GEO 155 1st Edition Lecture 6 Outline of Last Lecture I Global Energy Balance Outline of Current Lecture I Atmospheric Forces and Motion a Gradient Winds Alof b Friction and Surface Winds c Cyclones and Anticyclones II General Circulation of the Atmosphere a Pressure and Winds on a Smooth Uniform Earth i At Low Latitudes Current Lecture Atmospheric Forces and Motion Winds Alof In the Northern Hemisphere Coriolis deflects wind so far to the right that moves parallel to isobars o Wind moves very fast due to the Coriolis Effect o Known as gradient wind or geostrophic wind Here pressure gradient force moves from high to low pressure Point of Reference When determining the direction of Coriolis always remember that your point of reference is standing with your back facing towards the wind That is in a gradient wind the pressure gradient force moves from high pressure to low pressure Thus one would stand with his or her back facing toward the high pressure gradient so that Coriolis would deflect wind to the right in the Northern Hemisphere Friction Due to friction at the Earth s surface winds move slower closer to the surface o Winds are not deflected as strongly near the surface as compared to geostrophic wind 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 Rather than being deflected parallel to the isobars wind deflects at an acute angle to the isobars In the Northern Hemisphere winds deflect to the right when facing away from the wind Cyclones and Anticyclones Low Central Pressure Cyclonic circulation Winds spiral into the low pressure center In the Northern Hemisphere Coriolis deflects the wind to the right at an acute angle in all directions of the pressure gradient force which pushes inward from high to low pressure In the Southern Hemisphere Coriolis deflects the wind to the lef at an acute angle in all directions of the pressure gradient force which lies perpendicular to the low pressure center in four directions High Central Pressure Anti cyclonic circulation Pressure gradient force pushes outward In the Northern Hemisphere wind blows right In the Southern Hemisphere wind blows lef General Circulation of the Atmosphere Pressure and Winds on a Smooth Uniform Earth During Equinox Equator receives most solar radiation due to solar beaming o Air heats up and rises Atmospheric pressure decreases equatorial low pressure Air reaches tropopause then moves back to the surface o Also known as the Inter tropical Convergence Zone ITCZ and the Doldrums where winds converge from the subtropics and blow horizontally Air reaches surface again at higher latitudes 30 degrees north and south of the equator Horse Latitudes o Sub tropic High Pressure STH creates a pressure gradient force Wind deflected towards equator from high pressure areas NOTE Winds are always named afer the direction in which they flow from Winds from STH known as Easterly Trade Winds o Northeasterly Wind winds from 30 degrees North o Southeasterly Wind winds from 30 degrees South Air sinks back to the equator o Hadley cells vertical cross section of the atmospheric pressure changes Air rises moves to sub tropic highs sinks back to surface and returns to ITCZ
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