GEO 211 1st Edition Lecture 21 Outline of Last Lecture I Air pressure force exerted by the weight of air above a given point A Pressure measurements a Units used on weather maps B Standard atmospheric pressure at sea level 1013 25 mb 1013 25 hPa 29 92 in Hg 760 mm Hg High pressure Low pressure Wind C Measuring pressure A Barometers 1 Mercury barometers 2 Aneroid barometers Altimeter Barograph B Air pressure and altitude decreased rapidly with altitude first but decreases slowly with altitude alof Outline of Current Lecture II Air Pressure continued A Horizontal Pressure Variations influenced by Air temperature Air moisture Air flow movement B Forces that influence wind Pressure gradient force Coriolis force Friction force C Pressure Gradient Force Force that arises from changes in pressure over distance o Shown on weather maps by spacing of isobars Isobars line on a map conveying places with the atmospheric pressure These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Widely spaced isobars indicate gentle gradient stronger winds Closely spaced isobars indicate steeper gradient stronger winds Pressure gradient force generates wind D Coriolis force deflective force resulting from Earth s rotation a How Coriolis force deflects wind Deflection is to the right in the northern hemisphere and to the lef in the southern hemisphere Deflection is absent at the equator but increases with latitude pressure The deflection is more when wind speed is greater Coriolis force doesn t influence wind speed E Friction force resistive force caused by wind blowing over Earth s surfaces F Upper level winds blow parallel to isobars called geostrophic winds A cyclone has low pressure center Anticyclones have high pressure center
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