Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
707 views
in Air Pressure Belts and Winds by (58.5k points)
closed by

Perform a scientific analysis of the principles related to the origin of monsoon winds.

1 Answer

+1 vote
by (42.9k points)
selected by
 
Best answer

The word monsoon is derived from the Arabic word ‘Mausim’, which means weather. Therefore, monsoon winds are those winds that change their direction according to the weather. 

The following concepts are proposed for the origin of these winds:

1. Thermal Concept: According to this theory, the origin of monsoon is due to the uneven organization of the earth (terrestrial and aquatic part) and due its opposing nature of heating up and cooling down. Due to more insolation in summer, areas of low pressure tend to form in land areas which become more heated up in comparison, due to which the winds move from the sea areas towards the land areas. This is called Summer Monsoon.

On the contrary, in the winter, due to the southward movement of the Sun, terrestrial parts become the centers of high pressure and the sea parts become the centers of low pressure. As a result, the winds blow from the terrestrial part to the oceans, which are called winter monsoons. These are also called the north – eastern monsoon.

2. Motion Concept: Flon reaffirmed the concept of dynamic origin by refuting the thermal origin of monsoon. According to him, the origin of monsoon winds is due to the air pressure and the shifting of the air belts. Convergence occurs due to the conjunction of trade winds near the equator. This is called tropical convergence zone. Its northern, boundary is called NITC and the southern boundary is called SITC. This ITC has a belt of Doldrum, in between, in which the equatorial ‘Westerlies winds’ blow.

At the time of Summer solstice, the NITC shifts and extends up to 30° North Latitude, which includes South East Asia. Therefore, the doldrum’s equatorial linear westerly winds are established on these parts, which are the southwest monsoon winds of the summer. Similarly, when the motion of the sun is towards the south, NITC shifts from south – east Asia and the north – east trade winds are restored in it. This is the northern – eastern monsoon.

3. Modern Concept: It is also known as the ‘jet stream’ concept. In southern Asia, this jet stream flows from east to west in rapid form in the troposphere, at an altitude of approximately 12 km. from the west towards the east. It is called sub – tropical westerlies jet stream here. Its altitude is 9 to 10 km. at 60° North latitude and its height is low on the poles.

In the northern hemisphere, this high – level westerly jet stream is split due to the mechanical obstruction of Himalayas and the Tibet Plateau during winter. Its northern branch flows from west to east in the north of Tibetan Plateau (in crescent form) and its main branch flows from west to east in the south of Tibetan Plateau and the Himalayas.

The main branch follows the cyclonic route through the top of Afghanistan and Pakistan. The effect of this is the creation of the autumnal monsoon. In the summer, after March 21, the motion of the sun becomes northwards, due to which polar surface high air pressure becomes weak. Due to the north of the high level polar vortex, towards the north, the high level westerly shift jet stream also shifts towards north.

This jet stream completely disappears from India by mid – June. Now Jet Stream flows in the opposite direction of the winter route north of the Tibetan Plateau. The flow of this high coastal jet stream over the northern part of Iran and Afghanistan is in the form of a cyclonic curve (in the opposite direction of the clock needle), resulting in dynamic downturn and cyclonic condition in the troposphere.

This high level low pressure extends to north – western India and Pakistan. Below this, the thermal low pressure is already developed on the land. Due to this situation, the winds rise above the surface pressure and high level low pressure pulls these winds upwards, due to which sudden burst of south – west monsoon is observed.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...