GEOG 1290 Lecture Notes - Lecture 6: Atmospheric Pressure, Sea Breeze, Pressure Gradient
14 Apr 2016
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3 forces: pressure gradient, coriolis effect, friction. As the atmosphere is held down by gravity, it exerts a force upon every surface (pressure = force per unit area) At sea level the force is the weight of 1 kg of air that lies above each square centimeter of the surface. Pascal avg sea level pressure (slp) is 101,320 pa. Millibar 1000 mb = 10,000 pa avg slp = 1013. 2 mb. Atmospheric pressure decreases rapidly with altitude near the surface. Therefore a small change in elevation will often produce a significant change in air pressure. Differences in air pressure = a pressure gradient. The pressure gradient forces acts at right angles to the isobars (90 degrees) Defined as air motion with respect to the earth"s surface i. e. , movement is dominantly horizontal. Note: air motion that is dominantly vertical referred to a updrafts and downdrafts. Direction where the wind is coming from.
