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Essay on Cyclone
Essay Contents:
- Essay on the Meaning of Cyclone
- Essay on the Structure of Cyclone
- Essay on the Formation of Cyclone
- Essay on the Types of Cyclones
- Essay on the Preventive Measure for Cyclone
- Essay on the District Contingency Plan for Cyclone
Essay # 1. Meaning of Cyclone:
In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterised by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale cyclonic circulations are centered on areas of low atmospheric pressure.
The largest low-pressure systems are cold-core polar cyclones and extra-tropical cyclones which lie on the synoptic scale. Warm-core cyclones such as tropical cyclones, meso-cyclones, and polar lows lie within the smaller meso-scale. Subtropical cyclones are of intermediate size.
Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the Tropical Upper Tropospheric Trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on other planets outside of the Earth, such as Mars and Neptune.
Cyclogenesis describes the process of cyclone formation and intensification. Extra-tropical cyclones form as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract to form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, cyclones occlude as cold core systems. A cyclone’s track is guided over the course of its 2 to 6 day life cycle by the steering flow of the cancer or subtropical jet stream.
Weather fronts separate two masses of air of different densities and are associated with the most prominent meteorological phenomena. Air masses separated by a front may differ in temperature or humidity. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. They form west of the circulation center and generally move from west to east.
Warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. They move pole-ward ahead of the cyclone path. Occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center.
Tropical cyclogenesis describes the process of development of tropical cyclones. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core. Cyclones can transition between extra-tropical, subtropical, and tropical phases under the right conditions. Meso-cyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from meso-cyclones, but more often develop from environments of high instability and low vertical wind shear.
Essay # 2. Structure of Cyclone:
There are a number of structural characteristics common to all cyclones. As they are low pressure areas, their center is the area of lowest atmospheric pressure in the region, often known in mature tropical 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. (An anticyclone, on the other hand, rotates clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere.)
Essay # 3. Formation of Cyclone:
Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low pressure area). Cyclogenesis is an umbrella term for several different processes, all of which result in the development of some sort of cyclone. It can occur at various scales, from the micro-scale to the synoptic scale. Extra-tropical cyclones form as waves along weather fronts before occluding later in their life cycle as cold core cyclones. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core.
Meso-cyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from meso-cyclones, but more often develop from environments of high instability and low vertical wind shear. Cyclogenesis is the opposite of cyclolysis, and has an anti-cyclonic (high pressure system) equivalent which deals with the formation of high pressure areas—Anti-cyclogenesis.
The surface low has a variety of ways of forming. Topography can force a surface low when dense low-level high pressure system ridges in east of a north-south mountain barrier. Meso-scale convective systems can spawn surface lows which are initially warm core. The disturbance can grow into a wave-like formation along the front and the low will be positioned at the crest. Around the low, flow will become cyclonic, by definition.
This rotational flow will push polar air equator-ward west of the low via its trailing cold front, and warmer air with push pole-ward low via the warm front. Usually the cold front will move at a quicker pace than the warm front and “catch up” with it due to the slow erosion of higher density air mass located out ahead of the cyclone and the higher density air mass sweeping in behind the cyclone, usually resulting in a narrowing warm sector. At this point an occluded front forms where the warm air mass is pushed upwards into a trough of warm air aloft, which is also known as a trowel.
Tropical cyclogenesis is the technical term describing the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favourable atmospheric environment.
There are six main requirements for tropical cyclogenesis – sufficiently warm sea surface temperatures, atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low pressure center, a pre-existing low level focus or disturbance, and low vertical wind shear. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones (at least Category 3 intensity on the Saffir-Simpson Hurricane Scale).
Meso-cyclones are believed to form when strong changes of wind speed and/or direction with height (“wind shear”) sets parts of the lower part of the atmosphere spinning in invisible tube-like rolls. The convective updraft of a thunderstorm is then thought to draw up this spinning air, tilting the rolls’ orientation upward (from parallel to the ground to perpendicular) and causing the entire updraft to rotate as a vertical column.
Meso-cyclones are normally relatively localized – they lie between the synoptic scale (hundreds of kilometers) and micro-scale (hundreds of meters). Radar imagery is used to identify these features.
Essay # 4. Types of Cyclones:
Surface-Based Types:
There are six main types of cyclones:
1. Polar cyclones,
2. Polar lows,
3. Extra-tropical cyclones,
4. Subtropical cyclones,
5. Tropical cyclones, and
6. Meso-cyclones
1. Polar Cyclone:
A polar, sub-polar, or Arctic cyclone (also known as a polar vortex) is a vast area of low pressure which strengthens in the winter and weakens in the summer. A polar cyclone is a low pressure weather system, usually spanning 1,000 kilometres (620 mi) to 2,000 kilometres (1,200 mi), in which the air circulates in a counterclockwise direction in the northern hemisphere, and a clockwise direction in the southern hemisphere. In the Northern Hemisphere, the polar cyclone has two centers on average.
One center lies near Baffin Island and the other over northeast Siberia. In the southern hemisphere, it tends to be located near the edge of the Ross Ice Shelf near 160 west longitude. When the polar vortex is strong, westerly flow descends to the Earth’s surface. When the polar cyclone is weak, significant cold outbreaks occur.
2. Polar Low:
A polar low is a small-scale, short-lived atmospheric low pressure system (depression) that is found over the ocean areas pole-ward 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 kilometres (620 mi) and exist for no more than a couple of days. They are part of the larger class of meso-scale 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 polar meso-scale 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 17 m/s.
3. Extra-Tropical Cyclone:
An extra-tropical cyclone is a synoptic scale low pressure weather system that has neither tropical nor polar characteristics, being connected with fronts and horizontal gradients in temperature and dew point otherwise known as “baroclinic zones”.
The descriptor “extra-tropical” 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 extra-tropical transition has occurred, 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 extra-tropical cyclones are almost always classified as baroclinic since they form along zones of temperature and dew-point gradient within the westerlies, they can sometimes become barotropic late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform with radius. An extra-tropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone, if it dwells over warm waters and develops central convection, which warms its core.
4. Subtropical Cyclone:
A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extra-tropical cyclone. They can form between the equator and the 50th parallel. As early as the 1950s, meteorologists were unclear whether they should be characterised as tropical cyclones or extra-tropical cyclones, and used terms such as quasi-tropical and semi-tropical to describe the cyclone hybrids.
By 1972, the National Hurricane Center officially recognized this cyclone category. Subtropical cyclones began to receive names off the official tropical cyclone list in the Atlantic Basin in 2002. They have broad wind patterns with maximum sustained winds located farther from the center than typical tropical cyclones, and exist in areas of weak to moderate temperature gradient.
Since they form from initially extra-tropical cyclones which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required for their formation are lower than the tropical cyclone threshold by three degrees Celsius, or five degrees Fahrenheit, lying around 23 degrees Celsius. This means that subtropical cyclones are more likely to form outside the traditional bounds of the hurricane season. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.
5. Tropical Cyclone:
A tropical cyclone is a storm system characterised by a low pressure center and numerous thunderstorms that produce strong winds and flooding rain. A tropical cyclone feeds on heat released when moist air rises, resulting in condensation of water vapour contained in the moist air. They are fueled by a different heat mechanism than other cyclonic windstorms such as nor’easters, European windstorms, and polar lows, leading to their classification as “warm core” storm systems.
The term “tropical” refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe, and their formation in Maritime Tropical air masses. The term “cyclone” refers to such storms’ cyclonic nature, with counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere.
Depending on their location and strength, tropical cyclones are referred to by other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply as a cyclone. Generally speaking, a tropical cyclone is referred to as a hurricane (from the name of the ancient Central American deity of wind, Hurricane) in the Atlantic basin, and a Cyclone in the Pacific.
While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge. They develop over large bodies of warm water, and lose their strength if they move over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding inland, and storm surges can produce extensive coastal flooding up to 40 kilometres (25 mi) from the coastline.
Although their effects on human populations can be devastating, tropical cyclones can also relieve drought conditions. They also carry heat and energy away from the tropics and transport it toward temperate latitudes, which make them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth’s troposphere.
Many tropical cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere are favourable. Others form when other types of cyclones acquire tropical characteristics. Tropical systems are then moved by steering winds in the troposphere; if the conditions remain favourable, the tropical disturbance intensifies, and can even develop an eye.
On the other end of the spectrum, if the conditions around the system deteriorate or the tropical cyclone makes landfall, the system weakens and eventually dissipates. A tropical cyclone can become extra-tropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses. From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extra-tropical transition.
6. Meso-Cyclone:
A meso-cyclone is a vortex of air, approximately 2.0 kilometres (1.2 mi) to 10 kilometres (6.2 mi) in diameter (the meso-scale of meteorology), within a convective storm. Air rises and rotates around a vertical axis, usually in the same direction as low pressure systems in both northern and southern hemisphere. They are most often cyclonic, that is, associated with a localised low-pressure region within a severe thunderstorm. Such storms can feature strong surface winds and severe hail. Meso-cyclones often occur together with updrafts in super-cells, where tornadoes may form. About 1700 meso-cyclones form annually across the United States, but only half produce tornadoes.
Cyclones are not unique to Earth. Cyclonic storms are common on Jovian planets, like the Small Dark Spot on Neptune. Also known as the Wizard’s Eye, it is about one third the diameters of the Great Dark Spot. It received the name “Wizard’s Eye” because it looks like an eye. This appearance is caused by a white cloud in the middle of the Wizard’s Eye. Mars has also exhibited cyclonic storms. Jovian storms like the Great Red Spot are usually mistakenly named as giant hurricanes or cyclonic storms. However, this is inaccurate, as the Great Red Spot is, in fact, the inverse phenomenon, an anticyclone.
Upper Level Types:
Under specific circumstances, upper cold lows can break off from the base of the Tropical Upper Tropospheric Trough (TUTT), which is located mid-ocean in the Northern Hemisphere during the summer months. These upper tropospheric cyclonic vortices, also known as TUTT cells or TUTT lows, usually move slowly from east-northeast to west- southwest, and generally do not extend below 20,000 feet in altitude. A weak inverted surface trough within the trade wind is generally found underneath them, and they may also be associated with broad areas of high-level clouds.
Downward development results in an increase of cumulus clouds and the appearance of a surface vortex. In rare cases, they become warm-core, resulting in the vortex becoming a tropical cyclone. Upper cyclones and upper troughs which trail tropical cyclones can cause additional outflow channels and aid in their intensification process. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet emanating from the developing tropical disturbance/cyclone.
Essay # 5.
Preventive Measures for Cyclone:
In the event of cyclonic disaster, following do and don’t are very important and crucial:
1. Check houses, secure loose tiles by cementing wherever necessary, repair doors and windows.
2. Check the area around the house. Remove dead or dying trees, anchor removable objects like lumber piles, loose bricks, garbage cans, sign-boards, loose zinc sheets etc.
3. Keep some wooden boards ready so that glass windows can be boarded.
4. If you do not have wooden boards handy, paste paper strips on glasses to prevent splinters flying into the house.
5. Keep a hurricane Lantern filled with kerosene, flash light and enough dry cells and keep them handy.
6. Promptly demolish condemned buildings.
7. Those who have radio sets should ensure that the radio is fully serviceable. In the case of transistors an extra set of batteries should be kept handy.
8. Keep your radio on and listen to latest weather warnings and advisories from the nearest AIR station. Pass the information to others.
9. Pass only the official information you have got from the radio to others.
10. Get away from low lying beaches or other locations which may be swept by high tides or storm waves. Leave sufficiently early before your way to high ground gets flooded. Do not delay and run the risk of being marooned.
11. If your house is out of danger from high tides and flooding from the river, and it is well built, it is then probably the best place. However, please act promptly if asked to evacuate.
12. Be alert for high water in areas where streams of rivers may flood due to heavy rains.
13. Get extra food, especially things which can be eaten without cooking or with very little preparation. Store extra drinking water in suitably covered vessel.
14. If you are in one of the evacuation areas, move your valuable articles to upper floors to minimise flood damage.
15. Check on everything that might blow away or be torn loose. Kerosene tins, cans, agricultural implements, garden tools, road signs and other objects become weapon of destruction in strong winds. Remove them and store them in a covered room.
16. Be sure that a window or door can be opened on the lee side of the house i.e., the side opposite the one facing the wind.
17. Make provisions for children and adults requiring special diets.
18. If the centre of ‘eye’ of the storm passes directly over your place, there will be a lull in the wind and rain, lasting for half an hour or more. During this period stay in safe place. Make emergency repairs during the lull period if necessary, but remember that strong wind will return suddenly from the opposite direction, frequently with even greater violence.
19. Be calm. Your ability to meet emergency will inspire and help others.
20. You should remain in shelters until informed by those in charge that you may return home.
21. Any loose and dangling wire from the lamp post should be strictly avoided.
22. People should keep away from disaster areas unless you are required to assist.
23. Anti-social elements should be prevented from doing mischief and reported to the police.
24. Cars, buses, lorries and carts should be driven carefully.
25. The houses and dwellings should be cleared of debris.
26. The losses should be reported to the appropriate authorities.
27. Relatives should be promptly informed about the safety of persons in the disaster area.
Don’ts:
1. Avoid being misled by rumours.
2. Don’t leave shelters until informed by the rescue personals.
3. Don’t leave the safer place during lull, however minor repairs can be carried out.
4. Don’t touch the loose and dangling wire from lamp post, it may have electric current.
Essay # 6.
District Contingency Plan for Cyclone:
Action Points:
A. Action after the First Warning:
The Collector should ensure:
I. That sufficient stock of food grains, kerosene and other dry food commodities are available for distribution to the victims.
II. That Medical and Veterinary Departments are fully equipped with required Drugs and Vaccines for taking preventive steps after cyclone and to arrest the spread of epidemics.
III. That all the Government vehicles are kept in road-worthy condition for putting them to use in the emergency.
IV. That a list of generators available with the Cinema Theatres and other undertakings is maintained by the officials of State Electricity Board and advance action taken immediately to procure them when necessity arises.
V. That action is taken for opening of cyclone stores for providing the following materials.
VI. Hooks of the type available with the Fire Service Department for cleaning debris.
VII. Rubber tyres and tubes for using as floats in water.
VIII. Tents
IX. Kerosene lanterns.
X. Large cooking vessels for use in relief camps.
XI. Identify slips to be issued to be victims in relief camps.
XII. Copies of maps, etc.
XIII. Ropes, wires, chains, lights, with wire fittings, lead wires, torches, etc.
XIV. Spare Road Market Stores, Steel poles, Bamboos, G.C. Sheets, and Slotted Stripes of metal (to be laid on chured up road surface for better transportation).
XV. Double handle shows (for cutting fallen trees), Shovels, Candles, Land Hailers, Hose pipes, first aid kits, cyclone duty sign Boards, Rodes, Asbestos, Sheets, Torch lights, Detty, cans, empty oil drums, gunny bags and sand bags, polythene bags, (for dropping supplies), buckets, V.H.E. sets with batteries for use.
XVI. Fodders, pumps for bailing out water along with hose spedes, crow bars, hard gloves, Eucalyptus oil, napathalene balls, bamboo mats, phenyle slate line, etc., useful for burying dead bodies.
B. Action after Receipt of the Second Warning:
I. Evaluation
II. Relief to Stranded persons
III. Stoppage of traffic on National Highways
IV. Stock of foodgrains
V. Declaration of local holiday to the educational institutions
C. Post-Cyclone Measures:
I. Convening of the meetings of the committees.
II. Rescue operations.
III. Removal of dead bodies and carcasses.
IV. Health measures.
V. Restoration of traffic.
VI. Adequate number of mobile squads shall also made available by the Police Department for helping clearing the fallen trees, etc.
VII. Electricity Board should clear the roads of fallen electric poles and restore power supply as quickly as possible.
VIII. The Public Relations Department must ensure to build up photographic record of the damage simultaneously, using services of the local officers or by employing local man.
IX. Immediately after the cyclone, the Divisional Revenue officers should form required number of teams to assess damage to the houses, crops, loss of human lives, livestock etc.