Temperate cyclones form when two opposing air masses collide, such as light tropical air masses and thick polar air masses. Temperate cyclones are also known as Extra-tropical cyclones. The term "Extra-tropical" refers to the fact that this type of cyclone occurs outside of the tropics, with a latitude range of 30° to 60°. This article will explain to you about Temperate Cyclones which will be helpful in preparing Geography for the UPSC Civil service exam.

Cyclones

• Cyclones are a type of low-pressure environment with rapid inward air circulation. In the Northern Hemisphere, air flows counterclockwise, while in the Southern Hemisphere, it circulates clockwise.
• Storms and poor weather are frequently associated with cyclones.
• The word Cyclone comes from the Greek word Cyclos, which means snake coils.
• Henry Paddington invented the term because tropical storms in the Bay of Bengal and the Arabian Sea resemble coiled sea serpents.

Types of Cyclones

Cyclones are of two types:

1. Tropical cyclones
2. Temperate cyclones(also called Extratropical cyclones or middle-latitude cyclones or Frontal cyclones or Wave Cyclones).

What are Temperate Cyclones?

• Storm systems that form outside of the tropics, in the mid and high latitudes, are known as Extra-Tropical Cyclones.
• Cold fronts, warm fronts, and occluded fronts are all related to low-pressure systems.
• The polar front is where these cyclones form.
• Mid-latitude storms and baroclinic storms are other names for extratropical cyclones.

Origin and Development of Temperate Cyclones

Polar Front Theory

• According to this theory, warm-humid air masses from the tropics collide with dry-cold air masses from the poles, forming a polar front as a discontinuous surface.
• Such circumstances can be seen along the Tropopause and in subtropical high and subpolar low-pressure belts.
• The warm air from beneath is pushed upwards by the cold air. As a result of the reduced pressure, a void is generated. The surrounding air rushed in to fill the void, and when combined with the earth's rotation, a cyclone forms, which moves westward (Jet Streams).

Development

• The development of temperate cyclones can be studied in five stages namely

1. Stage I: Stationary/ Beginning
2. Stage II: Beginning of Young Adult
3. Stage III: Mature
4. Stage IV: Occlusion
5. Stage V: Dissipation

• Warm air blows from the south and cold air from the north of the front in the northern hemisphere.
• When the pressure drops along the front, warm air goes north and cold air moves south, causing an anticlockwise cyclonic circulation to form (northern hemisphere). The Coriolis Force is to blame for this.
• A well-developed extratropical cyclone with a warm front and a cold front results from the cyclonic circulation.
• Between the forward and rear cold air or cold sectors, there are pockets of warm air or warm sectors.
• Warm air glides over cold air, causing precipitation as a series of clouds form across the sky ahead of the warm front.
• The warm air is pushed up by the cold front as it approaches from behind. Cumulus clouds form along the cold front as a result.
• The cold front advances quicker than the warm front and eventually overtakes it.
• The cyclone evaporates once the warm air is completely pushed up and the front is occluded (occluded front).
• Wind circulation activities at the surface and aloft are intricately interrelated.
• As a result, the temperate cyclone has a lot of frontogenesis going on, mostly with occlusion type fronts. (See prior postings for more information on the occluded front.)
• Individual frontal cyclones usually last 3 to 10 days and move in a west to east path.
• The orientation of the polar jet stream in the upper troposphere controls the precise movement of this weather phenomenon.

Seasonal Occurrence of Temperate Cyclones

• Temperate cyclones are most common in the winter, late autumn, and early spring. Rainstorms and overcast weather are commonly connected with them.
• During the summer, all temperate cyclone routes travel northwards.
• There are few temperate cyclones over the subtropics and warm temperate zone, despite a large concentration of storms over the Bering Strait, the United States, and the Russian Arctic and sub-Arctic zones.

Distribution of Temperate Cyclones

• Temperate cyclones form in the world's mid-latitude regions, as previously stated.
• This region is also referred to as extra-tropical (beyond tropical).
• Temperate cyclones are mostly found between 350 and 650 degrees north and south latitude.
• Their traces have been discovered beyond 650 degrees latitude in both hemispheres.
• The prevalence and distribution of temperate cyclones reveal a well defined zone over the globe's map.
• Temperate cyclones can be found practically all year round, with some seasonal changes.
• However, they are more common in the winter since there is a higher temperature disparity.
• As a result, winter is the best time for temperate cyclones to form, and their frequency is also higher.

Structure of Temperate Cyclones

• The cold sector is in the north-west, whereas the warm sector is in the north-east (Because cold air masses in the north and warm air masses in the south push against each other and rotate anti-clockwise in the northern hemisphere).

Characteristics of Temperate Cyclones

1. Size and Shape:

• The temperate cyclones are asymmetrical and inverted 'V-shaped.
• They cover a distance of 500 to 600 kilometres.
• They may cover a distance of 2500 kilometres throughout North America (Polar Vortex).They range in height from 8 to 11 kilometres.

2. Wind Velocity And Strength:

• Winds are stronger in the eastern and southern parts of the country, and in North America than in Europe.
• The wind speed increases as the storm approaches, but drops as it passes.

3. Orientation And Movement:

• In temperate cyclogenesis, the jet stream is quite important.
• Temperate cyclones are similarly influenced by jet streams.
• These cyclones are orientated east-west because they move with the westerlies (Jet Streams).
• If the storm front is moving east-west, the centre will travel east quickly.
• The centre moves northwards if the storm front is oriented northwards, but the pressure difference decreases after two or three days, and the cyclone evaporates.
• If the storm front is directed south, the core of the storm moves fairly far south, even up to the Mediterranean region .

Associated Weather

• A temperate cyclone's arrival is signalled by a drop in temperature, a drop in mercury level, wind shifts, a halo around the sun and moon, and a thin layer of cirrus clouds.
• A little drizzle follows, eventually turning into a torrential downpour.
• The approach of the warm front, which halts the fall in mercury levels and raises the temperature, changes these conditions.
• Rainfall ends and clear weather reigns until an anticyclonic cold front comes, bringing with it a drop in temperature, cloudiness, and rain with thunder.
• After that, the weather becomes clear once more.
• When temperate cyclones move slowly and there is a significant difference in rainfall and temperature between the front and back of the cyclone, more rain falls.
• Anticyclones are usually accompanied by these cyclones.

Management of Cyclones

There are numerous structural and non-structural methods that can be used to effectively handle cyclone disasters.

1. Structural Methods: Construction of cyclone shelters, cyclone-resistant buildings, road links, culverts, bridges, canals, drains, saline embankments, surface water tanks, communication and power transmission networks, and other structural measures are among the structural measures.
2. Non-Structural Methods: The measures such as early warning dissemination systems, coastal zone management, catastrophe risk management, and capacity building of all players are involved in this type.

Under the National Cyclone Risk Mitigation Project (NCRMP), which is being implemented with World Bank assistance, these measures are being adopted and addressed on a state-by-state basis.

Significance of Temperate Cyclones

• Temperate cyclones bring rain to most of North and North-western India, filling the void left by the South West monsoon.
• Temperate cyclones are extremely important in agriculture.
• Because of the Temperate cyclones, most Rabi crops, especially wheat, in North and North-western India produce superior results.
• They also play an important role in meeting water demands for human consumption .

Conclusion

Though the effects of cyclones on human populations are threatening and devastating, tropical cyclones can also relieve drought conditions. Besides, cyclones are not only observed on Earth but also on planets like Mars, Jupiter, and Neptune. Thus cyclones are not only important in daily life but also in the UPSC Examination.