can sum1 explain to me bout da cyclonic winds and monsoon winds???

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  • Anonymous
    1 decade ago
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    CYCLONIC WINDS:any large system of winds that rotates about a centre of low atmospheric pressure in a counterclockwise direction north of the Equator and in a clockwise direction to the south. Cyclonic winds move across nearly all regions of the Earth except the equatorial belt and are generally associated with rain or snow. Also occurring in much the same areas are anticyclones. They r torential in nature.


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  • 1 decade ago

    In meteorology, a cyclone is an area of low atmospheric pressure characterised by inward spiraling winds that spin counterclockwise in the northern hemisphere of the Earth, and clockwise in the southern hemisphere.[1][2] Covering a wide variety of meteorological phenomena such as tropical cyclones, extratropical cyclones and tornadoes, the generic term is rarely used by meteorologists without a qualifierEtymology

    There are several theories on the origin of the term cyclone. The word appears to have been used first by Henry Piddington around 1840. It may have been derived from the Greek word kyklon, which means moving in a circle,[3][4]. Some say that Piddington derived the word from the Greek word cyclos, meaning "coils of a snake", in comparison with the tropical storms in the Bay of Bengal and in the Arabian Sea. [5] Others argue that the word was derived from Cyclops, a creature in Greek mythology with one eye, as it is 'turning wind with one eye'.[6]

    [edit] Structure

    There are a number of structural characteristics common to all cyclones. Their center is the area of lowest atmospheric pressure, often known in mature tropical and subtropical cyclones as the eye. Near the center, the pressure gradient force (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure. The wind flow around a large cyclone is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere as a result of the Coriolis effect.

    [edit] Categorisation

    Each type of cyclone has further characteristics which define it as a Polar cyclone, Polar low, Extratropical, Subtropical, Tropical, or Mesoscale (to name the six major types).

    [edit] Polar cyclone

    Main article: Polar cyclone

    Polar or Arctic cyclones are vast areas of low pressure. They should not be confused with what are commonly referred to as polar lows, which behave like hurricanes. A polar cyclone is a low pressure weather system, usually spanning 1,000–2,000 kilometers, in which the air circulates in a counterclockwise fashion in the northern hemisphere.

    [edit] Polar low

    Polar low over the Barents Sea on February 27, 1987Main article: Polar low

    A polar low is a small-scale, short-lived atmospheric low pressure system (depression) that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres. The systems usually have a horizontal length scale of less than 1,000 km and exist for less than a couple of days. They are part of the larger class of mesoscale weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and oil platforms.

    Polar lows have been referred to by many other terms, such as comma cloud, mesocyclone, polar mesoscale vortex, Arctic hurricane, Arctic low, and cold air depression. Today the term is usually reserved for the more-vigorous systems that have near-surface winds of at least gale force (17 m/s).

    [edit] Extratropical

    A ficticious synoptic chart of an extratropical cyclone affecting the UK. The blue arrows between isobars indicate the direction of the wind, while the "L" symbol denotes the center of the "low". Note the occluded, cold and warm frontal boundaries.Main article: Extratropical cyclone

    An extratropical cyclone, sometimes inaccurately called a cyclone, is a synoptic scale low pressure weather system that has neither tropical or polar characteristics, being connected with fronts and horizontal gradients in temperature and dew point otherwise known as "baroclinic zones".[7]

    The descriptor "extratropical" refers to the fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet. These systems may also be described as "mid-latitude cyclones" due to their area of formation, or "post-tropical cyclones" where extratropical transition has occurred,[7][8] and are often described as "depressions" or "lows" by weather forecasters and the general public. These are the everyday phenomena which along with anti-cyclones, drive the weather over much of the Earth.

    Although extratropical cyclones are almost always classified as baroclinic since they form along zones of temperature and dewpoint gradient, they can sometimes become barotropic late in their life cycle when the temperature distibution around the cyclone becomes fairly uniform with radius.

    [edit] Subtropical

    Main article: Subtropical cyclone

    A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form in a wide band of latitude, from the equator to 50°.

    [edit] Tropical

    Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004Main article: Tropical cyclone

    A tropical cyclone is a storm system fueled by the heat released when moist air rises and the water vapor in it condenses. The term describes the storm's origin in the tropics and its cyclonic nature, which means that its circulation is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Tropical cyclones are distinguished from other cyclonic windstorms such as nor'easters, European windstorms, and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems.

    Depending on their location and strength, there are various terms by which tropical cyclones are known, such as hurricane, typhoon, tropical storm, cyclonic storm and tropical depression.

    Tropical cyclones can produce extremely strong winds, tornadoes, torrential rain, high waves, and storm surges. The heavy rains and storm surges can produce extensive flooding. Although their effects on human populations can be devastating, tropical cyclones also can have beneficial effects by relieving drought conditions. They carry heat away from the tropics, an important mechanism of the global atmospheric circulation that maintains equilibrium in the Earth's troposphere.

    [edit] Mesoscale

    Main article: Mesocyclone

    A mesocyclone is a cyclonic vortex of air, between approximately 2 and 10 km diameter within a convective storm. They can often be found in association with updrafts in supercells, where tornadoes may form. The term refers only to mesoscale cyclones found within convective storms, and does not apply to other cyclones on the mesoscale.[9] Storms with mesocyclones can feature strong surface winds and severe hail.

    [edit] Cyclone as metaphor

    Cyclone as metaphor for political revolution: a woman ('Democratic Party') hiding in a storm cellar from a tornado, often called a "cyclone" in the early 20th century.The cyclone has been used for over 100 years as a metaphor for political upheaval.[10] For example, according to political interpretations of The Wizard of Oz, the cyclone takes Dorothy to a utopia (Oz), and kills the Wicked Witch of the East who had oppressed the little people (the Munchkins).[10] The storm cellar has also been used as a metaphor for seeking safety, as the 1894 cartoon shows. The caption reads, "In the cyclone cellar, waiting for fair weather."

    A monsoon is a wind pattern that reverses direction with the seasons. The term was originally applied to seasonal winds in the Indian Ocean and Arabian Sea. The word is also used more specifically for the season in which this wind blows from the southwest in India and adjacent areas that is characterized by very heavy rainfall, and especially, for the rainfall associated with this wind.

    In terms of total precipitation, total area covered and the total number of people affected, the monsoon affecting the Indian Subcontinent dwarfs the North American monsoon (also called the "Mexican", "southwest", "desert", or "Arizona" monsoon).


    Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of India and Asia around 50 million years ago. Evidence for when this first happens has remained controversial. Many geologists believe that the monsoon first became strong around 8 million years ago based on records from the Arabian Sea and the record of wind blown dust in the Loess Plateau of China. More recently plant fossils in China and new long duration sediment records from the South China Sea lead Peter Clift to propose a much older monsoon starting around 24 million years ago and linked to early Tibetan uplift. Testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to global climate change, especially the cycle of the Pleistocene ice ages.

    [edit] Processes

    Monsoons are caused by the larger amplitude of the seasonal cycle of temperature over land as compared to the adjacent oceans. This differential warming results from the fact that heat in the ocean is mixed vertically through a "mixed layer" that may be 50 meters deep, through the action of wind and buoyancy-generated turbulence, whereas the land surface conducts heat slowly, with the seasonal signal penetrating perhaps a meter or so. Additionally, the specific heat of liquid water is significantly higher than that of most materials that make up land. Together, these factors mean that the heat capacity of the layer participating in the seasonal cycle is much larger over the oceans than over land, with the consequence that land warms faster and reaches a higher temperature than the ocean. The hot air over the land tends to rise, creating an area of low pressure. This creates a steady wind blowing toward the land, bringing the moist near-surface air over the oceans with it. Associated rainfall is caused by the moist ocean air being lifted upward by mountains, surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows at the surface. However the lifting occurs, the air cools due to adiabatic expansion, which in turn produces condensation.

    In winter, the land cools off quickly, but the ocean retains heat longer. The hot air over the ocean rises, creating a low pressure area and a breeze from land to ocean while a large area of high pressure is formed over the land, intensified by wintertime radiational cooling.

    Monsoons are similar to sea breezes, a term usually referring to the localized, diurnal (daily) cycle of circulation near coastlines everywhere, but they are much larger in scale, stronger and seasonal.

    [edit] Monsoon systems

    As monsoons have become better understood, the term monsoon has been broadened to include almost all of the phenomena associated with the annual weather cycle within the tropical and subtropical land regions of the earth.

    Even more broadly, it is now understood that in the geological past, monsoon systems must have always accompanied the formation of supercontinents such as Pangaea, with their extreme continental climates.

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