9/16/20101Geography 1001:Climate & VegetationLecture 7: Global Temperature and Atmospheric PressureSeptember 16, 2010Dr. Holly BarnardTest Results0 5 10 15 2028.035.340.245.049.753.958.162.366.971.876.781.285.489.693.898.6FrequencyScoreGEOG 1001 Midterm 1 Grade DistributionEarth’s Temperature Patterns• Isotherm is an isoline – a line along which there is a constant value.• In this case it portrays a line that connects points of equal temperature creating a contour map pattern of temperature.• Thermal equator is an isotherm connecting points of highest mean temperatureIsotherm9/16/20102• January Temperature Map– Thermal equator movement southward– More pronounced over large continents• July Temperature Map– Thermal equator movement northward– More pronounced over large continents• Annual Temperature Range Map– Continentality Earth’s Temperature PatternsJanuary TemperaturesFigure 5.14(b)(c)(a)January TemperaturesFigure 5.14July TemperaturesFigure 5.179/16/20103July TemperaturesFigure 5.16Global Temperature RangesFigure 5.19Pressure and winds Outline• Intro• Wind Essentials• Driving Forces Within the Atmosphere9/16/20104Introduction: Earth’s atmospheric circulation transfer both energy and mass at grand scale• Imbalance between equatorial energy surplus and polar energy deficit• Create– Weather & ocean currentsLatitudinal temperature gradientpressure instability Surplus of energyDeficitDeficitAtmospheric Circulation• Primary (1º) Circulation: general worldwide circulation• Secondary (2º) Circulation: high and low pressure systems• Tertiary (3º) Circulation: local winds and temporal weather patterns Wind Essentials• Air Pressure– Gravity (elevation)– Motion, size & number of air moleculesdetermine temperature & density of airdetermine Air pressure• Measurement of Pressure– Mercury barometer– Aneroid barometer9/16/20105Gravity’s role on air↑Altitude ↓ gravity ↓densityAtmospheric Pressure• Normal Sea Level Pressure– 1013.2 mb (millibar) force per square meter of surface area– 29.92 in. mercury (Hg)– Also expressed in Kilopascals (101.32 kPa)– 1 kPa = 10mb• Barometer– Measures air pressure– From Greek word baros or weightBarometers: Figure 6.2Wind Essentials II• Wind: – Description • Name and direction• Westerly• Easterly– Measurement• All, but only horizontal• Anemometer • Wind vane9/16/20106Global wind direction: in a Non-rotating earthGlobal wind direction Driving Forces Withinthe Atmosphere• Pressure Gradient (Force; PGF)• Coriolis Acceleration• Friction Horizontal windsPressure GradientFigure 6.79/16/20107Pressure Gradient Force Key detail!• PGF• Coriolis• Friction•Can get the wind going from Zero•Only on objects already movingCoriolis ForceThe apparent deflection of moving objects (wind, ocean currents, airplanes) from travelling in a straight path- in proportion to the speed of the Earth’s rotation at different latitudes (speed = distance/time)Coriolis Force9/16/20108Pressure + CoriolisGeostrophic windsPressure + Coriolis + FrictionFigure 6.8Wind Pattern Development9/16/20109Summary• Global Temperature Distribution• Air Pressure Measurement• Pressure Force• Coriolis Force• Friction
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