Geography - 3 | Current Affairs & Hindu Analysis: Daily, Weekly & Monthly - UPSC PDF Download

Cyclone Mocha

Context

The India Meteorological Department (IMD) recently issued a bulletin forecasting that cyclone Mocha is expected to intensify into a severe storm.

• About Cyclone Mocha:
• It is a tropical cyclone formed over the southern Bay of Bengal.
• The cyclone's name ‘Mocha’ is suggested by Yemen and was named after the Red Sea port city, which is known to have introduced coffee to the world.
• How a Tropical Cyclone Formed?
  • A tropical cyclone is formed only over warm ocean waters near the equator.
  • Warm, moist air rises up and away from the ocean surface, creating an area of low pressure.
  • It causes the air from surrounding areas with higher pressure to move towards the low-pressure area.
  • This leads to the warming up of air and causes it to rise above.
  • As the air rises & cools, the water in the air forms clouds.
  • This complete system of clouds and wind spins & grows, along with the ocean’s heat.
  • As the wind rotation speed increases, an eye gets formed in the middle.
• Characteristics of a Tropical Cyclone:
  • The centre of a cyclone is very calm and clear with very low air pressure.
  • The average speed is 120 kmph.
  • They have closed isobars which leads to greater velocity. Isobars are imaginary lines on a weather map that connect locations with equal atmospheric pressure.
  • They develop over oceans and seas only.
  • They move from east to west under the influence of trade winds.
  • They are seasonal in nature.
• How are Cyclones Classified? Cyclones are classified on the basis of wind speed by the Indian Meteorological Department (IMD):
  • Depression: Wind speeds of between 31–49 km/h
  • Deep Depression: Between 50-61 km/h
  • Cyclonic Storm: Between 62–88 km/h
  • Severe Cyclonic Storm: Between 89-117 Km/h
  • Very Severe Cyclonic Storm: Between 118-166 Km/h
  • Extremely Severe Cyclonic Storm: Between 166-221 Km/h
  • Super Cyclonic Storm: Above 222 Km/h

The Palghat Gap

Context

The article discusses the Palghat (Palakkad) Gap, a significant corridor in the Western Ghats of India. It provides information about the geological origin of the gap.

What is Palghat Gap?

• The Palghat Gap is a 40 km wide corridor in the Western Ghats, known for its steep hills and serving as a gateway to Kerala.
• It is a crucial passage for roads and railways connecting Coimbatore and Palakkad.
• The Bharathappuzha River flows through the Palghat Gap.
• The vegetation in the gap is classified as dry evergreen forest, different from the tropical rainforests of the Western Ghats.
• The Palghat Gap marks a distinct divide in the flora and fauna of the region.

Geological origin of the Palghat Gap

• The Palghat Gap is a geological shear zone running from east to west.
• Shear zones are weak regions in the Earth’s crust, occasionally causing tremors in the Coimbatore region.
• The formation of the Palghat Gap occurred when the continental shelves shifted after the separation of Australia and Africa from the Gondwana landmass.
• India and Madagascar were connected until volcanic activity led to their split, with a similar gap called the Ranotsara Gap in Madagascar.

Biogeographic distinctions and ancient history

• The biogeographic distinctions in species north and south of the Palghat Gap may be attributed to an ancient river or an incursion of the sea in the distant past.
• Elephant populations on the Nilgiris side of the gap have different mitochondrial DNA from elephants in the Anamalai and Periyar sanctuaries.
• DNA analysis of the White-bellied Shortwing, an endemic bird species, shows divergence between populations in the Nilgiris and the Anamalai regions.

Biodiversity south of the Palghat Gap

• The southern region of the Western Ghats, located south of the Palghat Gap, exhibits high species richness and phylogenetic diversity.
• A recent study reports over 450 tree species, including ancient species like Magnolia champaca, dating back 130 million years.
• The warm weather and moist air of the southern Western Ghats support a diverse range of life, making it an island refuge during cycles of ice ages and droughts.
• The southern Western Ghats receive rainfall more evenly throughout the year compared to the northern region.

Son River 

Context

The National Green Tribunal (NGT) has issued a directive to halt all mining activities in Son riverbed in Sonbhadra district, Uttar Pradesh.

• The directive addresses illegal mining, imposing environmental compensation on mining companies.

What are the Characteristics of Son River?

• About:
  • The Son River, also known as the Sone River, is a perennial river that flows through central India.
  • The Son River is the 2^nd-largest southern (right bank) tributary of the Ganges after the Yamuna River.
• Geography:
  • It originates near Amarkantak Hill in the Gaurela-Pendra-Marwahi district of Chhattisgarh and finally merges with the Ganges River near Patna in Bihar.
    • Son forms a series of waterfalls at the edge of Amarkantak plateau.
  • It flows through four states: Chhattisgarh, Madhya Pradesh, Uttar Pradesh, and Bihar.
• Tributaries:
  • Ghaghar, Johilla, Chhoti Mahanadi, Banas, Gopad, Rihand, Kanhar and North Koel River.
• Prominent Dams and Hydroelectric Projects:
  • Bansagar Dam in Madhya Pradesh
  • Rihand Dam near Pipri in Uttar Pradesh on Rihand River.
  • Indrapuri Barrage in Bihar; it diverts water from the Son River to the Sone Canal System for irrigation purposes.
  • Koilwar Bridge constructed in 1862 in Bihar; it serves as India's oldest river bridge, connecting Arrah with Patna.

Indian Ocean Dipole 

Context

The Indian Monsoon is expected to be influenced by the El Nino phenomenon in 2023, there are also anticipations of a positive Indian Ocean Dipole (IOD) developing, which could potentially offset the impact of El Nino.

• According to the India Meteorological Department (IMD), there is about 80% probability for positive IOD conditions and 15% of a neutral IOD during June-August 2023 season.
• While the El Nino is already firmly established in the Pacific Ocean in 2023, the IOD is still in the neutral phase and may develop in the coming months.

What is the Indian Ocean Dipole (IOD)?

• IOD or Indian Nino:
  • IOD, sometimes referred to as the Indian Nino, is similar to the El Nino phenomenon, occurring in the relatively smaller area of the Indian Ocean between the Indonesian and Malaysian coastline in the east and the African coastline near Somalia in the west.
    • The El Nino is the warmer-than-normal phase of the El Nino Southern Oscillation (ENSO) phenomenon, during which there are generally warmer temperatures and less rainfall than normal in many regions of the world, including India.
  • One side of the ocean, along the equator, gets warmer than the other.
  • IOD is said to be positive when the western side of the Indian Ocean, near the Somalia coast, becomes warmer than the eastern Indian Ocean.
  • It is negative when the western Indian Ocean is cooler.
• Mechanism:
  • Negative IOD:
  • The air circulation in the Indian Ocean basin moves from west to east, that is from the African coast towards the Indonesian islands, near the surface, and in the opposite direction at the upper levels. That means the surface waters in the Indian Ocean get pushed from west to east.
    • In a normal year, warmer waters in the western Pacific near Indonesia cross over into the Indian Ocean and make that part of the Indian Ocean slightly warmer. That causes the air to rise and helps the prevailing air circulation.
  • In the years when the air circulation becomes stronger, more warm surface waters from the African coast are pushed towards the Indonesian islands, making that region warmer than usual. This causes hotter air to rise, and the cycle reinforces itself.
  • This is the state of negative IOD.
• Positive IOD:
  • Air circulation becomes slightly weaker than normal. In some rare cases, the air circulation even reverses direction. The consequence is that the African coast becomes warmer while the Indonesian coastline gets cooler.
    • A positive IOD event is often seen developing at times of an El Nino, while a negative IOD is sometimes associated with La Nina.
  • During El Nino, the Pacific side of Indonesia is cooler than normal because of which the Indian Ocean side also gets cooler. That helps the development of a positive IOD.
• Impact of IOD:
  • In the Indian Ocean, IOD exhibits an ocean-atmosphere interaction that closely resembles the fluctuations observed during El Niño events in the Pacific Ocean. However, the IOD is considerably less powerful compared to El Niño, resulting in relatively minimal impacts.
  • A positive IOD helps rainfall along the African coastline and also over the Indian sub-continent while suppressing rainfall over Indonesia, southeast Asia and Australia. The impacts are opposite during a negative IOD event.
• Past Events:
  • In 2019 the IOD event developed during the late monsoon but was so strong that it compensated for the deficit rainfall during the first month of the monsoon season (June had 30% deficiency that year).
    • The deficit in June that year was also attributed to a developing El Nino but that fizzled out later.

What is ENSO?

• In a normal year, the eastern side of the Pacific Ocean, near the northwestern coast of South America, is cooler than the western side near the islands of Philippines and Indonesia.
  • This happens because the prevailing wind systems that move from east to west sweep the warmer surface waters towards the Indonesian coast.
• The relatively cooler waters from below come up to replace the displaced water.
• An El Nino event is the result of a weakening of wind systems that leads to lesser displacement of warmer waters.
• This results in the eastern side of the Pacific becoming warmer than usual. During La Nina, the opposite happens.
• Both these conditions, together called El Nino Southern Oscillation (ENSO), affect weather events across the world.
• Over India, the El Nino has the impact of suppressing monsoon rainfall.