Question

compare the main features of the tropical and temperate cyclones

Answer 1

Tropical Cyclone

Temperate Cyclone

Origin

Thermal OriginDynamic Origin – Coriolis Force, Movement of air masses.

Latitude

Confined to 100– 300 N and S of equator.Confined to 350 – 650 N and S of equator. More pronounced in Northern hemisphere due to greater temperature contrast.

Frontal system

AbsentThe very cyclone formation is due to frontogenesis.[Occluded Front]

Formation

They form only on seas with temperature more than 26-270 C. They dissipate on reaching the land.Can form both on land as well as seas

Season

Seasonal: Late summers (Aug – Oct)Irregular. But few in summers and more in winters.

Size

Limited to small area.

Typical size: 100 – 500 kms in diameter.

Varies with the strength of the cyclone.

They cover a larger area.

Typical size: 300 – 2000 kms in diameter. Varies from region to region.

Shape

Elliptical


Inverted ‘V’


Rainfall

Heavy but does not last beyond a few hours. If the cyclone stays at a place, the rainfall may continue for many days.In a temperate cyclone, rainfall is slow and continues for many days, sometimes even weeks.

Wind Velocity and destruction

Much greater (100 – 250 kmph)(200 – 1200 kmph in upper troposphere)

Greater destruction due to winds, storm surges and torrential rains.

Comparatively low. Typical range: 30 – 150 kmph.

Less destruction due to winds but more destruction due to flooding.

Isobars

Complete circles and the pressure gradient is steepIsobars are usually ‘V’ shaped and the pressure gradient is low.

Life time

Doesn’t last for more than a weekLast for 2-3 weeks.

Path

East – West. Turn North at 200 latitude and west at 300latitude.

Move away from equator.

The movement of Cyclones in Arabian Sea and Bay of Bengal is a little different.

Here, these storms are superimposed upon the monsoon circulation of the summer months, and they move in northerly direction along with the monsoon currents.


West – East (Westerlies – Jet Streams). Move away from equator.



Temperature distribution

The temperature at the center is almost equally distributed.All the sectors of the cyclone have different temperatures

Calm region

The center of a tropical cyclone is known as the eye. The wind is calm at the center with no rainfall.In a temperate cyclone, there is not a single place where winds and rains are inactive.

 

Driving force

The tropical cyclone derives its energy from the latent heat of condensation, and the difference in densities of the air masses does not contribute to the energy of the cyclone.The energy of a temperate cyclone depends on the densities of air masses.

 

Influence of Jet streams

The relationship between tropical cyclones and the upper level air-flow is not very clear.The temperate cyclones, in contrast, have a distinct relationship with upper level air flow (jet streams, Rossby waves etc.)



Clouds

The tropical cyclones exhibit fewer varieties of clouds – cumulonimbus, nimbostratus, etc..The temperate cyclones show a variety of cloud development at various elevations.



Surface anti-cyclones

The tropical cyclones are not associated with surface anticyclones and they have a greater destructive capacity.The temperate cyclones are associated with anticyclones which precede and succeed a cyclone. These cyclones are not very destructive.

Influence on India

Both coasts effected. But east coast is the hot spot.Bring rains to North – West India. The associated instability is called ‘Western Disturbances’.