Weather and climate Weather and climateComposition of the atmosphereProportional volume of gases that compose dry airComposition of the atmosphereDust and aerosolsStructure of the atmosphere Thermal structure of the atmosphereWeather BalloonEarth-Sun relations Earth-Sun relations Relationship of sun angle to the path of solar radiation Animation of Earth’s orbitEarth-Sun relationshipsCharacteristics of the solstices and equinoxesAtmospheric heating Mechanisms of heat transferThe electromagnetic spectrumAtmospheric heating Average distribution of incoming solar radiationAtmospheric heating The heating of the atmosphereTemperature measurement Mean monthly temperatures for two locations in CanadaMean monthly temperatures for Eureka, California and New York CityControls of temperature World mean sea-level temperatures in JanuaryWorld mean sea-level temperatures in JulyWeather and climate Weather • Weather is over a short period of time • Constantly changingClimate• Climate is over a long period of time • Generalized, composite of weatherWeather and climateElements of weather and climate • Temperature• Humidity• Cloudiness• Precipitation• Air Pressure• Winds speed and directionComposition 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 EarthProportional volume of gases that compose dry airFigure 16.3Composition of the atmosphereVariable components of air • Water vapor • Aerosols•OzoneDust and aerosolsFigure 16.5Atmospheric pressure variation with altitudeStructure of the atmosphere Atmospheric layers based on temperature • Troposphere• Stratosphere• Mesosphere• ThermosphereThermal structure of the atmosphereFigure 16.7Weather BalloonEarth-Sun relations Earth motions •Rotates on its axis• Revolves around the SunSeasons• Result of constant axial tilt• Changing Sun angle • Changing length of daylightEarth-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 21-22Relationship of sun angle to the path of solar radiation Figure 16.11Animation of Earth’s orbitEarth-Sun RelationsEarth-Sun relationshipsFigure 16.12Characteristics of the solstices and equinoxesFigure 16.13Atmospheric 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 16.17Atmospheric heating Incoming solar radiation • Atmosphere is largely transparent to incoming solar radiation • About 50% absorbed at Earth's surface • Atmospheric effects• Reflection – albedo (percent reflected)• Scattering• Absorption• Most visible radiation reaches the surfaceAverage distribution of incoming solar radiationFigure 16.19Atmospheric heating Earth re-radiates energy at the longer wavelengths (infra-red: heat)• Longer wavelength terrestrial radiation is absorbed by • Carbon dioxide and • Water vapor in the atmosphere • Lower atmosphere is heated from Earth's surface • Heating of the atmosphere is termed the greenhouse effectThe heating of the atmosphereFigure 16.21Temperature measurement Daily maximum and minimumOther measurements calculated from these• Daily mean temperature • Daily range• Monthly mean• Annual mean• Annual temperature rangeMean monthly temperatures for two locations in CanadaFigure 16.24Mean monthly temperatures for Eureka, California and New York CityFigure 16.26Controls of temperature Receipt of solar radiation is the most important controlOther important controls• Differential heating of land and water • Altitude• Geographic position• Cloud cover• AlbedoFigure 16.28Clouds reducethe daily temperature rangeWorld mean sea-level temperatures in JanuaryFigure 16.29World mean sea-level temperatures in JulyFigure
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