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Which of the following is correct regarding geostrophic wind?
  • A
    It blows parallel to straight equidistant isobars.
  • B
    It blows parallel to curved isobars.
  • C
    It blows across the isobars from high to low pressure.
  • D
    It is the wind resulting from the vector sum of gradient wind and surface wind, such that the geostrophic wind normally blows at an angle of 20-45 degrees relative to the isobars.

Refer to figure.

The geostrophic wind blows parallel to straight and equidistant isobars. Wind begins as a flow of air perpendicular to the isobars, initially under the influence of the Pressure Gradient Force PGF (from high to low). As the movement begins, the Coriolis force CF begins to influence the moving air causing it to be deflected to the right of its path in the Northern Hemisphere, and to the left in the Southern Hemisphere. This deflection continues until PGF and CF are opposite and balance each other and the airflow becomes parallel to the isobars – PGF and CF act perpendicular to the airflow direction and opposite to each other.
GEOSTROPHIC WIND:

  • Occurs above the friction layer.
  • Occurs at a latitude greater than 15 degrees.
  • Occurs when the isobars are straight, parallel and equidistant (constant gradient).
Occurs when the pressure situation is not changing rapidly (constant gradient/equidistant).

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