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| Southeast Trade Winds | |
|---|---|
| Name | Southeast Trade Winds |
| Type | Trade wind |
| Location | Tropical Southern Hemisphere |
| Dominant direction | Southeast to Northwest |
| Typical seasons | Austral summer to autumn |
| Related systems | Hadley Cell, Intertropical Convergence Zone, South Pacific Convergence Zone |
Southeast Trade Winds
The Southeast Trade Winds are persistent surface winds of the tropical Southern Hemisphere that blow from the southeast toward the equator, influencing Indian Ocean, Pacific Ocean, Atlantic Ocean, Australia, Madagascar, and South America. They are a key component of the Hadley Cell, interact with the Intertropical Convergence Zone, and affect phenomena such as the El Niño–Southern Oscillation, South Pacific Convergence Zone, Monsoon of South Asia, and regional maritime navigation like routes to Cape Town. Their variability shapes climates across Brazil, Argentina, Chile, Indonesia, and the Philippines.
The Southeast Trade Winds are defined as steady low-level winds that typically blow from the southeast in the subtropical to tropical belt of the Southern Hemisphere, often between about 5°S and 30°S, connecting regions such as South Africa, New Zealand, Fiji, Papua New Guinea, and New Caledonia. Characteristic features include relatively uniform direction influenced by the Coriolis effect near the Equator and modulated speed related to the position of the Intertropical Convergence Zone and the strength of the Hadley Cell. Their climatological role is comparable to the Northeast Trade Winds of the Northern Hemisphere and they contribute to trade routes historically used by vessels such as those of the Dutch East India Company and explorers like James Cook and Ferdinand Magellan.
Formation is driven by hemispheric circulation tied to the Hadley Cell and differential heating between the Tropic of Capricorn and the equatorial belt near the Intertropical Convergence Zone. Air subsiding in the subtropics over regions like the South Atlantic High, South Pacific High, and Indian Ocean High flows equatorward and is deflected by the Coriolis effect, producing the southeast-to-northwest trajectory toward convergence zones near the Amazon Basin and Congo Basin analogues. Seasonal shifts in solar declination move the Subtropical Ridge and modify pressure gradients that intensify or weaken trades, interacting with teleconnections such as Southern Annular Mode and Madden–Julian Oscillation. Oceanic sea surface temperature patterns linked to El Niño and La Niña alter convection and feedback on wind strength.
Spatially, these winds dominate the tropical and subtropical belts of the South Pacific Ocean, South Atlantic Ocean, and Indian Ocean, touching coastlines of Brazil, Uruguay, Namibia, Mozambique, Western Australia, and New Zealand. Seasonally they strengthen during austral summer when the Intertropical Convergence Zone shifts poleward and the subtropical highs consolidate over regions like the Great Australian Bight and South Atlantic High. Variability arises from events including El Niño–Southern Oscillation phases, the Antarctic ozone hole influences on the Southern Annular Mode, and episodic phenomena such as Southern Hemisphere tropical cyclones that can locally disrupt trade flow.
Southeast trades drive ocean surface currents including parts of the South Equatorial Current, Brazil Current interactions, and elements of the West Wind Drift, affecting upwelling along coasts like Peru and Namibia and modulating sea surface temperatures that influence fisheries such as those off Galápagos Islands and the Benguela Current. Their persistence contributes to arid climates in regions adjacent to the subtropical highs, shaping environments in the Atacama Desert, Kalahari Desert, and portions of Western Australia. Trades also influence regional precipitation patterns over basins like the Amazon Basin and affect heat transport that links to global circulations studied at institutions including National Oceanic and Atmospheric Administration, Commonwealth Scientific and Industrial Research Organisation, and Meteorological Service of New Zealand.
These winds interact with large-scale systems including the Intertropical Convergence Zone, South Pacific Convergence Zone, mid-latitude westerlies, and transient features such as tropical cyclones and ex-tropical cyclones that recurve from the subtropics. Shear between trades and monsoonal flows contributes to convective organization relevant to storms affecting Queensland, Vanuatu, and Fiji. Teleconnections with El Niño and La Niña modify the frequency and intensity of rainfall extremes and droughts across Southeast Asia, Southern Africa, and South America, with documented societal impacts during notable events like the 1997–98 El Niño and 2010–11 La Niña.
Historically the Southeast Trade Winds enabled maritime exploration and commerce by powers such as the Portuguese Empire, Spanish Empire, and Dutch East India Company, shaping colonial-era routes between Europe, Africa, Asia, and Americas. Cultural narratives in maritime communities of Polynesia, Melanesia, and coastal South America reference trade wind patterns in oral histories and navigation practices alongside figures like Thor Heyerdahl who studied Pacific voyaging. The winds influenced agricultural calendars in regions governed by institutions like the British East India Company and played roles in historical events including voyages of Christopher Columbus's contemporaries and the sailing of HMS Endeavour.
Observation employs satellites from programs like NASA and European Space Agency, in-situ networks including Argo (ocean profiling floats), moored buoys from the Global Drifter Program, and ship-based reports coordinated by agencies such as World Meteorological Organization, Met Office (United Kingdom), and Bureau of Meteorology (Australia). Measurements utilize scatterometers on satellites such as QuikSCAT predecessors and successors, radiosonde launches from stations in Pagan Island, Diego Garcia, and Ascension Island-region analogues, and reanalysis datasets from centers like ECMWF and NOAA National Centers for Environmental Prediction. Paleoclimate records from coral reef proxies, sediment cores off Vanuatu and Galápagos Islands, and historical ship logbooks archived at institutions like the National Archives (United Kingdom) assist reconstructions of past trade wind variability.
Category:Winds