The westerlies (blue arrows) and trade winds (yellow arrows)^{[dubious – discuss]}

The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator.^[1] The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Historically, the trade winds have been used by captains of sailing ships to cross the world's oceans for centuries, and enabled European empire expansion into the Americas and trade routes to become established across the Atlantic and Pacific oceans.

In meteorology, the trade winds 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, respectively. Trade winds also steer African dust westward across the Atlantic ocean into the Caribbean sea, as well as portions of southeastern North America. Shallow cumulus clouds are seen within trade wind regimes, and are capped from becoming taller by a trade wind inversion, which is caused by descending air aloft from within the subtropical ridge. The weaker the trade winds become, the more rainfall can be expected within neighboring landmasses.

History[link]

A Spanish galleon

The term trade winds originally derives from the early fourteenth century late Middle English word 'trade' meaning "path" or "track."^[2] The Portuguese recognized the importance of the trade winds in navigation in the Atlantic ocean as early as the 15th century.^[3] The full wind circulation, which included both the trade wind easterlies and higher-latitude Westerlies, was un-known (to Europeans) across the Pacific ocean until Andres de Urdaneta's voyage in 1565.^[4]

The captain of a sailing ship seeks a course along which the winds can be expected to blow in the direction of travel.^[5] During the Age of Sail the pattern of prevailing winds made various points of the globe easy or difficult to access, and therefore had a direct impact on European empire-building and thus on modern political geography. For example, Manila galleons could not sail into the wind at all.^[4]

By the 18th century the importance of the trade winds to England's merchant fleet for crossing the Atlantic Ocean had led both the general public and etymologists to identify the name with a later meaning of 'trade', "(foreign) commerce".^[6] Between 1847 and 1849, Matthew Fontaine Maury collected enough information to create wind and current charts for the world's oceans.^[7]

Cause[link]

3D map showing Hadley cells in relationship to trade winds on the surface.

As part of the Hadley cell circulation, surface air flows toward the equator while the flow aloft is towards the poles. A low-pressure area of calm, light variable winds near the equator is known as the doldrums,^[8] equatorial trough,^[9] intertropical front, or the Intertropical Convergence Zone.^[10] When located within a monsoon region, this zone of low pressure and wind convergence is also known as the monsoon trough.^[11] Around 30° in both hemispheres air begins to descend toward the surface in subtropical high-pressure belts known as subtropical ridges. The subsident (sinking) air is relatively dry because, as it descends, the temperature increases but the absolute humidity remains constant, which lowers the relative humidity of the air mass. This warm, dry air is known as a superior 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 trade wind inversion.^[12]

The surface air that flows from these subtropical high-pressure belts toward the Equator is deflected toward the west in both hemispheres by the Coriolis effect.^[13] These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere.^[14] Because winds are named for the direction from which the wind is blowing,^[15] these winds are called the northeasterly trade winds in the Northern Hemisphere and the southeasterly trade winds in the Southern Hemisphere. The trade winds meet at the doldrums.^[8]

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.^[16] Maritime tropical air masses are sometimes referred to as trade air masses.^[17] The one region of the Earth which has an absence of trade winds is the north Indian ocean.^[18]

Weather effects[link]

Nā Pali coast, Kauaʻi, showing trade wind cumuli

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.^[19] 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.^[20] As an example, the windy season in the Guianas, which lie at low latitudes in South America, occurs between January and April.^[21] 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.^[22] When the trade winds are weaker, more extensive areas of rain fall upon landmasses within the tropics, such as Central America.^[23]

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. 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.^[24] Over 50% of the African dust that reaches the United States affects Florida.^[25] 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.^[26] Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s.^[27]

See also[link]

• Intertropical Convergence Zone
• Westerlies

References[link]

David Maslanka (born August 30, 1943, in New Bedford, Massachusetts) is a U.S. composer who writes for a variety of genres, including works for choir, wind ensemble, chamber music and symphony orchestra.

Best-known for his highly acclaimed wind ensemble compositions, Maslanka has published nearly 100 pieces, including nine symphonies, seven of them for concert band, nine concerti and a full Mass. Maslanka’s compositional style is rhythmically intense and extremely complex, yet possesses an underlying delicate beauty. He works from a meditative standpoint of spiritual inspiration, and this gentle, warm quality permeates his music. Maslanka’s compositions have been performed throughout the United States and Europe, as well as Australia, Canada and Japan (Savoie 2003).

See full list of compositions by David Maslanka.

Life[link]

Maslanka received his Bachelor of Music from the Oberlin Conservatory (1961–1965) and went on to earn a Master of Music and Doctor of Philosophy from Michigan State University (1965–71). During his undergraduate work, Maslanka also spent one year studying abroad at the Mozarteum in Salzburg, Austria (1963–64). While attending Michigan State University, Maslanka studied composition with H. Owen Reed (Maslanka 2004). He served over 20 years on the faculty at Kingsborough Community College of the City University of New York and has also served on the faculty at Sarah Lawrence College, New York University (Maslanka 2005^{[Full citation needed]}). Dr. Maslanka is a freelance composer and has worked solely on commission since 1990. He currently lives in Missoula, Montana.

Awards and honors[link]

Dr. Maslanka has received five residence fellowships at the MacDowell Colony in Peterborough, New Hampshire (1974, 1975, 1978, 1979, and 1982), as well as generous grants from the University of Connecticut Research Foundation, the American Music Center, the Martha Baird Rockefeller Fund for Music, the State University of New York Research Foundation and the American Society of Composers, Authors, and Publishers (ASCAP). He has earned the National Endowment for the Arts Composer Award three times (1974, ‘75 and ‘89) (Carl Fischer 2005). In 1999, he was awarded the National Symphony Orchestra regional composer-in-residence award. Since 1980, Maslanka has served as a guest composer for over 100 universities, music festivals and conferences (Maslanka 2005^{[Full citation needed]}).

He is a National Patron of Delta Omicron, an international professional music fraternity (Delta Omicron International Music Fraternity 2011).^{[not in citation given]}

Works[link]

Many of Maslanka’s compositions for winds and percussion have become established pieces in band repertoire. Among these pieces are “A Child’s Garden of Dreams,” “Rollo Takes a Walk,” and numerous concertos featuring a wide variety of solo instruments, including euphonium, flute, piano, marimba, alto saxophone and (most recently) trombone. Maslanka’s second and fourth symphonies have become particularly popular wind literature. His works for percussion include “Montana Music: Three Dances for Percussion,” “Variations of ‘Lost Love,’” “My Lady White,” “Arcadia II: Concerto for Marimba and Percussion Ensemble” and “Crown of Thorns.” Maslanka has also written a complete Mass for full choir, soprano and baritone soli, with accompaniment by full symphonic band. Having spent his childhood in the New England area, a number of Maslanka’s compositions were influenced by his close relationship with the ocean (Alexander 1998). “Sea Dreams,” for example, as well as the second movement of his second symphony, reference large bodies of water. Maslanka’s works have been recorded and produced primarily by Albany Records, as well as Cambria, Crest, CRI, Klavier, Mark, Novisse, St. Olaf and Umass labels. Most of his music is published by Carl Fischer. See full list of compositions by David Maslanka.

Quotes[link]

In a letter to a young composer, Dr. Maslanka shared some ideas on his compositional style and method:

You ask about the soul nature of music, and are music and soul the same thing. Music is one of the expressions of soul. A person does not have to be consciously aware of soul connection for soul force to be expressed through that person. The conscious mind and the deep unconscious are two different things, but everyone has both of them. The unconscious can push its way into consciousness unbidden. Often this makes people do neurotic or crazy things – compulsive behavior of one kind or another. If a person is prepared artistically, then a sudden eruption of soul force might appear as a composition or a powerful performance. The person may have no idea where the force came from. This was my experience as a young composer. As I gained technical skill there would be sudden bursts of music that 'appeared.' There was always the hard work of getting it composed properly, but fairly early on I learned to follow my instincts when something powerful began to happen. The impulse to write, having a 'true voice', and having the necessary technical equipment are all different issues. There are fine technicians who have no true voice, and people with true voice who have struggled with technique.

—(Maslanka 2005^{[Full citation needed]})

Further reading[link]

• Hippensteel, Scott A. A Study of David Maslanka’s “Unending Stream of Life”. 2011.

References[link]

• Alexander, Peter. 1998. UI School of Music performance will feature simultaneous world premiere April 7. Press Release. University of Iowa. March 27.
• Carl Fischer LLC. 2005. David Maslanka: Biography.
• Delta Omicron International Music Fraternity. 2011. "Welcome To Delta Omicron International Music Fraternity". Delta Omicron website, edited & maintained by Whitney Mullins. (Accessed 26 March 2012).
• Maslanka, David. 2004. Composers on Composing for Band. Ed. Mark Camphouse. GIA Publishing Inc.. Chicago. p. 197-224.
• Maslanka, David. Personal web page. http://www.davidmaslanka.com
• Phillips, Paul. 2001. "Maslanka, David". New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell, 16:30. London: Macmillan Publishers.
• Savoie, Bernard. 2003. David Maslanka