Table of Contents
Tropical Cyclones and Temperate Cyclones -Comparison
|Thermal Origin||Dynamic Origin – Coriolis Force, Movement of air masses.|
|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.|
|Absent||The very cyclone formation is due to frontogenesis.[Occluded Front]|
|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|
|Seasonal: Late summers (Aug – Oct)||Irregular. But few in summers and more in winters.|
|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.
|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.
|Complete circles and the pressure gradient is steep||Isobars are usually ‘V’ shaped and the pressure gradient is low.|
|Doesn’t last for more than a week||Last for 2-3 weeks.|
|East – West. Turn North at 200 latitude and west at 300 latitude.|
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.|
|The temperature at the center is almost equally distributed.||All the sectors of the cyclone have different temperatures|
|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.|
|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.)|
|The tropical cyclones exhibit fewer varieties of clouds – cumulonimbus, nimbostratus, etc..||The temperate cyclones show a variety of cloud development at various elevations.|
|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’.|
- Titbit: In certain instances, two cyclones move toward each other and revolve around one another, with the smaller and less intense one moving more quickly. This phenomenon is called the Fujlwara effect.