Presentation on theme: "Atmospheric Circulation"— Presentation transcript:
1 Atmospheric Circulation Geography “Physical Geography of the World’s Oceans”Atmospheric Circulationair moves because of pressure differenceslarge scale air motion is influenced by Coriolis effecthorizontal air motion drives ocean circulationatmosphere and ocean circulation have similaritiesGo slow, explain everything, reiterate big picture
2 greatest solar heating is in equatorial region more reflection at high latitudesEarth’s radius = kmatmosphere’s thickness ~100 kmso figure not to scalelonger path through atmosphereat high latitudes
6 Coriolis Effect (summary) Motions in a rotating frame will appear deflected to the right in the northern hemisphereMotions in a rotating frame will appear deflected to the left in the southern hemisphereMotions are not deflected on the equator, greatest deflection at poles, varies with latitude
7 vertical structure of atmosphere air temperature cools with height in troposphere
8 fluid motion is driven by spatial pressure differences
9 atmospheric circulation in its simplest form solar heating maximum at equator decreases air densitylight moist air rises decreasing atmospheric mass, thus lowering pressurerising air cools adiabaticallycooling causes condensation, rain and increases densityair moves poleward cooling and increasing densityheavy, cool, dry, air increases atmospheric mass, thus increasing pressurepressure difference gives rise to Hadley circulation
10 Ferrel’s three-cell model of atmospheric circulation low pressure (warm/wet) at equatorhigh pressure (cold/dry) at poles
11 Ferrel’s three-cell model of atmospheric circulation addition of Coriolis Effect gives global winds
18 Geostrophic FlowFor large scale motion, pressure and Coriolis are roughly in balance. This is referred to as geostrophic balance and gives rise to geostrophic flow.Stated another way, geostrophic flow arises from a balance of pressure and Coriolis “forces”.Geostrophic flow is along lines of constant pressure and its magnitude is proportional to the pressure gradient.
19 global winds and pressure; why we live in the west JulyJanuary
20 atmospheric circulation over North America map shows both pressure contours and wind vectors clockwise or anti-cyclonic rotation around a high in the northern hemisphere
21 atmospheric circulation over North America map shows both pressure contours and wind vectors counter-clockwise or cyclonic rotation around a low in the northern hemisphere
22 Sea Breeze – another mechanism for (local) winds
24 Indian MonsoonsMonsoon winds are not in geostrophic balance because winds are not along lines of constant pressure. Thus, pressure and Coriolis are not in balance.Northeast or Winter MonsoonSouthwest or Summer Monsoon
27 Northeast - The system that brought the rain and snow across the Northeast yesterday will continue to do so today, but precipitation should generally be lighter than it was on Tuesday.West - Warm temperatures are expected again across the West with an upper level ridge continuing to be the dominant weather feature in the region. An upper level trough will begin to move into the West Coast tomorrow night and Friday, breaking down the ridge that's been in place.