SOUTHWEST MONSOON

Characteristics:

• Prevailing Westerlies: These winds are predominant in the mid-latitudes (between 30 and 60 degrees north and south of the equator). They blow from the subtropical high-pressure belts towards the poles.
• Jet Streams: High-altitude westerly winds known as jet streams are important in influencing weather patterns and the movement of weather systems across the globe. They are fast flowing and occur in the upper levels of the atmosphere.
• Polar Front: In the mid-latitudes, the westerlies interact with polar easterlies near the polar front, leading to the development of extratropical cyclones and storms

Monsoons in India occur due to seasonal changes in wind patterns and temperature differences between land and sea.

Here's a concise explanation of the process:

• Differential heating: During summer, the Indian landmass heats up more quickly than the surrounding Indian Ocean.
• Low pressure system: The heated land creates a low-pressure area over the Indian subcontinent.
• Wind direction shift: This low pressure draws in moisture-laden winds from the cooler Indian Ocean towards the land.
• Orographic lift: As these winds encounter geographical features like the Western Ghats or the Himalayas, they are forced to rise.
• Condensation and precipitation: The rising air cools, causing water vapor to condense and form clouds, leading to heavy rainfall.
• Duration: This pattern typically lasts from June to September, bringing the majority of India's annual rainfall.

• The primary driver is the temperature difference between the land and the surrounding sea. During summer, the land heats up faster than the ocean, creating a low-pressure area over the land and a high-pressure area over the ocean. This pressure difference leads to the movement of moist air from the ocean to the land
• Warm sea surface temperatures are crucial as they increase the evaporation rate, contributing to the formation of moist air masses that drive the monsoon rains.
• The monsoon winds, which are part of the larger atmospheric circulation, shift according to the seasonal temperature differences. The southwest monsoon, for instance, is driven by the southwest winds that carry moisture from the Indian Ocean to the Indian subcontinent.
• The geographical features, such as mountain ranges, play a significant role. For example, the Western Ghats in India force moist air to rise, cool, and condense, leading to heavy rainfall on the windward side
• The movement and strength of the high-pressure systems over the oceans and low-pressure systems over the land influence the intensity and timing of the monsoon.
• Phenomena such as El Niño and La Niña can affect the strength and timing of the monsoon. For example, El Niño can lead to weaker monsoons due to altered wind patterns and sea surface temperatures

• El Niño is generally associated with a weaker Indian monsoon. The warming of the central and eastern Pacific Ocean during El Niño tends to disrupt the normal atmospheric circulation patterns, leading to reduced rainfall over the Indian subcontinent.
• The onset of the monsoon can be delayed, and the overall intensity of the rainfall during the monsoon season might be lower than usual
•  El Niño often brings drier conditions to Southeast Asia and northern Australia, leading to droughts and reduced rainfall
• Eastern and southern Africa may experience drier conditions as well

• La Niña, characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, is typically associated with a stronger Indian monsoon. It often leads to increased rainfall over the Indian subcontinent
• The enhanced monsoon can lead to heavier rains and potentially more frequent and intense flooding
• La Niña tends to bring wetter conditions to Southeast Asia and northern Australia, potentially causing heavy rains and flooding
• La Niña can lead to wetter conditions in parts of northern South America