UPSC Prelims 2020 Question:

Consider the following statements

1. Jet streams occur in the Northern Hemisphere only. 
2. Only some cyclones develop an eye. 
3. The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.
   
   

Which of the statements given above is/are correct?

Explanation:

• Jet streams are relatively narrow bands of high-velocity wind in the upper atmosphere. They blow from west to east, but the flow frequently shifts to the north and south. They are formed by the separation of hot and cold air. Since these hot and cold air boundaries are most pronounced in the winter, jet streams are strongest in both the Northern and Southern Hemispheres. So, statement 1 is not correct.
  
  
• The ‘eye’ of a tropical cyclone is a roughly circular area of comparatively light winds and fair weather found at the centre of a severe tropical cyclone. The eye is the region of lowest surface pressure and warmest temperatures aloft (in the upper levels). An eye will usually develop when the maximum sustained wind speeds go above 74 mph (119 km/h). So, statement 2 is correct.
  
  
• The eye temperature may be 10°C warmer or more at an altitude of 12 km than the surrounding environment, but only 0-2°C warmer at the surface in the tropical cyclone (Hawkins and Rubsam 1968). So, statement 3 is not correct.
  
  

Therefore, option (3) is the correct answer.

Subject: Geography | Climate Weather and Atmosphere