DAILY CURRENT AFFAIRS QUIZ – 18 November 2024

Ans. b

Explanation:

The Atlantic Meridional Overturning Circulation (AMOC):

1. Characteristics of AMOC

• Nature of Circulation: AMOC is a part of the broader global ocean conveyor belt, known as Thermo-Haline Circulation (THC), influencing the movement of ocean water due to variations in density caused by temperature and salinity differences. Within the Atlantic Ocean, it encompasses various currents such as the warm Gulf Stream, North Atlantic Drift, and the frigid Southern Ocean current.
• Flow of Warm and Cold Water: AMOC transports warm surface waters from tropical regions toward the Northern Hemisphere, where they cool and sink. Subsequently, this cooled water returns to the tropics and then to the South Atlantic as a lower-level current. From there, it disseminates across all ocean basins via the Antarctic circumpolar current.

2. Correction and Validation of Statements:

• Statement 1 (Incorrect): Contrary to the statement, AMOC, a crucial segment of the global ocean conveyor belt, works to sustain warmer conditions in mid to high latitudes along the eastern coast of America and Western Europe by transporting warm surface waters via the Gulf Stream and North Atlantic Drift.
• Statement 2 (Correct): According to IPCC’s Assessment Report 6 (AR6) and recent articles in Nature Climate Change, human-induced climate change is causing an unprecedented slowdown of the AMOC, attributable to the accelerated melting of Arctic ice shelves, notably in “The Last Ice Area.” This influx of freshwater diminishes water salinity and density, hindering the typical sinking of water and subsequently weakening the AMOC flow.

3. Predicted Implications of AMOC Weakening:

• Projected Consequences: Anticipated impacts of AMOC slowdown include:
  1. Substantially cooler climates in North America and Western Europe.
  2. Reduced rainfall in Europe due to the significant southward migration of rain belts over the tropical Atlantic.
  3. Diminished nutrient transport in the Atlantic Ocean basin, impacting fishing areas like Newfoundland.
  4. Possible influence on El Niño patterns.
  5. Increased sea ice formation over the Greenland-Iceland-Norwegian seas and the southern vicinity of Greenland.

Ans. c

Explanation:

The Inter-Tropical Convergence Zone (ITCZ):

1. Geographical Position and Nature

• Geographical Range: Extending approximately five degrees north and south of the equator, the ITCZ forms a broad belt encircling the Earth.
• Pressure Characteristics: It represents a wide trough of low pressure situated in equatorial latitudes, where the northeast and southeast trade winds converge.

2. ITCZ Movement and Seasonal Impact

• Movement in Relation to the Equator: ITCZ generally aligns parallel to the equator but shifts its position northward or southward following the apparent movement of the sun.
• Seasonal Influence on Rainfall: Shifts in the ITCZ significantly impact rainfall patterns in equatorial regions, leading to distinct wet and dry seasons characteristic of the tropics, different from the cold and warm seasons found in higher latitudes.

3. Comparison of ITCZ Shifts between Hemispheres

• Northern vs. Southern Hemisphere Shifts: The movement of the ITCZ exhibits a lesser shift in the Southern Hemisphere compared to the Northern Hemisphere. This is primarily due to the more continental nature of the Northern Hemisphere, resulting in a sharper temperature gradient.

Ans. d

Explanation:

Winds with Distinct Characteristics:

1. Mistral

• Description: Mistral, a cold and dry powerful wind in southern France, blows from the north along the lower Rhône River valley towards the Mediterranean Sea. It sustains for extended periods, averaging approximately 74 km/h (45 miles/h), primarily prevalent and most forceful in winter, sometimes leading to significant crop damage.

2. Pampero

• Description: Pampero, a cold and dry wind occurring in the Pampas region (Argentina) during winter, results from a burst of cold polar air sweeping westward, southwestward, or southward over the pampas across South American countries like Brazil, Argentina, Uruguay, Paraguay, and Bolivia. Associated with a passing cold front of an active low, it intensifies into a squall line, causing a noticeable temperature drop. In Buenos Aires, these storms during summers serve as a welcomed relief from high humidity and extreme heat.

3. Simoon

• Description: Simoon, a scorching, arid, suffocating, and dust-laden wind, ravages African deserts, notably impacting regions like Arabia, Syria, and neighboring countries. Generated by extreme desert heat, it carries dust and sand, reshaping deserts and sand dunes during late Spring and Summer. Despite its brevity, lasting around 20 minutes, it can result in whirlwinds, predominantly due to low-level thermic heating, significantly impacting desert landscapes.

Ans. a

Explanation:

Characteristics of Hot Deserts:

1. Global Distribution and Positioning

• Desert Coverage: Deserts encompass over one-fifth of the Earth’s landmass, spanning every continent.
• Hot Desert Locations: Hot deserts primarily reside around the Tropics of Cancer and Capricorn, typically between 15° and 30° north or south of the equator.
• Association with Atmospheric Conditions: These deserts align with the Horse Latitudes or Sub-Tropical High-Pressure Belts, where descending air impedes precipitation.

2. Influence of Air Movement and Relative Humidity

• Wind Patterns: Rain-bearing Trade Winds diverge away from deserts, while the on-shore Westerlies stay outside desert limits. The arriving winds, cooler and with reduced humidity, discourage condensation.
• Minimal Cloud and Low Humidity: The skies over deserts remain predominantly clear, with relative humidity plummeting from 60% in coastal regions to less than 30% in desert interiors. This arid environment facilitates constant evaporation, establishing a perpetual state of drought.

3. Rare Precipitation and Local Effects

• Scarce Rainfall: Desert regions experience unreliable and minimal precipitation.
• Effect of Cold Currents: Cold currents along western coasts generate mists and fogs, but as they interact with the warm land, little rainfall occurs. Notably, the Atacama or Peruvian Desert epitomizes extreme aridity with an annual rainfall of fewer than 1.3 cm.

4. Reasons for Tropics Association

• Hadley Cell Explanation: Deserts align with the Tropics due to the Hadley Cell’s atmospheric process, where ascending warm air at the equator leads to heavy rainfall, followed by descending, dry air with elevated temperatures in the tropics.

5. Examples of Major Hot Deserts

• Desert Examples: Notable hot deserts include the expansive Sahara Desert stretching 3,200 miles east to west and approximately 1,000 miles wide. Other significant hot deserts encompass the Great Australian Desert, Arabian Desert, Iranian Desert, Thar Desert, Kalahari Desert, Namib Desert, and various deserts in North and South America, each with unique characteristics and names based on their geographical regions.

Ans. b

Explanation:

Vertical Pressure Gradient and Atmospheric Dynamics:

1. Vertical vs. Horizontal Pressure Gradients

• Vertical Pressure Gradient: Significantly larger than horizontal pressure gradient but typically counterbalanced by an almost equal, opposing gravitational force. As a result, strong upward winds are generally absent.

2. Pressure Variations with Height

• Vertical Pressure Gradient or Variation: In the lower atmosphere, pressure diminishes swiftly with altitude. This vertical pressure variation, often known as the vertical pressure gradient, decreases at an approximate rate of 34 millibars for every 300 meters in height.

3. Pressure-Driven Air Motion

• Cause of Air Motion: Atmospheric pressure variances drive air movement, leading winds to flow from areas of high pressure toward regions of low pressure.

4. Pressure Changes and Weather Indicators

• Weather Indicators: Rising pressure signifies stable, clear weather conditions, while falling pressure indicates potential instability and cloudy weather.

5. Pressure Variability and Altitude

• Altitude and Pressure Relations: At higher elevations, such as at the summit of Mt. Everest, air pressure is significantly lower, approximately two-thirds less than at sea level.
• Variable Factors Affecting Pressure: Pressure decrease with altitude isn’t constant due to changing factors influencing air density—temperature, water vapor content, and gravity. This variability prevents a simple, direct relationship between altitude and pressure.

6. Gravity, Density, and Pressure

• Gravity’s Influence on Pressure: At the surface, denser air due to gravity results in higher pressure. As air pressure is contingent on both density and temperature, alterations in either temperature or density bring about corresponding pressure changes.