Q.2: Explain various factors of Monsoon and the variability due to climate

Monsoon is a type of climate in which the general pattern of circulation of atmosphere reverses its direction with change in season. Generally, across the world, the monsoons are experienced in the tropical area roughly between 20° N and 20° S.

Indian monsoon represents true monsoon climate where the reversal in the direction of the wind is almost 180 degree to 120 degree. It includes special features like

• ‘rain bearing system’,
• ‘burst of monsoon’,
• ‘gradual extension’,
• ‘breaks of Indian monsoon’
• and ‘gradual retreating’.

Factors of Indian Monsoon:

• The differential heating and cooling of land and water creates a low pressure on the landmass of India while the seas around experience comparatively high pressure.
• The shift of the position of Inter Tropical Convergence Zone (ITCZ) in summer, over the Ganga plain (this is the equatorial trough normally positioned about 5°N of the equator. It is also known as the monsoon-trough during the monsoon season).
• The presence of the high-pressure area, east of Madagascar, approximately at 20°S over the Indian Ocean. The intensity and position of this high-pressure area affect the Indian Monsoon.
• The Tibetan plateau gets intensely heated during summer, which results in strong vertical air currents and the formation of low pressure over the plateau at about 9 km above sea level.
• The movement of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer.

Climate Change impact on Monsoon:

Climate Change is a change in global or regional climate patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels. It affects the Indian Monsoon in two ways i.e.

1. Change in frequency of monsoon
2. Change in intensity of monsoon

Change in both frequency and intensity of monsoon leads to

According to the World Bank, a decline in monsoon rainfall since the 1950s has already been observed. The frequency of heavy rainfall events has also increased.

• A 2°C rise in the world’s average temperatures will make India’s summer monsoon highly unpredictable.
• At 4°C warming, an extremely wet monsoon that currently has a chance of occurring only once in 100 years is projected to occur every 10 years by the end of the century.
• An abrupt change in the monsoon could precipitate a major crisis, triggering more frequent droughts as well as greater flooding in large parts of India.
• India’s northwest coast to the south eastern coastal region could see higher than average rainfall.
• Dry years are expected to be drier and wet years wetter.