ITCZ | Inter Tropical Convergence Zone

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.