What is a monsoon low? Describe how it influences the monsoon system.
A monsoon low is a low-pressure area that forms over the Indian subcontinent, particularly over northwestern India and the adjoining regions during the summer months (June–September). It plays a vital role in controlling the intensity, distribution, and progression of the Southwest Monsoon.
What is a Monsoon Low?
- A monsoon low (also called monsoon depression when intensified) is a mesoscale synoptic system.
- It forms due to intense solar heating over the Indian landmass, especially the Thar Desert, which becomes significantly hotter than the surrounding oceans.
- This leads to convection and the uplift of air, creating a low-pressure center near the surface.
Influence of Monsoon Low on Monsoon System:
- Drives Moisture-Laden Winds from Ocean:
- The monsoon low acts like a vacuum, pulling in moist southwesterly winds from the Arabian Sea and Bay of Bengal toward the land.
- These winds bring copious rainfall when they encounter the Western Ghats or the Himalayas.
- Steers Monsoon Depressions:
- The low-pressure zone helps in guiding the monsoon depressions, especially those originating in the Bay of Bengal.
- These depressions move northwestward and provide widespread and prolonged rainfall in central and northern India.
- Controls Monsoon Trough Position:
- The monsoon trough (a belt of low pressure) oscillates around the monsoon low.
- When the trough is near the foothills of the Himalayas, rainfall shifts to northern India and Nepal.
- When it is southward, central and peninsular India receive more rain.
- Affects Rainfall Distribution and Intensity:
- The strength and persistence of the monsoon low determine whether the monsoon will be active or break.
- A deep and well-established monsoon low results in active monsoon phases with widespread rain.
- If the low weakens or shifts, it leads to break monsoon conditions, especially over northwest India.
- Impact on Agriculture and Economy:
- Since monsoon rains feed rivers and support agriculture, the presence of a strong monsoon low is critical for crop production.
- Delays or weaknesses in the low-pressure formation can lead to droughts or floods, severely affecting rural livelihoods.