- Karnataka More rain than MH/Kerala?
- Tibetan plateau: Meteorological importance of
- Natural aerosol and their effect on Monsoon
Topic in news Oct. 2014, Hindu; Relevance: GS1-Geography
Mains-GS1 Q. Examine the reasons why Western ghats in Karnataka receive more rainfall than Maharashtra and Kerala, during Monsoon? 200 words.
Ans: #1: More than Maharashtra because:
- Karnataka’s Mountain topography broader than Maharashtra. Since Mountain width greater => Rain clouds need to travel longer distance => more time for water to coalesce and precipitate as rainfall.
- Compared to this, Narrower width of W.Ghats in Maharashtra=> Rain bearing winds cross over to the leeward side quickly before rainfall can occur.
#2: More than Kerala because:
In Kerala, W.Ghats = isolated mountains. Rain-bearing winds can easily cross over leeward side through the gaps, without precipitation occurring.
#3: Other reasons:
- Karnataka Mountains = gentle slope than Kerala and Maharashtra. Gentle slope= Air parcel can retain energy and speed for a long time, allowing cloud droplets to grow and precipitate as rainfall.
- In Karnataka, mountains are continuous. No gaps= Clouds can’t easily escape to leeward side.
Topic in news Oct. 2014, Hindu; Relevance: GS1-Geography.
- Tibet is the largest and highest plateau in the world.
- Given its altitude and topography, Tibet gets more sunlight, becomes hotter than land at sea level.
- This heating of Tibetan plateau leads to following events
#1: Traditional thermal theory
- Hot Tibetan surface: Increases land-ocean temperature differences, causes pressure gradients.
- Low pressure around Tibet, NW India and Pakistan=> attracts trade winds from Southern hemisphere
- These winds pickup moisture from ocean surface=> finally burst of Monsoon.
#2: Jet stream theory
- Hot Tibetan surface=> intense low Pressure => air pumped upwards in the upper troposphere.
- This air travels southwards and descends at Mascarene High basin near horn of Africa through Tropical Easterly jet (TEJ) stream.
- Surface air from Mascarene High move towards ITCZ (low pressure) developed in North India =>monsoon.
Sidenote: Tibetan plateaus is also called third pole, because of third-largest ice-stock the world. Heavy winter snow on Tibetan plateaus increases surface albedo. It retards spring warming and delays summer monsoon over Northern India.
Yes, but Why in News?
- Despite its meteorological significance, very few weather stations in Tibet, because of its remoteness, altitude and harsh conditions.
- But China Meteorological Administration began putting temperature and moisture detectors, and sensor-towers to measure cloud properties. (Aug 2014)
- This data will understanding relation between land surface heating, its impact on rainfall, snow cover and vegetation changes.
Mains-GS1: Discuss the meteorological importance of Tibetan plateau in 200 words.
Topic in news: March, 2014; Relevance: MCQ about examples of aerosols and scientific principle behind their role in monsoon:
- Aerosols: tiny particles of either soli/liquid, suspended in atmosphere.
- Natural aerosols: sea-salt, water vapour, dust, ash from volcanoes, organic material: spores, bacteria, pollen.
- Artificial aerosols: particles of pollutants like, smoke, ashes.
How aerosols effect rain fall?
- Dust absorbs sunlight and heats the atmosphere=> low pressure condition over land.
- These pockets of low pressure attract south-west monsoon winds into the region.
- Scientists found that dust from West Asia to India=>helps in monsoon.
- IF more dust particles from W.Asia and N.Africa blow towards India, then more rain to India.