air" . American Meteorological Society. Archived from the
original on 2011-06-06. Retrieved 2009-10-28.
12. ^ Glossary of Meteorology (2009). "trade winds" . Glossary of Meteorology. American Meteorological Society.
Archived from the original on 2008-12-11. Retrieved 2008-09-08.
13. ^ Ralph Stockman Tarr; Frank Morton McMurry; Almon Ernest Parkins (1909). Advanced geography . State
Printing. p. 246 .
14. ^ JetStream (2008). "How to read weather maps" . National Weather Service. Archived from the original on
2012-07-05. Retrieved 2007-05-16.
15. ^ Glossary of Meteorology (June 2000). "Tropical air" . American Meteorological Society. Archived from the
original on 2011-06-06. Retrieved 2009-10-28.
16. ^ Glossary of Meteorology (June 2000). "Trade air" . American Meteorological Society. Archived from the
original on 2011-06-06. Retrieved 2009-10-28.
17. ^ John E. Oliver (2005). Encyclopedia of world climatology . Springer. p. 128. ISBN 978-1-4020-3264-6.
18. ^ Bob Rauber (2009-05-22). "Research-The Rain in Cumulus over the Ocean Campaign" . Retrieved 2009-11-08.
19. ^ James P. Terry (2007). Tropical cyclones: climatology and impacts in the South Pacific . Springer. p. 8.
ISBN 978-0-387-71542-1.
20. ^ G. E. Pieter & F. Augustinus (2004). "The influence of the trade winds on the coastal development of the
Guianas at various scale levels: a synthesis". Marine Geology. 208 (2–4): 145–151.
Bibcode:2004MGeol.208..145A . doi:10.1016/j.margeo.2004.04.007 . hdl:1874/12170 .
21. ^ Robert R. Steward (2005). "The Ocean's Influence on North American Drought" . Texas A&M University.
22. ^ John E. Oliver (2005). Encyclopedia of world climatology . Springer. p. 185. ISBN 978-1-4020-3264-6.
23. ^ Science Daily (1999-07-14). African Dust Called A Major Factor Affecting Southeast U.S. Air Quality. Retrieved
on 2007-06-10.
24. ^ Science Daily (2001-06-15). Microbes And The Dust They Ride In On Pose Potential Health Risks. Retrieved
on 2007-06-10.
25. ^ Usinfo.state.gov (2003). Study Says African Dust Affects Climate in U.S., Caribbean. Archived 2007-06-20
at the Wayback Machine Retrieved on 2007-06-10.
26. ^ U. S. Geological Survey (2006). Coral Mortality and African Dust. Retrieved on 2007-06-10.
27. ^ Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, Lorraine A.; Prospero, Joseph M.; Omar, Ali;
Winker, David; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo; Zhao, Chun (2015). "The fertilizing role of African dust in
the Amazon rainforest: A first multiyear assessment based on data from Cloud‐Aerosol Lidar and Infrared
the Amazon rainforest: A first multiyear assessment based on data from Cloud‐Aerosol Lidar and Infrared
Pathfinder Satellite Observations". Geophysical Research Letters. 42 (6): 1984–1991.
doi:10.1002/2015GL063040 . Lay summary – ScienceDaily (February 24, 2015).
 Categories: Climate patterns Atmospheric dynamics Wind Age of Sail

This page was last edited on 12 December 2020, at 15:35 (UTC).

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