Question

What are Jet streams? Explain their influence on the climate of India in summer and winter.

Answer 1

Jet streams are fast blowing air currents of a steady velocity moving in a narrow zone of the troposphere. The Western
Disturbances and the South-West Monsoons are influenced by these jet streams.

Jet streams affect the climate of India. They help in bringing the Western Disturbances to north and north-western parts of India. Western Disturbances cause much needed winter rains over the north and north-westem parts of India and snowfall in the mountains. Though the total amount of winter rainfall “mahawat” is small, they are of great importance for the cultivation of ‘rabi’ crops.

Answer 2

Jet streams are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. A number of separate jet streams have been identified. The most constant are the mid-latitude and the sub tropical jet stream.

Over India, these jet streams blow south of the Himalayas, all through the year except in summer. The western cyclonic disturbances experienced in the north and northwestern parts of the country are brought in by this westerly flow. In summer, the subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the sun. An easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14°N during the summer months.