Winds

11. Consider the following statements about Roaring Forties : 1. They ar

Consider the following statements about Roaring Forties :

  • 1. They are strong Westerly winds found in the oceans of Southern Hemisphere.
  • 2. The strong east to west air currents are caused by the combination of air being displaced from the Equator towards the South Pole and the earth’s rotation and abundance of landmasses to serve as wind breaks.

Which of the statements given above is/are correct ?

1 only
2 only
Both 1 and 2
Neither 1 nor 2
This question was previously asked in
UPSC NDA-1 – 2018
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Statement 1 is correct. The Roaring Forties are strong westerly winds found in the Southern Hemisphere, predominantly over the oceans between approximately 40°S and 50°S latitude.
– Westerly winds blow from west to east.
– The strength of the Roaring Forties is due to the large temperature gradient between the pole and the equator, the Coriolis effect, and importantly, the relative absence of large landmasses in the Southern Hemisphere at these latitudes, which allows winds to circulate with less interruption.
Statement 2 is incorrect because the winds blow from west to east (Westerly), not east to west. Also, the *absence* of significant landmasses in the Southern Hemisphere is crucial to their strength, as landmasses would act as wind breaks, reducing wind speed.

12. Very strong air currents in the upper air westerlies are known as:

Very strong air currents in the upper air westerlies are known as:

Jet streams
Tornados
Blizzards
Chinook winds
This question was previously asked in
UPSC Geoscientist – 2021
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Very strong, narrow air currents in the upper atmosphere, particularly in the westerlies, are known as jet streams.
Jet streams are high-altitude, fast-flowing air currents found at the boundary between different air masses.
The main jet streams are the polar jet and the subtropical jet. They significantly influence weather patterns and the movement of air masses.

13. The Fujita Intensity Scale, developed by late T. Theodore Fujita (Univ

The Fujita Intensity Scale, developed by late T. Theodore Fujita (University of Chicago) is used for measuring the intensity of:

Earthquakes
Rainfall
Tornadoes
Volcanic eruptions
This question was previously asked in
UPSC Geoscientist – 2021
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The Fujita Scale, developed by T. Theodore Fujita, is a scale used to classify the intensity of tornadoes based on the damage they cause. It was later superseded by the Enhanced Fujita Scale (EF-Scale).
The question specifically mentions the scale developed by T. Theodore Fujita for measuring intensity.
Earthquakes are measured using scales like the Richter or Moment Magnitude scale. Rainfall is measured in units of depth. Volcanic eruptions are measured using the Volcanic Explosivity Index (VEI).

14. Which one of the following statements with regard to Jet stream, an up

Which one of the following statements with regard to Jet stream, an upper level tropospheric wave, is not correct?

It is a narrow band of high-velocity wind.
It follows the wave path near the tropopause at elevations of 8 km to 15 km.
Jet streams are typically continuous over long distances.
In summer, the polar front jet achieves its maximum force.
This question was previously asked in
UPSC CDS-1 – 2017
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Statement D is incorrect. The polar front jet stream is strongest during the winter season in each hemisphere. This is because the temperature gradient between the polar regions and the mid-latitudes is steepest in winter, providing the maximum energy difference to drive the high-velocity winds of the jet stream. In summer, the temperature gradient weakens, and the jet stream becomes weaker and typically shifts poleward.
Jet streams are fast-flowing, narrow air currents found in the upper atmosphere (tropopause and lower stratosphere) at altitudes of 8 to 15 kilometers (Statement B). They are characterized as narrow bands of high-velocity winds (Statement A) and extend continuously over long distances around the globe, although their path meanders in wavelike patterns (Statement C).
The polar front jet stream is a major factor influencing weather patterns in the mid-latitudes, guiding the path of storm systems. The other major jet stream is the subtropical jet, found closer to the tropics, which is also stronger in winter.

15. Which one of the following is the reason due to which the wind in the

Which one of the following is the reason due to which the wind in the southern hemisphere is deflected towards its left ?

Difference in the water masses of northern and southern hemisphere
Temperature and pressure variations
Inclined axis of the Earth
Rotation of the Earth
This question was previously asked in
UPSC CDS-1 – 2016
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The wind in the southern hemisphere is deflected towards its left due to the rotation of the Earth.
The apparent force that causes moving objects (like wind and ocean currents) to be deflected from a straight path on a rotating planet is called the Coriolis effect. The Coriolis force acts perpendicular to the direction of motion. Due to the Earth’s rotation, this deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
The Coriolis effect is zero at the Equator and maximum at the poles. It significantly influences large-scale weather patterns, ocean currents, and the direction of cyclones. Temperature and pressure variations drive the movement of air (wind), but the deflection of that movement is caused by the Earth’s rotation.
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