World Geography / Climatology
Cyclone is an intense form of weather disturbance. There are two different types of cyclones that occur around the world namely, Tropical
cyclones and Temperate cyclones.
Structure of a Cyclone
Cyclone is a narrow intense low pressure zone surrounded by high pressure zone. Winds converge into low pressure zone added by Coriolis force and
hence become spiraling or gyratory in nature. That is why we have very heavy rainfall of higher intensity accompanied by lightning and thunder. These strong
spiraling winds are referred to as Gales and these may reach up to 200 kmph.
The approach of a Cyclone can be identified if there is (i) sudden and steep rise in temperature of surface area, (ii) sudden and abnormal decrease in
pressure, (iii) sudden change in the wind direction ( like W to E becomes E to W ) and (iv) change in the cloud structure.
Types of Clouds
Clounds can be of different types depending on the Altitude and the Structure
Types of Clouds based on Altitude
- Cirrus Clouds - These are high altitude clouds occurring above 5km. These are made of ice and are milky white ( transparent ) in colour. Cirrus clouds
always have quiet and pleasant weather.
- Altocumulus Clouds - These are mid altitude clouds occurring between 2-5 km and they are having ice and water.
- Nimbus Clouds - These are low altitude clouds occurring below 2km and are having only water in it. These are bluish in colour.
Types of Clouds based on Structure
- Cumulous Clouds - These are having the structure of a lamp or they are in the form of Puff (cabbage or cauliflower structure).
- Stratus Clouds - These are stratified or graded in nature. They extend over horizontal planes.
There can all combinations clouds like Cirrostratus, Nimbostratus, Cumulonimbus, etc. The increasing order of intensity of clouds is Cirrus, Cirrocumulous,
Nimbus, Nimbostratus and finally Cumulonimbus.
These are vertically hanging clouds. They are extremely dark in colour ( dark grey or dark black ). They are having devilish and frightening appearance.
These are associated with highest turbulent weather conditions. Cyclones are associated with Cumulonimbus clouds and will be having cloud bursts, thundering
Types of Cyclones
There are mainly two types of cyclones, Tropical cyclones and Temperate cyclones
- Tropical cyclones are called Hurricanes in Caribbean Sea area, Toofan or Chakrawat in Indian Ocean area, Typhoons in Japan Sea, China
Sea and Korean peninsula and Willy-willy in North West Australia.
- Tropical cyclones always form in the sea or ocean and they never form on the land. When they reach the continents, they become weak. While crossing
the coast, they are disastrous. The area of these Cyclones is less, occupying a diameter of 100-120km.
- The eye ( central part ) of the cyclone is quiet, pleasant and tranquil. There will be small descending currents inside the eye. The weather outside the
eye is very much disturbed. Energy is provided by humidity or latent heat present in the air masses.
- Forecasting and monitoring these cyclones is somewhat difficult as they don't have well defined path. The path may change any time. Their general
direction is from South-East to North-West.
Temperate Cyclones ( Frontal Cyclones )
- Temperate cyclones occur in mid-latitudes of US, Western and North-Western Europe. They appear near a Front, which is nothing but a narrow zone
separating two contracting and converging air masses.
- They are formed on the land as well as on the sea. They will not dissipate while approaching the land. They are much larger in size extending up to
800-1000km diameter and whole of the area of the Cyclone will be disturbed.
- They are formed because of the thermal gradient across the Front. Higher the thermal gradient, stronger will be the Cyclone. Forecasting and
monitoring them is easier. They are steered by Westerlies. And they have well defined direction ( from West to East ).
These two types of cyclones are occurring in lower Troposphere i.e. up to 5–7km. In upper layer of the Troposphere and in Stratosphere, the weather
is stable, calm and quiet. There are slow and shifting winds here. They blow from West to East, which are called Upper Air Westerlies. There is no moisture