1Earth-Sun RelationsThe AtmosphereEarth-Sun relations Earth motions • Rotates on its axis• Revolves around the SunSeasons—Result of constant axial tilt• Changing Sun angle • Changing length of daylight Plane of the EclipticEarth-Sun RelationsPlane of the Ecliptic Sun incidenceSun Angle--Equator Sun Angle—Mid-Latitude Sun Angle—High Latitude2Sun Angle with Latitude Sun incidence Equinox and SolsticeSolar latitudesEarth-Sun relations Special days • Solstice—Sun's vertical rays are located at the Tropic (23½º latitude) • June 21-22 • December 21-22• Equinox—Sun’s vertical rays located at the Equator (0olatitude)• March 21-22• September 21-22Highest SunLowest Sun Midnight Sun Daylight at Solar latitudes3Atmospheric heating Heat is always transferred from warmer to cooler objects Mechanisms of heat transfer • Conduction• Convection • Radiation (electromagnetic radiation) Mechanisms of heat transferFigure 16.16The electromagnetic spectrumFigure 16.17The heating of the atmosphereFigure 16.21Average distribution of incoming solar radiationFigure 16.19Proportional volume of gases that compose dry airFigure 16.3Composition of the atmosphereAir is a mixture of gasesMajor components of clean, dry air • Nitrogen (N) – 78%• Oxygen (O2) – 21%• Argon and other gases • Carbon dioxide (CO2) – 0.036% – absorbs heat energy from Earth Variable components of air• Water vapor • Aerosols• OzoneDust and aerosols4Figure 16.5Atmospheric pressure variation with altitudeThermal structure of the atmosphereFigure 16.7Atmospheric layers based on temperature•Troposphere•Stratosphere• Mesosphere• ThermosphereWeather BalloonWeather instrument shelterTemperature measurement Daily maximum and minimum are measuredOther values calculated from these• Daily temperature range• Daily mean temperature • Monthly mean temperature• Annual mean temperature• Annual temperature rangeNorth America isotherms Isotherm• Line of equal temperature• Divides map into areas warmer than that temperature and areas cooler than that temperature• Maps with isotherms use constant difference from one isotherm to the next• Often colored for ease of understandingMonthly Temperatures vs. Latitude5Temperature comparisonVancouver, WinnepegLand-water relationship• Water moderates the temperature• Warmer winters and cooler summers near large bodies of waterTemperature comparisonQuito, GuayaquilChanges in temperature with change in elevation• Two different mechanisms– Earth’s atmosphere is heated from below– Gases cool as they expandEarth’s atmosphere is heated from below• It is warmer closer to the sea level• It is cooler at higher altitudes• Environmental lapse rate– About 6.5oC / 1000 m– About 3.5oF / 1000 ftCloudy dayCloudy night Cloudiness• Daytime clouds shade surface, reflect energy away from area• Nighttime clouds blanket area, reflect heat energy back toward Earth’s surfaceTemperature comparisonEureka, NYC6Temperature comparisonSeattle, SpokaneGeographic position• Western sides of ocean basins get equatorial heat from ocean currents– More moderate winter temperatures on east coasts of continents• Eastern sides of ocean basins have cold polar currents– Cooler year-round temperatures on west coasts of continentsNorth America isothermsControls of Temperature• Day length• Sun angle• Land-water relationship• Geographic position relative to general circulation of the atmosphere and ocean• Altitude• CloudinessGeneral circulation of the atmosphereJanuary temperatureJuly temperatureJan and July
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