The International Association of Geodesy (IAG) and the International Astronomical Union (IAU) have chosen to use an equatorial radius of (codified as the IAU 2009 value). This equatorial radius is also in the 2003 and 2010 IERS Conventions. It is also the equatorial radius used for the IERS 2003 ellipsoid. If it were really circular, the length of the equator would then be exactly 2π times the radius, namely . The GRS 80 (Geodetic Reference System 1980) as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of . The WGS 84 (World Geodetic System 1984) which is a standard for use in cartography, geodesy, and satellite navigation including GPS, also has an equatorial radius of .
Exact length
Equator
Equator | Exact length
The equator is 0.16% longer than a meridian. Sorry. I cannot find the answer based on the context. Sorry. I cannot find the answer based on the context. Sorry. I cannot find the answer based on the context.
what are the major global wind systems on earth
user
polar easterlies, westerlies to name a few.
assistant
what is the first one about?
user
are the dry, cold prevailing winds that blow from the high-pressure areas towards the low-pressure areas.
assistant
how does it effect the precipitation?
user
Orographic precipitation occurs on the windward side of mountains and is caused by the rising air motion of a large-scale flow of moist air across the mountain ridge, resulting in adiabatic cooling and condensation.
assistant
are there any trade that depend on this?
user
Yes, The trade winds.
assistant
what does it mean?
user
They are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator.
assistant
what is the length of the last thing mentioned?
user
Easterly winds, on average, dominate the flow pattern across the poles, westerly winds blow across the mid-latitudes of the earth, polewards of the subtropical ridge, while easterlies again dominate the tropics. Directly under the subtropical ridge are the doldrums, or horse latitudes, where winds are lighter. Many of the Earth's deserts lie near the average latitude of the subtropical ridge, where descent reduces the relative humidity of the air mass. The strongest winds are in the mid-latitudes where cold polar air meets warm air from the tropics.
Wind | Global climatology
These strong winds bring cooler sub-surface waters to the surface of the tropical eastern Pacific Ocean and may last from a few hours to 6 days.
Tehuantepecer | Introduction
At the Equator, the daytime period always lasts about 12 hours, regardless of season. As viewed from the Equator, the Sun always rises and sets vertically, following an apparent path nearly perpendicular to the horizon. Due to the axial tilt of Earth, Sun always lies within 23.44° north or south of the celestial equator, so the subsolar point always lies within the tropics. From the March equinox to the September equinox, the Sun rises within 23.44° north of due east, and sets within 23.44° north of due west. From the September equinox to the March equinox, the Sun rises within 23.44° south of due east and sets within 23.44° south of due west.
Daytime | At the Equator
For both GRS 80 and WGS 84, this results in a length for the equator of . The geographical mile is defined as one arc-minute of the equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is , while by IAU-2000, it is . This is a difference of less than over the total distance (approximately ). The earth is commonly modeled as a sphere flattened 0.336% along its axis. This makes the equator 0.16% longer than a meridian (a great circle passing through the two poles). The IUGG standard meridian is, to the nearest millimetre, , one arc-minute of which is , explaining the SI standardization of the nautical mile as , more than less than the geographical mile.
Equator | Exact length
The zonal wind of this component has the amplitude "u" at the equator relative to the ground, where "u" > 0 indicates superrotation and "u" < 0 indicates retrograde rotation with respect to the solid Earth. All other wind terms merely redistribute the AAM with latitude, an effect that cancels out when averaged over the globe.
Day length fluctuations | Exchange of angular momentum
The "thermal wind equation" is where the are geopotential height fields with , is the Coriolis parameter, and is the upward-pointing unit vector in the vertical direction. The thermal wind equation does not determine the wind in the tropics. Since is small or zero, such as near the equator, the equation reduces to stating that is small.
Wind shear | Thermal wind
Storms can last for days at a time.) These conditions continue through polar sunrise, but reverse dramatically with the onset of freshet, which brings high, gusting winds.
Dr. Neil Trivett Global Atmosphere Watch Observatory | Climate
Its poleward progression is accelerated by the development of a heat low over the Asian, African, and North American continents during May through July, and over Australia in December.
Wind | Tropics
The period of twilight is shortest at the Equator, where the equinox Sun rises due east and sets due west, at a right angle to the horizon. Each stage of twilight (civil, nautical, and astronomical) lasts only 24 minutes. From anywhere on Earth, the twilight period is shortest around the equinoxes and longest on the solstices.
Dawn | Equator
This contrasts with the small (1%) increase in the length of a degree of latitude (north-south distance), equator to pole. The table shows both for the WGS84 ellipsoid with = and = . Note that the distance between two points 1 degree apart on the same circle of latitude, measured along that circle of latitude, is slightly more than the shortest (geodesic) distance between those points (unless on the equator, where these are equal); the difference is less than .
Longitude | Length of a degree of longitude
The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics towards the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over the world's oceans. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean, as well as portions of southeast North America. A monsoon is a seasonal prevailing wind that lasts for several months within tropical regions. The term was first used in English in India, Bangladesh, Pakistan, and neighboring countries to refer to the big seasonal winds blowing from the Indian Ocean and Arabian Sea in the southwest bringing heavy rainfall to the area.
Wind | Tropics
The longitudinal extent of cut locus is approximately . If is exact and as a consequence the equator is only a shortest geodesic if . For a prolate ellipsoid, the cut locus is a segment of the anti-meridian centered on the point antipodal to , , and this means that meridional geodesics stop being shortest paths before the antipodal point is reached.
Geodesics on an ellipsoid | Behavior of geodesics
For the other half of the orbit, the South Pole is tilted slightly toward the Sun, and it is winter in the Northern Hemisphere. This means that at the equator, the Sun is not directly overhead at noon, except around the March and September equinoxes, when one spot on the equator is pointed directly at the Sun.
Spherical Earth | Changing length of the day
Now find the point N on the equator which is such that the number of equatorial degrees in ON is numerically equal to the latitude difference (45° for AM on the unequal scale). Draw the perpendicular through N and let it meet OQ at D. Find the point E such that OE=OD, here approximately 54°. This is a measure of the rhumb line distance between the points on the sphere corresponding to A and B on the spherical Earth. Since each degree on the equator corresponds to 60 nautical miles the sailing distance is 3,240 nautical miles for this example.
Mercator 1569 world map | Distances and the Organum Directorium
The low-level surface trade winds, which normally blow from east to west along the equator, either weaken or start blowing from the other direction.
Tropic of Capricorn | Australia
At a few degrees north of the equator the perihelion/aphelion factor is balanced by the fact that the angle of the Sun is slightly more direct, and the days are slightly longer, at the time of the summer solstice for the Northern Hemisphere (most commonly on June 21), making the level of insolation virtually the same in both "summer" and "winter."
Thermal equator | Introduction
It is allowed to have one single waypoint to lengthen the calculated track. The equator must be crossed.
Circumnavigation | Wind powered
Because of elliptic nature of the Earth's orbit, the Southern Hemisphere is not symmetrical: the Antarctic Circle, with 4,530 hours of daylight, receives five days less of sunshine than its antipodes. The Equator has a total daytime of 4,422 hours per year.
Sunshine duration | Daytime duration
The length of the day varies because as the Earth rotates some places (near the poles) pass through only a short curve near the top or bottom of the sunlight half; other places (near the equator) travel along much longer curves through the middle.
Spherical Earth | Length of the day beyond <a href="polar%20circle">polar circle</a>s
The data in "The Winds of the Globe" leads to conclusions that generally agree with those of its predecessor. Woeikof confirms the existence of the two Trade Winds found above 30° latitude, and established the existence of a third, southwesterly band between 0°-30° latitude. The greater wealth of data also allows Woeikof to give a more accurately describe the extent of these winds, each of the three spanning 30° latitude from the equator on top of the other. Another novel contribution was the realization that these wind bands shift with the seasons. When the sun is in its zenith over the northern hemisphere (our summer) the equatorial band moves northward, as do all the others.
James Henry Coffin | "Analysis"
In the tropical atmosphere, the order of magnitude of the pressure deviations is so small that the contribution of the Eötvös effect to the pressure deviations is considerable. In addition, objects travelling upwards ("i.e.", out) or downwards ("i.e.", in) are deflected to the west or east respectively. This effect is also the greatest near the equator. Since vertical movement is usually of limited extent and duration, the size of the effect is smaller and requires precise instruments to detect. For example, idealized numerical modeling studies suggest that this effect can directly affect tropical large-scale wind field by roughly 10% given long-duration (2 weeks or more) heating or cooling in the atmosphere.
Coriolis force | Eötvös effect
The equator of the sphere is a parametrized curve given by with ranging from 0 to 2. The line element may be used to calculate the length of this curve.
First fundamental form | Length of a curve on the sphere
If midwinter sunrise and set are at 09:00 and 15:00, and midsummer at 03:00 and 21:00, the daylight duration will shift by 0:30, 1:00, 1:30, 1:30, 1:00 and 00:30 over the six months from one solstice to the other. Likewise the day length changes by 0:30, 1:00, 1:30, 1:30, 1:00 and 00:30 each month. More equatorial latitudes change by less, but still in the same proportions; more polar by more.
Rule of twelfths | Daylength
This region is known as the Intertropical Convergence Zone. This zone is the result of trade winds from the northern and southern part of the hemisphere eventually joining together. Still another definition states that the thermal equator is the latitude at which insolation is identical throughout the year. This is not the same as the astronomical equator because the Earth reaches perihelion (the minimum distance from the Sun in its orbit) in early January and is at aphelion (maximum distance) in early July. Therefore, insolation is somewhat higher at 0° latitude in January than in July even though the height of the Sun (at noon) and the length of day (from sunrise to sunset) is essentially the same.
Thermal equator | Introduction
To a person on Earth, the Sun appears to travel above the equator (or along the celestial equator) at these times. Light rays from the Sun's center are perpendicular to Earth's surface at the point of solar noon on the equator. Locations on the equator experience the shortest sunrises and sunsets because the Sun's daily path is nearly perpendicular to the horizon for most of the year. The length of daylight (sunrise to sunset) is almost constant throughout the year; it is about 14 minutes longer than nighttime due to atmospheric refraction and the fact that sunrise begins (or sunset ends) as the upper limb, not the center, of the Sun's disk contacts the horizon.
Equator | Overview
However, this relationship is indirect via the large-scale dynamics of the tropics; the direct influence of the absolute sea surface temperature on formula_7 is weak in comparison.
Tropical cyclone | Characteristic values and variability on Earth
Wind speeds increase with the distance from the equator, reaching zero values near ±20° latitude, where the troposphere's temperature minimum is located. Closer to the poles, the winds shift to a prograde direction, flowing with Uranus's rotation. Wind speeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles. Wind speeds at −40° latitude range from . Because the collar obscures all clouds below that parallel, speeds between it and the southern pole are impossible to measure. In contrast, in the northern hemisphere maximum speeds as high as are observed near +50° latitude.
Uranus | Banded structure, winds and clouds
The length of a degree of longitude (east-west distance) depends only on the radius of a circle of latitude. For a sphere of radius that radius at latitude is , and the length of a one-degree (or radian) arc along a circle of latitude is When the Earth is modelled by an ellipsoid this arc length becomes where , the eccentricity of the ellipsoid, is related to the major and minor axes (the equatorial and polar radii respectively) by An alternative formula is Cos decreases from 1 at the equator to 0 at the poles, which measures how circles of latitude shrink from the equator to a point at the pole, so the length of a degree of longitude decreases likewise.
Longitude | Length of a degree of longitude
The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator, equatorward of the subtropical ridge. These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over world's oceans, guiding their path westward. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean sea, as well as portions of southeast North America.
Prevailing winds | Trades and their impact
Hot air rises at the Equator and is pushed towards the poles by cooler air travelling towards the Equator (an atmospheric circulation feature known as the Hadley Cell). At about 30 degrees from the equator, the outward-travelling air sinks to lower altitudes, and continues toward the poles closer to the ground (the Ferrel Cell), then rises up again from about 60 degrees as the air joins the Polar vortex. This travel in the 30 to 60 degree zone combines with the rotation of the earth to move the air currents from west to east, creating westerly winds. Unlike in the northern hemisphere, the large tracts of open ocean south of the 40th parallel south (interrupted only by Tasmania, New Zealand, and the southern part of South America) allow higher windspeeds to develop.
Roaring Forties | Mechanics
Planes parallel to the equatorial plane intersect the surface in circles of constant latitude; these are the parallels. The Equator has a latitude of 0°, the North Pole has a latitude of 90° North (written 90° N or +90°), and the South Pole has a latitude of 90° South (written 90° S or −90°). The latitude of an arbitrary point is the angle between the equatorial plane and the normal to the surface at that point: the normal to the surface of the sphere is along the radius vector. The latitude, as defined in this way for the sphere, is often termed the spherical latitude, to avoid ambiguity with the geodetic latitude and the auxiliary latitudes defined in subsequent sections of this article.
Latitude | The graticule on the sphere
In Meridian arc and standard texts it is shown that the distance along a meridian from latitude to the equator is given by ( in radians) where is the meridional radius of curvature. The distance from the equator to the pole is
Latitude | Length of a degree of latitude
Earth's Equator, spelled with capital E, is a specific case of a planetary equator. It is about long, of which 78.8% lies across water and 21.3% over land. In spatial (3D) geometry, as applied in astronomy, the equator of a rotating spheroid (such as a planet) is the parallel (circle of latitude) at which latitude is defined to be 0°. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles.
Equator | Introduction
For instance, the thermal wind associated with pole-to-equator temperature gradients is the primary physical explanation for the jet stream in the upper half of the troposphere, which is the atmospheric layer extending from the surface of the planet up to altitudes of about 12-15 km. Mathematically, the thermal wind relation defines a vertical wind shear – a variation in wind speed or direction with height. The wind shear in this case is a function of a horizontal temperature gradient, which is a variation in temperature over some horizontal distance. Also called baroclinic flow, the thermal wind varies with height in proportion to the horizontal temperature gradient.
Thermal wind | Introduction
Seasons result from the tilt of the Earth's axis compared to the plane of its revolution around the Sun. Throughout the year the northern and southern hemispheres are alternately turned either toward or away from the sun depending on Earth's position in its orbit. The hemisphere turned toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter (see solstice). At the equinoxes, the Earth's axis is perpendicular to the sun rather than tilted toward or away, meaning that day and night are both about 12 hours long across the whole of the Earth.
Equator | Equatorial seasons and climate
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and midway between the poles. On Earth, "the Equator", at 0° latitude, divides the Northern and Southern Hemispheres. Equator may also refer to:
Equator (disambiguation) | Introduction
The equator is the circle that is equidistant from the North Pole and South Pole. It divides the Earth into the Northern Hemisphere and the Southern Hemisphere. Of the parallels or circles of latitude, it is the longest, and the only 'great circle' (a circle on the surface of the Earth, centered on Earth's center). All the other parallels are smaller and centered only on Earth's axis.
Circle of latitude | Equator
The Sun's path lies entirely in the northern half of the celestial sphere from the March equinox to the September equinox, but lies entirely in the southern half of the celestial sphere from the September equinox to the March equinox. On the equinoxes, the equatorial Sun culminates at the zenith, passing directly overhead at solar noon. The fact that the equatorial Sun is always so close to the zenith at solar noon explains why the tropical zone contains the warmest regions on the planet overall. Additionally, the Equator sees the shortest sunrise or sunset because the Sun's path across the sky is so nearly perpendicular to the horizon.
Daytime | At the Equator
Using the larger Pacific basin as an example, the resulting dynamic height pattern consists of a trough at the equator, and ridge near 5° degrees north, a trough at 10°N, and finally a ridge closer to 20°N. From geostrophy (the perfect balance between the mass field and velocity field), the NECC is located between the ridge and trough at 5°N and 10°N, respectively. Sverdrup theory succinctly summarizes this phenomenon mathematically by defining a geostrophic mass transport per unit latitude, M, as the east-west integral of the meridional derivative of wind stress curl, minus any Ekman transport. The Ekman transport into the current is typically negligible, at least in the Pacific NECC.
Equatorial Counter Current | Theoretical Background
At this latitude the nighttime duration lasts 9 hours, 55 minutes during the summer solstice and 13 hours, 47 minutes during the winter solstice. On 21 June, the maximum altitude of the sun is 83.44 degrees and 36.56 degrees on 21 December.
30th parallel north | Introduction
From March to April, during which the temperature of the equator reaches maximum, winds are weakest and the sun shines directly over the equator. So, SST is uniformly warm near the equator, which makes the ITCZ really sensitive to even small disturbance of SST and explains the relaxation of cross-equator winds in spring. From July to September, during which the temperature of the equator reaches its minimum, ITCZ reaches its northernmost location, which explains the intensification of cross-equator winds. It can be seen that the process of cooling takes 3 months while that of warming takes 7 months, which are asymmetric.
Tropical Atlantic Variability | Annual Cycle
Heating of the earth near the equator leads to large amounts of convection along the monsoon trough or Intertropical convergence zone. This air mass rises to the lower stratosphere where it diverges, moving away from the equator in the upper troposphere in both northerly and southerly directions. As it moves towards the mid-latitudes on both sides of the equator, the air cools and sinks. The resulting air mass subsidence creates a subtropical ridge of high pressure near the 30th parallel in both hemispheres. At the surface level, the sinking air diverges again with some returning to the equator, completing the Hadley circulation.
Horse latitudes | Formation
The atmospheric circulation pattern that George Hadley described was an attempt to explain the trade winds. The Hadley cell is a closed circulation loop which begins at the equator. There, moist air is warmed by the Earth's surface, decreases in density and rises. A similar air mass rising on the other side of the equator forces those rising air masses to move poleward. The rising air creates a low pressure zone near the equator. As the air moves poleward, it cools, becomes denser, and descends at about the 30th parallel, creating a high-pressure area. The descended air then travels toward the equator along the surface, replacing the air that rose from the equatorial zone, closing the loop of the Hadley cell.
Atmospheric circulation | Hadley cell
That would give approximate dimensions of 940 × 766 × 490 km, with its longest axis nearly twice as long as its polar axis.
(208996) 2003 AZ84 | Physical characteristics
The high angles (around the zenith) of the Sun causes the tropics to be warm, while low angles (barely above the horizon) causes the polar regions to be cold. The slight effect of daylight hours on average seasonal temperature can be seen with the poles and tropical regions. The poles are still cold during their respective summers, despite seeing 24 hours of daylight for six months, while the Equator remains warm throughout the year, with only 12 hours of daylight per day. Although the daytime length at the Equator remains 12 hours in all seasons, the duration at all other latitudes varies with the seasons.
Daytime | Daytime variations with latitude and seasons
The term tropic refers to the tropics, a region of the Earth surrounding the Equator. Tropic or Tropics may also refer to:
Tropic (disambiguation) | Introduction
Nevertheless, temperatures are high year round due to the earth's axial tilt of 23.5° not being enough to create a low minimum midday declination to sufficiently weaken the sun's rays even during the solstices.
Equator | Equatorial seasons and climate
The shape of the Earth closely resembles a flattened sphere (a spheroid) with equatorial radius formula_17 of 6378.137 km; distance formula_18 from the center of the spheroid to each pole is 6356.7523142 km. When calculating the length of a short north-south line at the equator, the circle that best approximates that line has a radius of formula_19 (which equals the meridian's semi-latus rectum), or 6335.439 km, while the spheroid at the poles is best approximated by a sphere of radius formula_20, or 6399.594 km, a 1% difference. So long as a spherical Earth is assumed, any single formula for distance on the Earth is only guaranteed correct within 0.5% (though better accuracy is possible if the formula is only intended to apply to a limited area).
Great-circle distance | Radius for spherical Earth
The maximum sustained wind normally occurs at a distance from the center known as the radius of maximum wind, within a mature tropical cyclone's eyewall, before winds decrease at farther distances away from a tropical cyclone's center. Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organization (WMO), which specifies measuring winds at a height of for 10 minutes, and then taking the average. However, the United States National Weather Service defines sustained winds within tropical cyclones by averaging winds over a period of one minute, measured at the same height. This is an important distinctions, as the value of the highest one-minute sustained wind is about 14% greater than a ten-minute sustained wind over the same period.
Maximum sustained wind | Definition
As part of the Hadley model of atmospheric circulation, the equator is characterised by the ascending branches of separate meridional cells, driven by intense insolation. The vertical convection draws in air from the surrounding atmosphere, known as the trade winds. As these inwards flows of air converge they reduce horizontal wind speed, and as they rise, they form precipitation. The vertical convection also results in a net export of heat and freshwater from the lower atmosphere into the troposphere This system is known as the ITCZ. The location of the ITCZ is centred on the areas of highest insolation, although it is more stationary over the oceans than landmasses.
Geography of South America | Climate
The current's core coincides with the thermocline and its distance from the parallel Equatorial Counter Current is approximately 300 km. It has 1000 times the volume of Mississippi River and its length is 3500 miles (6000 km).
Cromwell Current | Introduction
Loess, or windblown dust, can be employed as an indicator of past atmospheric circulation patterns. Without the presence of the monsoon, surface winds across the globe would have been primarily zonal and easterly. However, the geologic record not only indicates that winds exhibited a meridional, cross-equatorial pattern, but also that western Pangea experienced westerly flow during the peak period of the megamonsoon.
Pangean megamonsoon | Loess
As such, the current tends to reverse hemispheres seasonally in that basin. The NECC has a pronounced seasonal cycle in the Atlantic and Pacific, reaching maximum strength in late boreal summer and fall and minimum strength in late boreal winter and spring. Furthermore, the NECC in the Atlantic disappears in late winter and early spring. The NECC is an interesting case because while it results from wind-driven circulation, it transports water against the mean westward wind stress in the tropics. This apparent paradox is concisely explained by Sverdrup theory, which shows that the east-west transport is governed by the north-south change in the curl of the wind stress.
Equatorial Counter Current | Introduction
As part of the Hadley cell, 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, near-equatorial trough, intertropical front, or the Intertropical Convergence Zone. When located within a monsoon region, this zone of low pressure and wind convergence is also known as the monsoon trough. 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 moisture content remains constant, which lowers the relative humidity of the air mass.
Trade winds | Cause
The International Association of Geodesy (IAG) and the International Astronomical Union (IAU) have chosen to use an equatorial radius of (codified as the IAU 2009 value). This equatorial radius is also in the 2003 and 2010 IERS Conventions. It is also the equatorial radius used for the IERS 2003 ellipsoid. If it were really circular, the length of the equator would then be exactly 2π times the radius, namely . The GRS 80 (Geodetic Reference System 1980) as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of . The WGS 84 (World Geodetic System 1984) which is a standard for use in cartography, geodesy, and satellite navigation including GPS, also has an equatorial radius of .
Equator | Exact length
A strict meteorological definition of a terrestrial storm is a wind measuring 10 or higher on the Beaufort scale, meaning a wind speed of 24.5 m/s (89 km/h, 55 mph) or more; however, popular usage is not so restrictive. Storms can last anywhere from 12 to 200 hours, depending on season and geography. In North America, the east and northeast storms are noted for the most frequent repeatability and duration, especially during the cold period. Big terrestrial storms alter the oceanographic conditions that in turn may affect food abundance and distribution: strong currents, strong tides, increased siltation, change in water temperatures, overturn in the water column, etc.
Storm | Classification
The length of these seasons is not uniform because of Earth's elliptical orbit and its different speeds along that orbit.
Season | Mid-latitude thermal lag
Continuing south from the equator, though Polaris is no longer visible, Crux ("Luubw"), the "Southern Cross", will have risen above the southern horizon. Travelling further southward, Crux rises higher in the sky. Through Crux's longest axis, an imaginary line bisecting Gacrux and Acrux points southward toward the . However, the South Pole has no true zenith star from which direct readings of south latitude may be taken. As a proxy, the southern celestial pole lies at the end of that imaginary line extended southward through Gacrux and Acrux, at a distance about 4.5 times the distance between them. Nainoa Thompson notes that at Hawaii's latitude, the distance between Gacrux and the southerly Acrux is equal to Acrux's altitude above the southern horizon.
Mau Piailug | Technique
The precise location of the equator is not truly fixed; the true equatorial plane is perpendicular to the Earth's rotation axis, which drifts about during a year. This effect must be accounted for in detailed geophysical measurements. Geological samples show the equator significantly changed positions between 12 and 48 million years ago, as sediment deposited by ocean thermal currents at the equator have shifted. The deposits by thermal currents are determined by the axis of the earth, which determines solar coverage of the Earth's surface. Changes in Earth axis can also be observed in the geographic layout of volcanic island chains, which are created by shifting hot spots under the Earth's crust as the axis and crust move.
Equator | Precise location
Along the equator, consecutive swaths are separated by 2,800 km. QuikSCAT orbits Earth at an altitude of 802 km and at a speed of about 7 km per second.
QuikSCAT | Instrument description
In the year 2000 AD the mean value of the tilt was about 23° 26′ 21″. The main long-term cycle causes the axial tilt to fluctuate between about 22.1° and 24.5° with a period of 41,000 years. Currently, the "average" value of the tilt is decreasing by about 0.47″ per year. As a result, (approximately, and on average) the Tropical Circles are drifting towards the equator (and the Polar Circles towards the poles) by 15 metres per year, and the area of the Tropics is decreasing by per year.
Circle of latitude | Movement of the Tropical and Polar Circles
Length of day increases from the equator towards the South Pole in the Southern Hemisphere in December (around the summer solstice there), but decreases towards the North Pole in the Northern Hemisphere at the time of the northern winter solstice.
Winter solstice | Length of the day near the northern winter solstice
osbornianus", 55.6 mya) and after ("E. osbornianus", 55.3 mya) the brief climatic peak period.
Ectocion | Introduction
There are regular patterns of prevailing winds found in bands round the Earth's equatorial region. The zone designated the trade winds is the zone between about 30° N and 30° S, blowing predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The westerlies are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. The strongest westerly winds in the middle latitudes can come in the Roaring Forties between 30 and 50 degrees latitude.
Rain shadow | Regions of notable rain shadow
Around the poles, which coincide with the rotational axis of Earth as it passes through the surface, the seasonal variations in the length of daytime are extreme. In fact, within 23.44° latitude of the poles, there will be at least some days each year during which the sun never goes below the horizon. There will also be days when the Sun never rises above the horizon. This number will be fewer, but close to the number of days in the summer where the sun doesn't set (for example the sunrise is usually a few days before the spring equinox and extends a few days past the fall equinox).
Daytime | Around the poles
Trade winds in tropical regions near the equator can also shape trees in a similar manner.
Krummholz | Flag tree
The remainder of this article discusses the relationship between the period of these waves, their wavelength in the zonal (east-west) direction and their speeds for a simplified ocean.
Equatorial wave | Introduction
On the GRS80 or WGS84 spheroid at sea level at the Equator, one latitudinal second measures 30.715 meters, one latitudinal minute is 1843 meters and one latitudinal degree is 110.6 kilometers. The circles of longitude, meridians, meet at the geographical poles, with the west–east width of a second naturally decreasing as latitude increases. On the Equator at sea level, one longitudinal second measures 30.92 meters, a longitudinal minute is 1855 meters and a longitudinal degree is "111.3 kilometers. At 30° a longitudinal second is 26.76 meters, at Greenwich (51°28′38″N) 19.22 meters, and at 60° it is 15.42 meters. On the WGS84 spheroid, the length in meters of a degree of latitude at latitude φ (that is, the number of meters you would have to travel along a north–south line to move 1 degree in latitude, when at latitude φ), is about The returned measure of meters per degree latitude varies continuously with latitude.
Geographic coordinate system | Length of a degree
The distance between the Antarctic Circle and the Tropic of Cancer is essentially constant as they move in tandem. See axial tilt and circles of latitude for additional details.
Tropic of Cancer | Drift
The 45th parallel south is a circle of latitude that is 45° south of the Earth's equator. It is the line that marks the theoretical halfway point between the equator and the South Pole. The true halfway point is south of this parallel because Earth is not a perfect sphere, but bulges at the equator and is flattened at the poles. Unlike its northern counterpart, almost all (97%) of it passes through open ocean. It crosses the South Atlantic Ocean, the Indian Ocean, Australasia (New Zealand and just south of Tasmania), the Southern Ocean, and Patagonia. At this latitude, daytime lasts for 15 hours, 37 minutes during the December solstice and 8 hours, 46 minutes during the June solstice.
45th parallel south | Introduction
During this time, air and water temperatures, tides, sea levels and wave heights, and relative humidity all rise. These conditions produce heavy rainfall that used to last through August, but now usually only lasts into May. Rain during the rainy season is punctuated by sunny weather.
Pacific Equatorial Forest | Climate
The atmosphere responds by generating vertical wind shear to maintain thermal wind balance. The jet reaches its zenith in August, lying between the 16th and 17th parallels. In September, winds maximize near between the 12th and 13th parallels. The easterly jet weakens and drops southward during October and November.
African easterly jet | Formation and characteristics
As the variable circumference of the earth approaches , such a maximum "diametrical" or "antipodal" line would be on the order of long.
Extreme points of Earth | Along any truly straight line
Once aloft, air flows away from the storm's center, producing a shield of cirrus clouds. The previously mentioned processes result in a nearly axisymmetric wind field: Wind speeds are low at the center, increase rapidly moving outwards to the radius of maximum winds, and then decay more gradually with radius to large radii. However, the wind field often exhibits additional spatial and temporal variability due to the effects of localized processes, such as thunderstorm activity and horizontal flow instabilities. In the vertical direction, winds are strongest near the surface and decay with height within the troposphere.
Tropical cyclone | Wind field
Even for Bricard octahedra constructed to have a flat equator, the equator generally does not remain flat as the octahedron flexes. However, for some Bricard octahedra, such as the octahedron with an antiparallelogram equator shown in the illustration, the symmetries of the polyhedron cause its equator to remain planar at all times.
Bricard octahedron | Explanation
Toby Carlson evaluated data over the eastern Caribbean sea for October 1965 and pinpointed the presence of an upper tropospheric cold-core cyclone. These cold-core cyclones generally form close to the Azores and move south and westward towards a latitude of 20°N. These circulations extend over an area of about 20° of latitude (or ) and 40° of longitude. The lowest level of closed circulation underneath the upper level cold-core cyclone is often between the 700 and the 500-hectopascal level ( to above sea level). Their life cycles span 5 to 14 days. The upper tropospheric cyclonic centers in the North Atlantic differ from that in the North Pacific.
Upper tropospheric cyclonic vortex | Climatology
If the equinox happened at night, or if the sky was cloudy, an interpolation could be made between two days' measurements.
Equatorial ring | Introduction
At higher altitudes, the winds within a tropical cyclone head away from the center, forming the outflow which produces the shape of the tropical cyclone.
Tropical cyclone windspeed climatology | Location of the winds
The Jovian bands are bounded by zonal atmospheric flows (winds), called "jets". The eastward (prograde) jets are found at the transition from zones to belts (going away from the equator), whereas westward (retrograde) jets mark the transition from belts to zones. Such flow velocity patterns mean that the zonal winds decrease in belts and increase in zones from the equator to the pole. Therefore, wind shear in belts is cyclonic, while in zones it is anticyclonic. The EZ is an exception to this rule, showing a strong eastward (prograde) jet and has a local minimum of the wind speed exactly at the equator.
Atmosphere of Jupiter | Zones, belts and jets
Strong vertical wind shear within the troposphere also inhibits tropical cyclone development, but helps to organize individual thunderstorms into living longer life cycles that can then produce severe weather. The thermal wind concept explains how differences in wind speed with height are dependent on horizontal temperature differences, and explains the existence of the jet stream.
Wind | Shear
The Arctic Circle is roughly long, as is the Antarctic Cicle.. A "true circumnavigation" of the Earth is defined, in order to account for the shape of the Earth, to be about 2.5 times as long, including a crossing of the equator, at about .. On the flat Earth model, the ratios would require the Antarctic Circle to be 2.5 times the length of the circumnavigation, or 2.5x2.5=6.25 times the length of the Arctic Circle.
Spherical Earth | Surface circumnavigation
It leads to a localized acceleration of the trade winds in the region, and can enhance thunderstorm activity when it interacts with the Intertropical Convergence Zone. The effects can last from a few hours to six days.
Tehuantepecer | Climatology
Length of day increases from the equator towards the North Pole in the Northern Hemisphere in June (around the summer solstice there), but decreases towards the South Pole in the Southern Hemisphere at the time of the southern winter solstice.
Summer solstice | Length of the day on the summer solstice of the north
Low-pressure weather systems with inward winds (such as a hurricane) spin counterclockwise north of the equator, but clockwise south of the equator. This is due to the Coriolis force, and requires that (assuming they are attached to each other and rotating in the same direction) the north and southern halves of the Earth are angled in opposite directions (e.g. the north is facing toward Polaris and the south is facing away from it).
Spherical Earth | Weather systems
Enhanced surface (upper level) westerly winds occur near the west (east) side of the active convection. Ocean currents, up to in depth from the ocean surface, follow in phase with the east-wind component of the surface winds. In advance, or to the east, of the MJO enhanced activity, winds aloft are westerly. In its wake, or to the west of the enhanced rainfall area, winds aloft are easterly. These wind changes aloft are due to the divergence present over the active thunderstorms during the enhanced phase. Its direct influence can be tracked poleward as far as 30 degrees latitude from the equator in both northern and southern hemispheres, propagating outward from its origin near the equator at around 1 degree latitude, or , per day.
Madden–Julian oscillation | Behavior
The yearly average wind speed is .
Credenhill | Climate
Despite this, much of the atmosphere outside the tropics is close to geostrophic flow much of the time and it is a valuable first approximation. Geostrophic flow in air or water is a zero-frequency inertial wave.
Geostrophic wind | Introduction
Near the equator, this means the variation in strength of solar radiation is different relative to the time of year than it is at higher latitudes: Maximum solar radiation is received during the equinoxes, when a place at the equator is under the subsolar point at high noon, and the intermediate seasons of spring and autumn occur at higher latitudes, and the minimum occurs during "both" solstices, when either pole is tilted towards or away from the sun, resulting in either summer or winter in both hemispheres. This also results in a corresponding movement of the equator away from the subsolar point, which is then situated over or near the relevant tropic circle.
Equator | Equatorial seasons and climate
These winds can last for up to six months. It has been reported that on July 8, 2003, the dew point was while the temperature was , which would indicate a heat index of , one of the highest heat indexes ever reported.
Dhahran | Climate
It is sometimes asserted that the length of the current interglacial temperature peak will be similar to the length of the preceding interglacial peak (Sangamonian/Eem Stage). Therefore, we might be nearing the end of this warm period. However, this conclusion is probably mistaken: the lengths of previous interglacials were not particularly regular (see graphic at right). Berger and Loutre (2002) argue that “with or without human perturbations, the current warm climate may last another 50,000 years. The reason is a minimum in the eccentricity of Earth's orbit around the Sun.” Also, Archer and Ganopolski (2005) report that probable future CO emissions may be enough to suppress the glacial cycle for the next 500 kyr.
Orbital forcing | Overview
Ocean currents are also important factors in determining climate, particularly the thermohaline circulation that distributes thermal energy from the equatorial oceans to the polar regions. The amount of solar energy reaching Earth's surface decreases with increasing latitude. At higher latitudes, the sunlight reaches the surface at lower angles, and it must pass through thicker columns of the atmosphere. As a result, the mean annual air temperature at sea level decreases by about per degree of latitude from the equator. Earth's surface can be subdivided into specific latitudinal belts of approximately homogeneous climate. Ranging from the equator to the polar regions, these are the tropical (or equatorial), subtropical, temperate and polar climates.
Earth | Weather and climate
There is also a bridle path that winds all the way around the circumference.
Paradisbakkerne | Conservation
Almost all wind instruments use the last method, often in combination with one of the others, to extend their register.
Wind instrument | Introduction
Major whirlwinds last longer because they are formed from very powerful winds, and it is hard, though not impossible, to interrupt them. Minor whirlwinds are not as long-lived; the winds that form them do not last long, and when a minor whirlwind encounters an obstruction (a building, a house, a tree, etc.), its rotation is interrupted, as is the windflow into it, causing it to dissipate.
Whirlwind | Duration
In modern units this is , close to the current equatorial value of .
Spherical Earth | India
The latitude of the Earth's equator is, by definition, 0° (zero degrees) of arc. The equator is one of the five notable circles of latitude on Earth; the other four are both polar circles (the Arctic Circle and the Antarctic Circle) and both tropical circles (the Tropic of Cancer and the Tropic of Capricorn). The equator is the only line of latitude which is also a great circle—that is, one whose plane passes through the center of the globe. The plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator. In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice per year: on the equinoxes in March and September.
Equator | Overview
The radius of the semi-major axis of the Earth at the equator is 6,378,137.0 m resulting in a circumference of 40,075,016.7 m. The equator is divided into 360 degrees of longitude, so each degree at the equator represents 111,319.5 m or approximately 111.32 km. As one moves away from the equator towards a pole, however, one degree of longitude is multiplied by the cosine of the latitude, decreasing the distance, approaching zero at the pole. The number of decimal places required for a particular precision at the equator is: A value in decimal degrees to a precision of 4 decimal places is precise to 11.132 m at the equator.
Decimal degrees | Precision
The Earth has a rather slight equatorial bulge: it is about wider at the equator than pole-to-pole, a difference which is close to 1/300 of the diameter. If the Earth were scaled down to a globe with diameter of 1 meter at the equator, that difference would be only 3 millimeters. While too small to notice visually, that difference is still more than twice the largest deviations of the actual surface from the ellipsoid, including the tallest mountains and deepest oceanic trenches. The rotation of the earth also affects the sea level, the imaginary surface that is used to measure altitudes from.
Equatorial bulge | On Earth
The tracking of numerous cloud features allowed determination of zonal winds blowing in the upper troposphere of Uranus. At the equator winds are retrograde, which means that they blow in the reverse direction to the planetary rotation. Their speeds are from −100 to −50 m/s. Wind speeds increase with the distance from the equator, reaching zero values near ±20° latitude, where the troposphere's temperature minimum is located. Closer to the poles, the winds shift to a prograde direction, flowing with its rotation. Wind speeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles. Wind speeds at −40° latitude range from 150 to 200 m/s.
Climate of Uranus | Winds
The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to the axial tilt of the Earth. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone). The tropics include all zones on Earth where the Sun contacts a point directly overhead at least once during the solar year (which is a subsolar point). Thus the maximum latitudes of the tropics have the same value positive and negative.
Tropics | Introduction