GEO 211 1st Edition Lecture 21 Outline of Last Lecture I. Air pressure- force exerted by the weight of air above a given pointA. Pressure measurementsa. 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 pressureA. Barometers1. Mercury barometers2. Aneroid barometers- Altimeter BarographB. Air pressure and altitude decreased rapidly with altitude first, but decreases slowly with altitude alofOutline of Current Lecture II. Air Pressure continuedA. Horizontal Pressure Variations influenced by:- Air temperature- Air moisture- Air (flow) movementB. Forces that influence wind:- Pressure gradient force- Coriolis force- Friction forceC. Pressure Gradient Force- Force that arises from changes in pressure over distanceo Shown on weather maps by spacing of isobars- Isobars- line on a map conveying places with the atmospheric pressureThese 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 windD. Coriolis force- deflective force resulting from Earth’s rotationa. 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 speedE. Friction force- resistive force caused by wind blowing over Earth’s surfacesF. Upper level winds- blow parallel to isobars called geostrophic winds- A cyclone has low pressure center- Anticyclones have high pressure
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