ITCZ Inter-Tropical Convergence Zone UPSC IAS G.K
Inter Tropical Convergence Zone (ITCZ) also known as Doldrums are areas of low pressure around the Equator where Trade Winds converge.
WHY DOES ITCZ FORM?
- ITCZ is the belt of Low Pressure circumventing the Earth. It is an imaginary line/area/zone which shifts towards the north & south throughout the year.
- Converging Trade Winds: North-Easterly Trade Winds & South-Eastery Trade Winds.
- ITCZ is not the Equator.
- North-Esterly Trade Winds Deflect towards the right of their line of path whereas South-Easterly Trade Winds deflect towards the left due to Coriolis Effect.
- Since winds travel from High Pressure to Low Pressure, the trade winds approach the equator from both hemispheres and eventually converge at the ITCZ (zone of low pressure).
- Convergence of trade winds results in their rising up and eventually forming clouds. Air rises up because the ITCZ is a region of low pressure (heated land) leading to the heating up of air. The air then rises up and forms clouds after cooling down at higher altitudes.
- Cloud Formation leads to precipitation. This is the reason why ITCZ region is famous for regular rainfall.
- ITCZ region is also famous for immense tropical cyclones and floods.
WHY IS ITCZ THE HOTTEST INSTEAD OF THE EQUATOR?
- You must be wondering that the Equator should be the hottest region. But instead, it is the ITCZ which is the hottest throughout the year.
- Equator is hottest when the ITCZ is above the equator (during Equinox).
- This is because the ITCZ shifts throughout the year depending upon the Earth’s revolution around the sun and its axis tilt (23.5 degrees).
- Equator has the maximum average temperature throughout the year. But, the ITCZ has the highest (peak) temperature at any given time of the year.
HOW DOES THE ITCZ FORM?
- The ITCZ forms due to these 2 reasons:
- Earth’s Axis is tilted (23.5°)
- Earth’s revolution around the sun.
- During summer solstice of the Northern Hemisphere, 23.5° North latitude (Tropic of Cancer) is the closest to the sun due to the 23.5° tilt. Hence, it receives the maximum heat of insolation leading to a very low pressure. This leads to the formation of the ITCZ above the Tropic of Cancer during Summer Solstice of the Northern Hemisphere.
- Similarly, during the Winter Solstice of the Northern Hemisphere, the 23.5° South latitude (Tropic of Capricorn) is closest to the sun and hence, it receives the maximum heat of insolation leading to a very low pressure. This leads to the formation of the ITCZ above the Tropic of Capricorn during Winter Solstice of the Northern Hemisphere.
- This means that the ITCZ follows the low pressure and shifts towards the north of the equator and then to the south completing a 1-year cycle.
EXTENT OF ITCZ
- The ITCZ is not a fixed imaginary line. It does not follow a fixed latitude while shiting.
- Since the landform is not uniform in the northern and southern hemispheres. Hence, low pressure fluctuates due different suface temperature and does not follow a fixed latitude. This leads to the fluctuation of the ITCZ too.
- Maximum extent in Northern Hemisphere: 25°
- Maximum extent in Southern Hemisphere: 20° (due to huge oceans, the surface temperature gets normalized)
- ITCZ forming over the Northern part of India plays a huge role in Indian Monsoon.