Mean sea level (MSL) is a measure of the average height of the ocean's surface (such as the halfway point between the mean high tide and the mean low tide); used as a standard in reckoning land elevation. MSL also plays an extremely important role in aviation, where standard sea level pressure is used as the measurement datum of altitude at flight levels.

Measurement

To an operator of a tide gauge, MSL means the "still water level"—the level of the sea with motions such as wind waves averaged out—averaged over a period of time such that changes in sea level, e.g., due to the tides, also get averaged out. One measures the values of MSL in respect to the land. Hence a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates.

In the UK, mean sea level has been measured at Newlyn in Cornwall and Liverpool for decades, by tide gauges to provide Ordnance Datum for the ''zero metres'' height on UK maps.

Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008.

Difficulties in utilization

To extend this definition far from the sea means comparing the local height of the mean sea surface with a "level" reference surface, or datum, called the geoid. In a state of rest or absence of external forces, the mean sea level would coincide with this geoid surface, being an equipotential surface of the Earth's gravitational field. In reality, due to currents, air pressure variations, temperature and salinity variations, etc., this does not occur, not even as a long term average. The location-dependent, but persistent in time, separation between mean sea level and the geoid is referred to as (stationary) ocean surface topography. It varies globally in a range of ± 2 m.

Traditionally, one had to process sea-level measurements to take into account the effect of the 228-month Metonic cycle and the 223-month eclipse cycle on the tides. Mean sea level is not constant over the surface of the Earth. For instance, mean sea level at the Pacific end of the Panama Canal stands higher than at the Atlantic end.

Sea level and dry land

Several terms are used to describe the changing relationships between sea level and dry land. When the term "relative" is used, it means change relative to a fixed point in the sediment pile. The term "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps. The term "steric" refers to global changes in sea level due to thermal expansion and salinity variations. The term "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or tectonic effects; it implies no change in the volume of water in the oceans. The melting of glaciers at the end of ice ages is one example of eustatic sea level rise. The subsidence of land due to the withdrawal of groundwater is an isostatic cause of relative sea level rise. Paleoclimatologists can track sea level by examining the rocks deposited along coasts that are very tectonically stable, like the east coast of North America. Areas like volcanic islands are experiencing relative sea level rise as a result of isostatic cooling of the rock which causes the land to sink.

On other planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level", serves equivalently as a reference for the height of planetary features.

Sea level change

Local and eustatic sea level

Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time (such as a month or a year) long enough that fluctuations caused by waves and tides are smoothed out. One must adjust perceived changes in LMSL to account for vertical movements of the land, which can be of the same order (mm/yr) as sea level changes. Some land movements occur because of isostatic adjustment of the mantle to the melting of ice sheets at the end of the last ice age. The weight of the ice sheet depresses the underlying land, and when the ice melts away the land slowly rebounds. Changes in ground-based ice volume also affect local and regional sea levels by the readjustment of the geoid and true polar wander. Atmospheric pressure, ocean currents and local ocean temperature changes can affect LMSL as well.

Eustatic change (as opposed to local change) results in an alteration to the global sea levels due to changes in either the volume of water in the world oceans or net changes in the volume of the ocean basins.

Short term and periodic changes

There are many factors which can produce short-term (a few minutes to 14 months) changes in sea level.

{| ! colspan="3" style="background:lightgray" | Periodic sea level changes |- | Diurnal and semidiurnal astronomical tides || 12–24 h P || 0.2–10+ m |- | Long-period tides ||   ||   |- | Rotational variations (Chandler wobble) || 14 month P |- ! colspan="3" style="background:lightgray" | Meteorological and oceanographic fluctuations |- | Atmospheric pressure || Hours to months || –0.7 to 1.3 m |- | Winds (storm surges) || 1–5 days || Up to 5 m |- | Evaporation and precipitation (may also follow long-term pattern) || Days to weeks ||   |- | Ocean surface topography (changes in water density and currents) || Days to weeks || Up to 1 m |- | El Niño/southern oscillation || 6 mo every 5–10 yr || Up to 0.6 m |- ! colspan="3" style="background:lightgray" | Seasonal variations |- | Seasonal water balance among oceans (Atlantic, Pacific, Indian) ||   ||   |- | Seasonal variations in slope of water surface ||   ||   |- | River runoff/floods || 2 months || 1 m |- | Seasonal water density changes (temperature and salinity) || 6 months || 0.2 m |- ! colspan="3" style="background:lightgray" | Seiches |- | Seiches (standing waves) || Minutes to hours || Up to 2 m |- ! colspan="3" style="background:lightgray" | Earthquakes |- | Tsunamis (generate catastrophic long-period waves) || Hours || Up to 10 m |- | Abrupt change in land level || Minutes || Up to 10 m |}

Long term changes

Various factors affect the volume or mass of the ocean, leading to long-term changes in eustatic sea level. The two primary influences are temperature (because the volume of water depends on temperature), and the mass of water locked up on land and sea as fresh water in rivers, lakes, glaciers, polar ice caps, and sea ice. Over much longer geological timescales, changes in the shape of the oceanic basins and in land/sea distribution will affect sea level.

Observational and modelling studies of mass loss from glaciers and ice caps indicate a contribution to sea-level rise of 0.2 to 0.4 mm/yr averaged over the 20th century.

Glaciers and ice caps

Each year about 8 mm (0.3 inch) of water from the entire surface of the oceans falls into the Antarctica and Greenland ice sheets as snowfall. If no ice returned to the oceans, sea level would drop 8 mm every year. To a first approximation, the same amount of water appeared to return to the ocean in icebergs and from ice melting at the edges. Scientists previously had estimated which is greater, ice going in or coming out, called the mass balance, important because it causes changes in global sea level. High-precision gravimetry from satellites in low-noise flight has since determined Greenland is losing billions of tons per year, in accordance with loss estimates from ground measurement.

Ice shelves float on the surface of the sea and, if they melt, to first order they do not change sea level. Likewise, the melting of the northern polar ice cap which is composed of floating pack ice would not significantly contribute to rising sea levels. Because they are lower in salinity, however, their melting would cause a very small increase in sea levels, so small that it is generally neglected.

Scientists previously lacked knowledge of changes in terrestrial storage of water. Surveying of water retention by soil absorption and by reservoirs outright ("impoundment") at just under the volume of Lake Superior agreed with a dam-building peak in the 1930s-1970s timespan. Such impoundment masked tens of millimetres of sea level rise in that span. ( B. F. Chao,* Y. H. Wu, Y. S. Li). If small glaciers and polar ice caps on the margins of Greenland and the Antarctic Peninsula melt, the projected rise in sea level will be around 0.5 m. Melting of the Greenland ice sheet would produce 7.2 m of sea-level rise, and melting of the Antarctic ice sheet would produce 61.1 m of sea level rise. The collapse of the grounded interior reservoir of the West Antarctic Ice Sheet would raise sea level by 5–6 m.

The snowline altitude is the altitude of the lowest elevation interval in which minimum annual snow cover exceeds 50%. This ranges from about 5,500 metres above sea-level at the equator down to sea level at about 70° N&S; latitude, depending on regional temperature amelioration effects. Permafrost then appears at sea level and extends deeper below sea level polewards.

As most of the Greenland and Antarctic ice sheets lie above the snowline and/or base of the permafrost zone, they cannot melt in a timeframe much less than several millennia; therefore it is likely that they will not, through melting, contribute significantly to sea level rise in the coming century. They can, however, do so through acceleration in flow and enhanced iceberg calving.

Climate changes during the 20th century are estimated from modelling studies to have led to contributions of between –0.2 and 0.0 mm/yr from Antarctica (the results of increasing precipitation) and 0.0 to 0.1 mm/yr from Greenland (from changes in both precipitation and runoff).

Estimates suggest that Greenland and Antarctica have contributed 0.0 to 0.5 mm/yr over the 20th century as a result of long-term adjustment to the end of the last ice age.

The current rise in sea level observed from tide gauges, of about 1.8 mm/yr, is within the estimate range from the combination of factors above but active research continues in this field. The terrestrial storage term, thought to be highly uncertain, is no longer positive, and shown to be quite large.

Geological influences

At times during Earth's long history, the configuration of the continents and seafloor have changed due to plate tectonics. This affects global sea level by determining the depths of the ocean basins and how glacial-interglacial cycles distribute ice across the Earth.

The depth of the ocean basins is a function of the age of oceanic lithosphere: as lithosphere becomes older, it becomes denser and sinks. Therefore, a configuration with many small oceanic plates that rapidly recycle lithosphere will produce shallower ocean basins and (all other things being equal) higher sea levels. A configuration with fewer plates and more cold, dense oceanic lithosphere, on the other hand, will result in deeper ocean basins and lower sea levels.

When there were large amounts of continental crust near the poles, the rock record shows unusually low sea levels during ice ages, because there was lots of polar land mass upon which snow and ice could accumulate. During times when the land masses clustered around the equator, ice ages had much less effect on sea level.

Over most of geologic time, long-term sea level has been higher than today (see graph above). Only at the Permian-Triassic boundary ~250 million years ago was long-term sea level lower than today. Long term changes in sea level are the result of changes in the oceanic crust, with a downward trend expected to continue in the very long term.

During the glacial/interglacial cycles over the past few million years, sea level has varied by somewhat more than a hundred metres. This is primarily due to the growth and decay of ice sheets (mostly in the northern hemisphere) with water evaporated from the sea.

The Mediterranean Basin's gradual growth as the Neotethys basin, begun in the Jurassic, did not suddenly affect ocean levels. While the Mediterranean was forming during the past 100 million years, the average ocean level was generally 200 metres above current levels. However, the largest known example of marine flooding was when the Atlantic breached the Strait of Gibraltar at the end of the Messinian Salinity Crisis about 5.2 million years ago. This restored Mediterranean sea levels at the sudden end of the period when that basin had dried up, apparently due to geologic forces in the area of the Strait.

Long-term causes			! Vertical effect
Change in volume of ocean basins
Plate tectonics and seafloor spreading (plate divergence/convergence) and change in seafloor elevation (mid-ocean volcanism)	Eustatic	0.01 mm/yr
Marine sedimentation	Eustatic
colspan="3" style="background:lightgray">Change in mass of ocean water
Melting or accumulation of continental ice	Eustatic	10 mm/yr
colspan="3"	• Climate changes during the 20th century
•• Antarctica (the results of increasing precipitation)	Eustatic
•• Greenland (from changes in both precipitation and runoff)	Eustatic
colspan="3"	• Long-term adjustment to the end of the last ice age
•• Greenland and Antarctica contribution over 20th century	Eustatic
Release of water from earth's interior	Eustatic
Release or accumulation of continental hydrologic reservoirs	Eustatic
colspan="3" style="background:lightgray"	Uplift or subsidence of Earth's surface (Isostasy)
Thermal-isostasy (temperature/density changes in earth's interior)	Local effect
Glacio-isostasy (loading or unloading of ice)	Local effect
Hydro-isostasy (loading or unloading of water)	Local effect
Volcano-isostasy (magmatic extrusions)	Local effect
Sediment-isostasy (deposition and erosion of sediments)	Local effect
colspan="3" style="background:lightgray"	Tectonic uplift/subsidence
Vertical and horizontal motions of crust (in response to fault motions)	Local effect	1–3 mm/yr
colspan="3" style="background:lightgray"	Sediment compaction
Sediment compression into denser matrix (particularly significant in and near river deltas)	Local effect
	Local effect
Earthquake-induced vibration	Local effect
colspan="3" style="background:lightgray"	Departure from geoid
Shifts in hydrosphere, aesthenosphere, core-mantle interface	Local effect
Shifts in earth's rotation, axis of spin, and precession of equinox	Eustatic
External gravity	gravitational changes	Eustatic
Evaporation and precipitation (if due to a long-term pattern)	Local effect

Changes through geologic time

Sea level has changed over geologic time. As the graph shows, sea level today is very near the lowest level ever attained (the lowest level occurred at the Permian-Triassic boundary about 250 million years ago).

During the most recent ice age (at its maximum about 20,000 years ago) the world's sea level was about 130 m lower than today, due to the large amount of sea water that had evaporated and been deposited as snow and ice, mostly in the Laurentide ice sheet. The majority of this had melted by about 10,000 years ago.

Hundreds of similar glacial cycles have occurred throughout the Earth's history. Geologists who study the positions of coastal sediment deposits through time have noted dozens of similar basinward shifts of shorelines associated with a later recovery. This results in sedimentary cycles which in some cases can be correlated around the world with great confidence. This relatively new branch of geological science linking eustatic sea level to sedimentary deposits is called sequence stratigraphy.

The most up-to-date chronology of sea level change during the Phanerozoic shows the following long term trends:

Gradually rising sea level through the Cambrian

Relatively stable sea level in the Ordovician, with a large drop associated with the end-Ordovician glaciation

Relative stability at the lower level during the Silurian

A gradual fall through the Devonian, continuing through the Mississippian to long-term low at the Mississippian/Pennsylvanian boundary

A gradual rise until the start of the Permian, followed by a gentle decrease lasting until the Mesozoic.

Recent changes

For at least the last 100 years, sea level has been rising at an average rate of about 1.8 mm per year. The majority of this rise can be attributed to the increase in temperature of the sea and the resulting thermal expansion of sea water. Additional contributions come from water sources on land such as melting snow and glaciers (see global warming).

Aviation

Using pressure to measure altitude results in two other types of altitude. Distance above ''true'' or ''MSL'' (mean sea level) is the next best measurement to absolute. MSL altitude is the distance above where sea level would be if there were no land. If one knows the elevation of terrain, the distance above the ground is calculated by a simple subtraction.

An MSL altitude—called pressure altitude by pilots—is useful for predicting physiological responses in unpressurized aircraft (see hypoxia). It also correlates with engine, propeller, and wing performance, which all decrease in thinner air.

Pilots can estimate height above terrain with an altimeter set to a defined barometric pressure. Generally, the pressure used to set the altimeter is the barometric pressure that would exist at MSL in the region being flown over. This pressure is referred to as either QNH or "altimeter" and is transmitted to the pilot by radio from air traffic control (ATC) or an Automatic Terminal Information Service (ATIS). Since the terrain elevation is also referenced to MSL, the pilot can estimate height above ground by subtracting the terrain altitude from the altimeter reading. Aviation charts are divided into boxes and the maximum terrain altitude from MSL in each box is clearly indicated. Once above the transition altitude (see below), the altimeter is set to the international standard atmosphere (ISA) pressure at MSL which is 1013.2 HPa or 29.92 inHg.

Flight level

MSL is useful for aircraft to avoid terrain, but at high enough altitudes, there is no terrain to avoid. Above that level, pilots are primarily interested in avoiding each other, so adjust their altimeter to standard temperature and pressure conditions (average sea level pressure and temperature) and disregard actual barometric pressure—until descending below transition level. To distinguish from MSL, such altitudes are called flight levels. Standard pilot shorthand is to express flight level as hundreds of feet, so FL 240 is . Pilots use the international standard pressure setting of 1013.25 hPa (29.92 inHg) when referring to Flight Levels. The altitude at which aircraft are mandated to set their altimeter to flight levels is called "transition altitude". It varies from country to country. For example in the U.S. it is 18,000 feet, in many European countries it is 3,000 or 5,000 feet.

See also

Above mean sea level

Flood myth

Geopotential height

List of places on land with elevations below sea level

Marine terrace

Normal height

''Normaal Amsterdams Peil''

''Normalhöhennull''

North West Shelf Operational Oceanographic System

Orthometric height

Sea level rise

Standard sea level

World Geodetic System

Meltwater pulse 1A

Notes

External links

Sea Level Rise:Understanding the past - Improving projections for the future

Permanent Service for Mean Sea Level

Global sea level change: Determination and interpretation

Environment Protection Agency Sea level rise reports

Properties of isostasy and eustasy

Measuring Sea Level from Space

Rising Tide Video: Scripps Institution of Oceanography

Sea Levels Online: National Ocean Service (CO-OPS)

Category:Oceanography Category:Cartography

ar:سطح البحر ast:Nivel de la mar az:Dəniz səviyyəsi bn:সমুদ্র সমতল map-bms:Nang dhuwur laut bg:Морско равнище ca:Nivell mitjà del mar cs:Hladina moře de:Meeresspiegel el:Μέση στάθμη θάλασσας es:Nivel del mar eo:Marnivelo eu:Itsas maila fa:سطح آب‌های آزاد fr:Niveau de la mer fur:Nivel dal mâr gl:Nivel medio do mar ko:해수면 hr:Razina mora id:Permukaan laut ia:Nivello del mar is:Sjávarmál it:Livello del mare he:גובה פני הים ka:ზღვის დონე sw:Usawa bahari wastani ku:Asta deryayê la:Maris aequor lv:Jūras līmenis ml:സമുദ്രനിരപ്പ് mr:समुद्रसपाटी ms:Aras laut nl:Zeeniveau ja:海面 no:Havnivå nn:Havnivå oc:Nivèl de la mar pl:Poziom morza pt:Nível médio do mar ru:Уровень моря simple:Sea level fi:Merenpinnan taso sv:Havsyta ta:கடல் மட்டம் te:సముద్రమట్టం th:ระดับน้ำทะเล uk:Рівень моря vi:Mực nước biển zh-classical:海平面 zh:海平面

name	Chuck Leavell
background	non_vocal_instrumentalist
birth name	Charles Alfred Leavell
born	April 28, 1952Birmingham, Alabama United States
instrument	Keyboards, Vocals, Piano
genre	Blues rock, Jazz rock, Jazz fusion, Southern rock
occupation	Musician, Songwriter
years active	1969–present
label	Capricorn Records
associated acts	The Allman Brothers BandThe Rolling StonesThe Black CrowesSea LevelEric ClaptonGov't Mule Aquarium Rescue Unit
website	ChuckLeavell.com
notable instruments	Hohner Clavinet }}

Chuck Leavell (born Charles Alfred Leavell, April 28, 1952) is an American pianist and keyboardist, who was a member of The Allman Brothers Band throughout the height of their popularity, a founding member of the jazz-rock combo Sea Level, a frequently-employed session musician, and later, the keyboardist for Eric Clapton and The Rolling Stones.

Biography

Born in Birmingham, Alabama, Leavell is a mostly self-taught musician. Inspired by seeing Ray Charles in concert (with Billy Preston in the backup band) to pursue a career in the industry, he dropped out of high school. Leavell made contacts with Macon, Georgia-based Capricorn Records, where he met his future wife, and relocated to Georgia.

Leavell joined the Allman Brothers in September 1972, when they decided not to recreate their dual lead guitar sound after the death of Duane Allman, who had died the previous October, but rather to use a different instrument as the second lead. Leavell's work was most prominent on the band's popular 1973 album ''Brothers and Sisters'', and in particular on the heavily-played instrumental "Jessica". However, only one studio album, 1975's ''Win, Lose or Draw'' followed, again with Leavell's ebullient piano and keyboard work featured, but with the band in chaos, and on the brink of destruction.

While opening shows for The Allman Brothers Band with The Allman Brothers' bass guitarist Lamar Williams and drummer Jaimoe, Leavell stepped up as a frontman for the first time in his career. After The Allman Brothers Band disbanding in May 1976, the trio added guitarist Jimmy Nalls and set about touring behind the moniker Sea Level, derived from Leavell's first initial and last name. The group lasted five years and released as many albums, each featuring a different configuration of the group.

After Sea Level disbanded, Leavell went to work as a studio musician, within a matter of months joining The Rolling Stones as second road keyboardist behind Ian Stewart for the band's 1982 European Tour. After Stewart's 1985 death, Leavell occupied the role of the group's road keyboardist by himself, frequently playing on studio recordings as well. He continues to go on tour with The Rolling Stones, as of 2006 as part of their record-grossing A Bigger Bang Tour. He served as the unofficial "musical director" for the band and devised each night's set list with Mick Jagger. "It's my job to keep Mick, Keith, Charlie and Ronnie all happy", Leavell says on his web page.

In addition to his work with The Rolling Stones, Leavell has worked with George Harrison, Eric Clapton, Gov't Mule, Train, The Black Crowes, Montgomery Gentry, amongst many others in the studio and on the road in addition to recording three solo albums.

In 2003, Leavell participated in the annual improvisional musical experiment known as Zambiland Orchestra in Atlanta.

Leavell was inducted into the Georgia Music Hall of Fame in 2004. He is also a member of the Alabama Music Hall of Fame. In an April 2007 radio interview on WOR-AM, Leavell said his three favorite contributions to songs in his career were "Jessica" with The Allman Brothers Band, "Old Love" on Eric Clapton's ''Unplugged'', and "Already Over Me" from the Rolling Stones' ''Bridges to Babylon'' record.

Leavell is a tree farmer in Twiggs County outside Macon, Georgia, an occupation that began when he inherited land in the early 1980s. Owner with his wife of Charlane Plantation, he is a two-time Georgia Tree Farmer of the Year, and is a staunch supporter of conservation and environmental protection. In 2006, Leavell wrote a children's book, ''The Tree Farmer''. In 2006 Leavell was appointed by Governor Sonny Perdue to the Georgia Land Conservation Council.

Leavell enjoys "giving back" to the community of his birth. In 1992, he played on a record titled "Mr. President", which was produced by noted Birmingham jazz keyboardist and vocalist Ray Reach for the purpose of raising money for the homeless in the Birmingham area. Leavell and several other well-known Alabama musicians (including Wayne Perkins, Chuck Tilley, Charlie Hayward, and Kelley O'Neal) donated their time for this worthy project.

On March 20, 2008, Leavell was given a BAMA Award (Birmingham Area Music Award) for his contributions to the Birmingham, Alabama musical heritage. The 2008 BAMA Awards ceremony was held at the Alabama Jazz Hall of Fame (in the historic Carver Theatre in the Birmingham Civil Rights District). Leavell performed at this ceremony, accompanied by the Alabama Jazz Hall of Fame All-Stars directed by Ray Reach. Also, at the same ceremony, a BAMA Award was bestowed upon keyboardist/producer Peter Wolf.

In April 2008, Leavell performed with a supergroup which opened for Chuck Berry in Boston. The concert raised money for artists struggling with addiction.

Leavell and Joel Babbit are the co-founders of The Mother Nature Network, an environmental news and information website that launched in January 2009. Leavell serves as director of environmental affairs and sits on the board of directors for the new company. He hosts two video series on mnn.com: "Love of the Land," in which he discusses sustainability and conservation issues, and "The Green Room," a series in which he interviews fellow celebrities about the environment and their philanthropic work.

Discography

Solo albums

(1998) ''What's in That Bag?''

(2001) ''Forever Blue: Solo Piano''

(2005) ''Southscape''

(2007) ''Live In Germany-Green Leaves and Blue Notes Tour''

With others

The Black Crowes

(1990) Shake Your Money Maker

Eric Clapton

(1992) Unplugged

Gov't Mule

(1998) Live ... With A Little Help From Our Friends

Alex Taylor

(1972) Dinnertime

The Allman Brothers Band

(1973) Brothers and Sisters

(1975) Win, Lose or Draw

Sea Level

(1977) ''Sea Level''

(1977) ''Cats on the Coast''

(1978) ''On the Edge''

(1979) ''Long Walk on a Short Pier''

(1980) ''Ball Room''

(1997) ''Best of Sea Level''

The Rolling Stones

(1983) ''Undercover''

(1986) ''Dirty Work''

(1989) ''Steel Wheels''

(1991) ''Flashpoint''

(1994) ''Voodoo Lounge''

(1995) ''Stripped''

(1998) ''No Security''

(2004) ''Live Licks''

(2005) ''A Bigger Bang''

(2008) ''Shine a Light''

Bibliography

Leavell, Chuck, with Mary Welch. ''Forever Green: The History and Hope of the American Forest''. Evergreen Arts, 2001. ISBN 0-86554-900-1.

Leavell, Chuck, with J. Marshall Craig. ''Between Rock and a Home Place''. Mercer University Press, 2004. ISBN 0-86554-975-3.

Leavell, Chuck. ''Chuck Leavell: Piano Instruction, Vol. 1'' (DVD) 2005.

Leavell, Chuck, Nicholas Cravotta, and Rebecca Bleau. ''The Tree Farmer''. VSP Books, 2005. ISBN 1-893622-16-9.

References

External links

Official website

New Georgia Encyclopedia entry

Leavell, Chuck. "Family Forestry in Twiggs County, Georgia / Live in Macon at the Douglass Theatre" ''Southern Spaces'' February 2006. http://southernspaces.org/2006/family-forestry-twiggs-county-georgia-live-macon-douglass-theatre

Interview and article focusing on Leavell's activism. "Chuck Leavell: Wrapped up in Trees" ''Crawdaddy!'' March 2008.

NPR interview, ''Marian McPartland's Piano Jazz'' 4-18-08

Mother Nature Network

}}

Category:1952 births Category:Living people Category:American rock keyboardists Category:American pianists Category:Musicians from Alabama Category:Musicians from Georgia (U.S. state) Category:American session musicians Category:The Allman Brothers Band members Category:American farmers Category:People from Birmingham, Alabama

da:Chuck Leavell nl:Chuck Leavell ja:チャック・リーヴェル

Randall Bramblett (b. Jesup, Georgia) is a musician and singer-songwriter, who has worked with such notable performers as Robbie Robertson, Elvin Bishop, Bonnie Bramlett, B.J. Thomas, Steve Winwood, Widespread Panic, Hydra, Sea Level, Gregg Allman and Roger Glover.

History

Randall Bramblett began recording in the 1970s. His first major touring band was Sea Level. Later in his career, he toured with Traffic, while continuing as a solo artist and studio musician.

In later years, Bramblett has been performing and touring with the Randall Bramblett Band. Their album ''Rich Someday'' was released in 2006.

Discography

Randall Bramblett/The Randall Bramblett Band

1975 ''That Other Mile''

1976 ''Light of the Night''

1998 ''See Through Me''

2001 ''No More Mr. Lucky''

2004 ''Thin Places''

2006 ''Rich Someday''

2008 ''Now It's Tomorrow''

2010 ''The Meantime''

Randall Bramblett Guest Appearances

1973 Gregg Allman, ''Laid Back'', Capricorn, Randall-sax

1973 Atlanta Rhythm Section, Decca, Randall-piano

1973 Cowboy, ''Boyer and Talton'', Capricorn, Randall-sax, vocals

1974 Elvin Bishop, ''Let it Flow'', Capricorn, Randall- sax

1974 Hydra, ''Hydra'', Capricorn, Randall-sax

1974 B.J Thomas, ''Longhorns & Londonbridges'', Paramount, Randall-piano, keys, vocals; several Randall songs on album.

1974 Gregg Allman, ''The Gregg Allman Tour'', Polygram, Randall-organ, horn,sax, horn arrangements

1975 Bonnie Bramlett, ''It's Time'', Capricorn, Randall-sax

1976 Bonnie Bramlett, ''Lady's Choice'', Capricorn, Randall-sax

1975 John Hammond, Jr., ''Can't Beat the Kid'', Capricorn, Randall-piano, keys

1977 Cowboy, ''Cowboy'', Capricorn, Randall-sax, vocals

1977 Allman and Woman, ''Two the Hard Way'', Capricorn, Randall-sax

1980 Robbie Robertson, ''Carny'' soundtrack, Warner Brothers, Randall-sax

1990 Steve Winwood, ''Refugees of the Heart'', Virgin, Randall-sax

1992 Elvin Bishop, ''Sure Feels Good: The Best of Elvin Bishop'', Polydor, Randall-sax

1993 Cowboy, ''A Different Time-The Best of Cowboy'', Polydor, Randall-sax

1994 Various Artists, ''Woodstock `94'' DVD, A&M;, Randall-woodwinds, keys

1994 Traffic, ''Traffic Live 1994'' DVD, Rhino, Randall-woodwinds, keys

1996 Jan Krist, ''Curious'', Silent Planet, Randall-piano, keys, sax

1996 Francine Reed, ''Can't Make it on my Own'', Ichiban, Randall-sax

1996 Johnny Jenkins, ''Blessed Blues'', Capricorn, Randall-organ, sax

1998 Vigilantes of Love, ''Live at the 40 Watt'', Paste, Randall-Hammond synth

1998 Allman Brothers Band, ''All Live'', Polygram International, Randall-sax

1998 Doubting Thomas, ''Who Died and Made You King?'', Oh Very, Randall-sax

1998 Filet of Soul, ''Incommunicado'', Shank, Randall-sax

2001 Vigilantes of Love, ''Summershine'', Compass, Randall-organ, piano, keys, mellotron,chamberlain

2001 Gov`t Mule, ''The Deep End, vol. 1'', ATO, Randall-organ

2001 Enlightenment Road Band, ''Songs from the Road to Enlightenment'',Five Feathers, Randall-piano, organ,sax, vocals

2001 Johnny Jenkins, ''Handle with Care'', Orchard, Randall-keys

2001 Jerry Joseph and the Jackmormons, ''Conscious Contact'', Terminus, Randall-organ, keys,Wurlitzer, vocals

2002 Widespread Panic, ''Live in the Classic City'', Sanctuary, Randall-sax

2002 Roger Glover, ''Snapshot'', Red Ink, Randall-piano, keys, organ, sax, vocals

2003 Deep Purple and Friends, ''Purple and Other Colours'', Snapper Music, Randall-vocal

2004 Widespread Panic, ''Jackassolantern'', Sanctuary, Randall-sax

2005 Traffic, ''Last Great Traffic Jam'', Legacy, Randall-woodwinds, keys

2005 Johnny Jenkins, ''All in Good Time'', Mean Old World, Randall-organ, keys,sax, vocals

2005 Chuck Leavell, ''Southscape'', Megaforce, Randall-recorder, sax

2008 Rick Fowler, ''Back on my Good Foot'', Jammates Records, Randall-organ

2008 Bonnie Bramlett, ''Beautiful'', Rockin` Camel, Randall-sax, keys, vocals

2008 Lingo, ''Through The Scattered Trees'', Randall-organ, sax

2011 Widesprad Panic, The Classic Center, Randall-sax

Official Websites

Randall Bramblett website

Randall Bramblett Band on Myspace

References

Allmusic

Reviews at The Music Box

Category:American musicians Category:New West Records artists Category:Musicians from Georgia (U.S. state) Category:Living people Category:People from Wayne County, Georgia

pl:Randall Bramblett

In aerodynamics, the sound barrier usually refers to the point at which an aircraft moves from transonic to supersonic speed. The term came into use during World War II when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their planes like an impediment to further acceleration. By the 1950s, new aircraft designs started to routinely "break" the sound barrier.

History

Some common whips such as the bullwhip or sparewhip are able to move faster than sound: the tip of the whip breaks the sound barrier and causes a sharp crack—literally a sonic boom. Firearms since the 19th century have generally had a supersonic muzzle velocity.

The sound barrier may have been first breached in nature some 150 million years ago. Some paleobiologists report that, based on computer models of their biomechanical capabilities, certain long-tailed dinosaurs such as apatosaurus and diplodocus may have possessed the ability to flick their tails at supersonic velocities, possibly used to generate an intimidating booming sound. This finding is theoretical and disputed by others in the field.

Early problems

The tip of the propeller on many early aircraft may reach supersonic speeds, producing a noticeable buzz that differentiates such aircraft. This is particularly noticeable on the Stearman, and noticeable on the T-6 Texan when it enters a sharp-breaking turn. This is undesirable, as the transonic air movement creates disruptive shock waves and turbulence. It is due to these effects that propellers are known to suffer from dramatically decreased performance as they approach the speed of sound. It is easy to demonstrate that the power needed to improve performance is so great that the weight of the required engine grows faster than the power output of the propeller. This problem was one of the issues that led to early research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany, who were led to their research specifically in order to avoid these problems in high-speed flight.

Propeller aircraft were, nevertheless, able to approach the speed of sound in a dive. This led to numerous crashes for a variety of reasons. These included the rapidly increasing forces on the various control surfaces, which led to the aircraft becoming difficult to control to the point where many suffered from powered flight into terrain when the pilot was unable to overcome the force on the control stick. The Mitsubishi Zero was infamous for this problem, and several attempts to fix it only made the problem worse. In the case of the Supermarine Spitfire, the wings suffered from low torsional stiffness, and when ailerons were moved the wing tended to flex such that they counteracted the control input, leading to a condition known as ''control reversal''. This was solved in later models with changes to the wing. The P-38 Lightning suffered from a particularly dangerous interaction of the airflow between the wings and tail surfaces in the dive that made it difficult to "pull out", a problem that was later solved with the addition of a "dive flap" that upset the airflow under these circumstances. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of de Havilland Swallow and death of its pilot, Geoffrey de Havilland, Jr.

All of these effects, although unrelated in most ways, led to the concept of a "barrier" that makes it difficult for an aircraft to break the speed of sound. .|group=N}}

Early claims

There are, however, several claims that the sound barrier was broken during World War II. Hans Guido Mutke claimed to have broken the sound barrier on 9 April 1945 in a Messerschmitt Me 262. Mutke reported not just transonic buffeting but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again. He also reported engine flame out. However, this claim is widely disputed by various experts believing the Me 262's structure could not support high transonic, let alone supersonic flight. The lack of area ruled fuselage and 10 percent thick wings did not prevent other aircraft from exceeding Mach 1 in dives. Chuck Yeager's Bell X-1, the North American F-86 Sabre (with Me-262 profile ) and the Convair Sea Dart seaplane exceeded Mach 1 without area rule fuselages. Computational tests carried out by Professor Otto Wagner of the Munich Technical University in 1999 suggest the Me 262 was capable of supersonic flight during steep dives. Recovering from the dive and the resumption of severe buffeting once subsonic flight was resumed would have been very likely to damage the craft terminally.

On page 13 of the "Me 262 A-1 Pilot's Handbook" issued by Headquarters Air Materiel Command, Wright Field, Dayton, Ohio as Report No. F-SU-1111-ND on January 10, 1946: The comments about restoration of flight control and cessation of buffeting above Mach 1 are very significant in a 1946 document.

In his book ''Me-163'', former Messerschmitt Me 163 "Komet" pilot Mano Ziegler claims that his friend, test pilot Heini Dittmar, broke the sound barrier when steep diving the rocket plane and that several people on the ground heard the sonic booms. Heini Dittmar had been accurately and officially recorded at 1,004.5 km/h (623.8 mph) in level flight on 2 October 1941 in the prototype Me 163 V4. He reached this speed at less than full throttle, as he was concerned by the transonic buffeting. The craft's Walter RII-203 cold rocket engine produced 7.34 kN (750 kgp / 1,650 lbf) thrust. The flight was made after a drop launch from a carrier plane to conserve fuel, a record that was kept secret until the war's end. The craft's potential performance in a powered dive is unknown, but the Me 163B test version of the series rocket plane had an even more powerful engine (HWK 109-509 A-2) and a greater wing sweep than the Me 163A. Ziegler claims that on 6 July 1944, Heini Dittmar, flying a test Me 163 B V18 VA + SP, was measured traveling at a speed of 1,130 km/h.

Similar claims for the Spitfire and other propeller aircraft are more suspect. It is now known that traditional airspeed gauges using a pitot tube give inaccurately high readings in the transonic regime, apparently due to shock waves interacting with the tube or the static source. This led to problems then known as "Mach jump

Attempts to break the sound barrier

The first powered flight faster than sound may have been the Soviet ramjet experiments of Yuri Pobedonostsev in 1933. Phosphorus-powered ramjets achieved speeds of 600–680 meters/second (Mach 2). Another early vehicle to break the sound barrier was probably the first successful test launch of the German V-2 ballistic missile on 3 October 1942, at Peenemünde in Germany. By September 1944, the V-2s routinely achieved Mach 4 (1,200 m/s) during terminal descent.

In 1942 the United Kingdom's Ministry of Aviation began a top secret project with Miles Aircraft to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype Miles M.52 jet aircraft, which was designed to reach 1,000 mph (417 m/s; 1,600 km/h) at 36,000 ft (11 km) in 1 minute 30 sec.

The aircraft's design introduced many innovations which are still used on today's supersonic aircraft. The single most important development was the all-moving tailplane, giving extra control to counteract the Mach tuck which allowed control to be maintained to and beyond supersonic speeds. This was wind-tunnel tested at Mach 0.86 in 1944 in the UK. In the immediate postwar era new data from captured German records suggested that major savings in drag could be had through a variety of means such as swept wings, and Director of Scientific Research, Sir Ben Lockspeiser, decided to cancel the project in light of this new information. Later experimentation with the Miles M.52 design proved that the aircraft would indeed have broken the sound barrier, with an unpiloted 3/10 scale replica of the M.52 achieving Mach 1.5 in October 1948. By that time, the sound barrier had been broken by the Americans, and also by the British De Havilland DH 108.

Sound barrier officially broken

U.S. efforts progressed apace soon after Britain had disclosed all its research and designs to the U.S. government on the promise that U.S. information would be shared the other way - a promise that the Americans did not keep. They utilized the information to initiate work on the Bell XS-1. The final version of the Bell XS-1 has many design similarities to the original Miles M.52 version. Also featuring the all-moving tail, the XS-1 was later known as the X-1. It was in the X-1 that Chuck Yeager was credited with being the first man to break the sound barrier in level flight on 14 October 1947, flying at an altitude of 45,000 ft (13.7 km). George Welch made a plausible but officially unverified claim to have broken the sound barrier on 1 October 1947, while flying an XP-86 Sabre. He also claimed to have repeated his supersonic flight on 14 October 1947, 30 minutes before Yeager broke the sound barrier in the Bell X-1. Although evidence from witnesses and instruments strongly imply that Welch achieved supersonic speed, the flights were not properly monitored and are not officially recognized. The XP-86 officially achieved supersonic speed on 26 April 1948.

On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened ''Glamorous Glennis''. The rocket-powered aircraft was launched from the bomb bay of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, at Mach 1.06 (361 m/s, 1,299 km/h, 807.2 mph) peak speed; however, Yeager and many other personnel believe Flight #49 (also with Yeager piloting), which reached a top recorded speed of Mach 0.997 (339 m/s, 1,221 km/h), may have, in fact, exceeded Mach 1. (The measurements were not accurate to three significant figures and no sonic boom was recorded for that flight.)

As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1948 Collier Trophy to be shared by the three main participants in the program. Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the NACA contributions.

Jackie Cochran was the first woman to break the sound barrier on May 18, 1953, in a Canadair Sabre, with Yeager as her wingman.

The sound barrier fades

As the science of high-speed flight became more widely understood, a number of changes led to the eventual disappearance of the "sound barrier". Among these were the introduction of swept wings, the area rule, and engines of ever-increasing performance. By the 1950s many combat aircraft could routinely break the sound barrier in level flight, although they often suffered from control problems when doing so, such as Mach tuck. Modern aircraft can transit the "barrier" without it even being noticeable.

By the late 1950s the issue was so well understood that many companies started investing in the development of supersonic airliners, or SSTs, believing that to be the next "natural" step in airliner evolution. History has proven this not to be the case, at least yet, but Concorde and the Tupolev Tu-144 both entered service in the 1970s regardless.

Although Concorde and the Tu-144 were the first aircraft to carry commercial passengers at supersonic speeds, they were not the first or only commercial airliners to break the sound barrier. On 21 August 1961, a Douglas DC-8 broke the sound barrier at Mach 1.012 or 1,240 km/h (776.2 mph) while in a controlled dive through 41,088 feet (12,510 m). The purpose of the flight was to collect data on a new leading-edge design for the wing. A China Airlines 747 may have broken the sound barrier in an unplanned descent from 41,000 ft (12,500 m) to 9,500 ft (2,900 m) after an in-flight upset on 19 February 1985. It also reached over 5g.

Breaking the sound barrier in a land vehicle

On 15 October 1997, in a vehicle designed and built by a team led by Richard Noble, British driver (and Royal Air Force pilot) Andy Green became the first person to break the sound barrier in a land vehicle in compliance with Fédération Internationale de l'Automobile rules. The vehicle, called the ThrustSSC ("Super Sonic Car"), captured the record exactly 50 years and one day after Yeager's flight.

References

;Notes ;Citations ;Bibliography

"Breaking the Sound Barrier." ''Modern Marvels (TV program)''. July 16, 2003.

Brown, Eric. "Miles M.52: The Supersonic Dream." ''Air Enthusiast Thirteen'', August–November 1980. ISSN 01443-5450.

Hallion, Dr. Richard P. "Saga of the Rocket Ships." ''AirEnthusiast Five'', November 1977-February 1978. Bromley, Kent, UK: Pilot Press Ltd., 1977.

Käsmann, Ferdinand C.W. ''Die schnellsten Jets der Welt'' (in German). Berlin: Aviatic-Verlag GmbH, 1999. ISBN 3-925505-26-1.

Miller, Jay. ''The X-Planes: X-1 to X-45,'' Hinckley, UK: Midland, 2001. ISBN 1-85780-109-1.

Pisano, Dominick A., R. Robert van der Linden and Frank H. Winter. ''Chuck Yeager and the Bell X-1: Breaking the Sound Barrier''. Washington, DC: Smithsonian National Air and Space Museum (in association with Abrams, New York), 2006. ISBN 0-8109-5535-0.

Portway, Donald. ''Military Science Today''. London: Oxford University Press, 1940.

Radinger, Willy and Walter Schick. ''Me 262'' (in German). Berlin: Avantic Verlag GmbH, 1996. ISBN 3-925505-21-0.

Wagner, Ray. ''The North American Sabre''. London: Macdonald, 1963.

Winchester, Jim. "Bell X-1." ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft'' (The Aviation Factfile). Kent, UK: Grange Books plc, 2005. ISBN 1-84013-309-2.

Wolfe. Tom. ''The Right Stuff''. New York: Farrar, Straus and Giroux, 1979. ISBN 0-374-25033-2.

Yeager, Chuck, Bob Cardenas, Bob Hoover, Jack Russell and James Young. ''The Quest for Mach One: A First-Person Account of Breaking the Sound Barrier''. New York: Penguin Studio, 1997. ISBN 0-670-87460-4.

Yeager, Chuck and Leo Janos. ''Yeager: An Autobiography''. New York: Bantam, 1986. ISBN 0-553-25674-2.

External links

Fluid Mechanics, a collection of tutorials by Dr. Mark S. Cramer, Ph.D

''Breaking the Sound Barrier with an Aircraft'' by Carl Rod Nave, Ph.D

a video of a Concorde reaching Mach 1 at intersection TESGO taken from below

An interactive Java applet, illustrating the sound barrier.

Category:Aviation terminology Category:Airspeed

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