Geostrophic wind is a crucial concept in meteorology that describes the horizontal wind velocity in the upper atmosphere under the influence of the balance between the pressure gradient force and the Coriolis effect. In simpler terms, it is the wind that results from a balance between the pressure gradient force, which is the force that causes air to move from high to low-pressure areas, and the Coriolis effect, which is the apparent deflection of moving air caused by the Earth’s rotation. The relationship between barometric slope and air circulation is integral to understanding geostrophic wind. Barometric slope refers to the variation in atmospheric pressure over a given distance. This pressure difference creates a force that drives air movement, and when in balance with the Coriolis effect, it gives rise to the geostrophic wind, influencing large-scale weather patterns and circulation systems on Earth. Exploring this relationship enhances our comprehension of atmospheric dynamics and contributes to accurate weather forecasting.
Answer
The air blowing above the ground or water surfaces, generally between the altitudes of 500- 1000 mt, parallel to the isobars and at the right angle to the pressure gradient, is called Geostrophic wind. Ex- Jet streams, Rossby waves, Upper tropospheric westerlies. etc
Relationship between barometric slope and air circulation.
- Air movement follows a barometric slope: It depends on the steepness of gradients
- a. E.g.- The steeper the pressure gradient, the higher the rate of air movement (wind speed) and vice versa.
- Steepness in barometric slope and with conditions of low friction increase the air movement. With approaching distance, it gets deflected due to strong Coriolis force and wind crosses the isobars at an acute angle along latitude
- a. E.g.- Upper tropospheric westerlies, Jet stream
- Frictional force works in opposition to the barometric slope and hence against the horizontal movement of air. It reduces the wind speed(velocity) and Coriolis effect, thus it leads to
- a. E.g.- Formation of thunderstorms and local winds.
- Gradient winds: Barometric slope, Coriolis force, centripetal force, and frictional force result in gradient winds.
- a. E.g.- cyclonic conditions are also known as Subgeostrophic winds where centripetal force strengthens PGF countering Coriolis force.
- b. E.g.- Anticyclonic Conditions are also known as Supergeostrophic winds where centripetal force strengthens the Coriolis force countering PGF.
However, in recent days because of climate change, the barometric slope and the pressure gradient between latitudes are rapidly changing impacting upper tropospheric wind, weakening of polar vortex impacting the weather of mid-latitude like bomb cyclone, heat waves of Europe, omega blocking of Canada.
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