Atmospheric Heat and HumidityAtmospheric heating Mechanisms of heat transferThe electromagnetic spectrumAverage distribution of incoming solar radiationThe heating of the atmosphereTemperature measurement Weather instrument shelterNorth America isothermsControls of TemperatureLand-water relationshipTemperature comparison Seattle, SpokaneTemperature comparison Vancouver, WinnepegTemperature comparison Eureka, NYCChanges in temperature with change in elevationEarth’s atmosphere is heated from belowTemperature comparison Quito, GuayaquilGeneral circulation of the atmosphereGeographic positionCloudinessCloudy dayCloudy nightJanuary temperatureJuly temperatureJan and July tempsLatent Heat of WaterLatent heat of waterFrost on windowHumidityRelative humidity—lowering temperatureHumidity-temperature daily trendDew on spiderwebChanges of humidityRelative humidity—constant temperatureSling psychrometerChanges in temperature with change in elevationGases cool as they expandAdiabatic lapse rateAdiabatic lapse rateCooling by lifting—adiabaticsOrographic liftingRain shadowWarm front liftingConvergent liftingConvective liftingHot air balloonsStable conditionsConditional stability1Atmospheric Heat and HumidityAtmospheric 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 16.17Average distribution of incoming solar radiationFigure 16.19The heating of the atmosphereFigure 16.212Temperature measurement Daily maximum and minimumOther measurements calculated from these• Daily mean temperature • Daily range• Monthly mean• Annual mean• Annual temperature rangeWeather instrument shelterNorth America isotherms Controls of Temperature•Day length• Sun angle• Land-water relationship• Geographic position relative to general circulation of the atmosphere and ocean• Altitude• CloudinessLand-water relationship• Water moderates the temperature• Warmer winters and cooler summers near large bodies of waterTemperature comparisonSeattle, Spokane3Temperature comparisonVancouver, WinnepegTemperature comparisonEureka, NYCChanges 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 ftTemperature comparisonQuito, GuayaquilGeneral circulation of the atmosphere4Geographic 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 continentsCloudiness• Daytime clouds shade surface, reflect energy away from area• Nighttime clouds blanket area, reflect heat energy back toward Earth’s surfaceCloudy day Cloudy nightJanuary temperatureJuly temperature5Jan and July temps Latent Heat of Water• Heat energy that water releases or absorbs when it changes phase• Gains it from environment as it melts or evaporates– So it cools the environment• Loses it when it freezes or condenses– So it warms the environmentLatent heat of waterFrost on windowHumidity• Description of how much water air contains• Relative Humidity compares how much moisture is in the air, to how much moisture the air could hold• The amount of water that air can hold is a function of temperatureRelative humidity—lowering temperature6Humidity-temperature daily trendDew on spiderwebChanges of humidity• Can warm or cool air, and not change water content• Will result in different relative humidity• Can increase or decrease water content of air without change in temperatureRelative humidity—constant temperatureSling psychrometerChanges in temperature with change in elevation• Two different mechanisms– Earth’s atmosphere is heated from below– Gases cool as they expand7Gases cool as they expand• Still have same heat energy• Take up larger volume• Increase in volume at lower pressure• Atmospheric pressure declines with altitude• Temperature change due to change in volume called “Adiabatic lapse rate”Adiabatic lapse rate• Temperature declines with lowering pressure, as air moves to higher altitude• Temperature increases with increasing pressure, as air moves to lower altitude• Rate of temperature change depends on saturation• Saturated air has condensation of water, which releases heat: warms environment¾10oC / 1000 m if not saturated¾6oC / 1000 m if condensation is occurringAdiabatic lapse rate Cooling by lifting—adiabaticsOrographic liftingRain shadow8Warm front liftingConvergent liftingConvective lifting Hot air balloonsStable conditions Conditional
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