Maharashtra State PSC Model Paper 3

The correct answer is 2 and 3 only.

Important Point

• Jet streams are circumpolar (situated around or inhabiting around one of the earth’s poles), narrow, concentrated bands of meandering, upper tropospheric, high velocity, geostrophic streams, bounded by low-speed winds and are a part of upper-level westerlies. Hence, statement 1 is correct.
  • The direction of the jet stream is determined by pressure gradient force (temperature contrast creates pressure gradients) and Coriolis force.
  • The direction of the jet stream is perpendicular to the pressure gradient force.
• There are two permanent jet streams – subtropical jets at lower latitudes and polar front jets at mid-latitudes. Hence, statement 2 is NOT correct.
• Pressure gradient increases with altitude and creates high-velocity winds at higher altitudes.
  • The friction in the upper troposphere is quite low due to less dense air. Hence the Jet streams flow at great velocities.
  • Temperature also influences the velocity of the jet stream.
    • The greater the difference in air temperature, the faster the jet stream, which can reach speeds of up to 250 mph (402 kph) or greater, but averages about 110 mph (177 kph). Hence statement 3 is NOT correct.
    • The jet streams have an average velocity of 120 kilometres per hour in winter and 50 km per hour in summer.
    • These jet streams also have cores where the speed is much greater.