Lecture 8 - EFFECTS OF METEOROLOGY February 15th 2011...

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Unformatted text preview: 2/14/11 EFFECTS OF METEOROLOGY February 15th, 2011 GEOG 371 THIS WEEK  Course Changes/Schedule:   Test do-over – Thursday (2/17)   Instrument presentation – Next Tuesday (2/22)   Homework #5 – problems due Next Thursday (2/24)  Meteorology   Many scales   Global   Boundary Layer   Microscale   Stability 1 2/14/11 LIFTING MECHANISMS IN THE ATMOSPHERE  Orographic Lifting  Convergence  Diabatic Heating: Thermals  Frontal Systems HORIZONTAL FORCES ACTING ON THE AIR  Pressure-gradient force  Apparent Coriolis force  Friction force  Apparent Centrifugal force 2 2/14/11 PRESSURE GRADIENT FORCE PER UNIT MASS 100 km PGF = H 1012 mb = 1008 mb 1 "p ! "x L " 1012 ! 1008 mb % 100 kg 1 $ ' & m s 2 mb 1. 2 kg m!3 # 10 5 m = 0.0033 m s-2 APPARENT CORIOLIS FORCE North Pole B B’ CF = 2!V sin " C Direction of Earth’s rotation A West D A’ Equator East E H F F’ E’ G South Pole 3 2/14/11 WINDS  Forces combine to form different types of winds  Geostrophic wind  Surface winds along straight isobars  Gradient Winds  Surface winds along curved isobars GEOSTROPHIC WIND 150 km Apparent Coriolis force Pressure gradient force H Geostrophic wind L Example: Find V when ϕ=30 oN 570 mb 2!V sin " = V= CF = PGF 566 mb 1 $p # $x V= 1 $p !2 " sin # $x 13, 700 s # 570 ! 566 mb& 100 kg m % ( = 50 s 0.73 kg m !3 $ 1.5 " 10 5 m ' m s2 mb 4 2/14/11 SURFACE WINDS ALONG PARALLEL ISOBARS Figure 6.2 CYCLONIC FLOW (NORTH. HEM.) 834 mb Apparent Coriolis force Pressure gradient force Gradient wind 830 mb L Apparent centrifugal force Force Balance V 2 1 $p 2!V sin " + = r # $r r = distance from center of curvature V2/r = Apparent centrifugal force per unit mass = -Centripetal force per unit mass Figure 6.3 5 2/14/11 ANTICYCLONIC FLOW (NORTH. HEM.) 830 mb Apparent Coriolis force Pressure gradient force Gradient wind 834 mb H Apparent centrifugal force Force Balance 2"V sin # = 1 %p V 2 + $ %r r Pressure gradients are weaker and winds are slower around a center of high than around a center of low. Figure 6.3 SURFACE WINDS: N. HEM 996 mb 1112mb 992 mb 1116mb L H Apparent Coriolis force Pressure gradient force Gradient wind Apparent centrifugal force Friction force Figure 6.4 6 2/14/11 SUMMARY OF WINDS Geostrophic wind (2 forces; straight winds aloft)   pressure gradient force   apparent Coriolis force Gradient wind (3 forces; curved winds aloft)   pressure gradient force   apparent Coriolis force   apparent centrifugal force Surface winds between straight isobars (3 forces; straight)   pressure gradient force   apparent Coriolis force   friction force Surface wind around pressure centers (4 forces; curved)   pressure gradient force   apparent Coriolis force   apparent centrifugal force   friction force GLOBAL CIRCULATION - MACROSCALE   Macroscale systems are tied to the global energy budget 7 2/14/11 L HADLEY’S SINGLE-CELL MODEL H Cold Easterly Trade Wind Warm L West H Warm L Easterly Trade Wind Cold H L THREE-CELL MODEL L Polar cell H Polar high - 90 oN Ferrel cell H Subpolar low - 60 oN Polar easterlies Southwesterlies Subtropical high - 30 oN (Horse latitudes) L L Hadley cell H Northeast trade winds West L Equatorial low - 0 oN (Doldrums), ITCZ H East Southeast trade winds Subtropical high - 30 oS Northwesterlies Subpolar low 60 oS Polar easterlies Hadley cell L H L Ferrel cell Polar high - 90 oS Polar cell L H H Figure 6.5 8 2/14/11 MACROSCALE SYTEMS  General circulations  Semi-permanent highs  Jet Streams 9 ...
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