ch 2 – atmospheric energy & temperature

Ch 2 – Atmospheric Energy Ch 2 – Atmospheric Energy & Temperature& Temperature

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature

• IntroductionIntroduction– In this chapter, we continue to build a In this chapter, we continue to build a

basic reference model of the atmosphere. basic reference model of the atmosphere. – Now we turn our attention to the energy Now we turn our attention to the energy

that drives the atmosphere.that drives the atmosphere.– Of particular interest is the source of Of particular interest is the source of

atmospheric energy (the sun).atmospheric energy (the sun).– We are interested in the details of energy We are interested in the details of energy

exchange and resulting atmospheric exchange and resulting atmospheric temperatures (Lester, 2006).temperatures (Lester, 2006).


• IntroductionIntroduction– These pieces of information are important These pieces of information are important

parts of the foundation of your parts of the foundation of your understanding of winds and weather.understanding of winds and weather.

– When you complete this chapter, you will When you complete this chapter, you will understand important sun-earth understand important sun-earth relationships and their seasonal and daily relationships and their seasonal and daily variations, modes of energy transfer variations, modes of energy transfer between the sun and earth, and between between the sun and earth, and between the earth and the atmosphere. (Lester, the earth and the atmosphere. (Lester, 2006).2006).


• IntroductionIntroduction– You will also learn some practical You will also learn some practical

aspects of measuring temperature and aspects of measuring temperature and details of global temperature patterns details of global temperature patterns (Lester, 2006).(Lester, 2006).


• Section A – Energy TransferSection A – Energy Transfer– Solar RadiationSolar Radiation

•Sun-Earth GeometrySun-Earth Geometry

•Radiation ProcessesRadiation Processes

•Terrestrial RadiationTerrestrial Radiation

– ConductionConduction– Convection/AdvectionConvection/Advection


• Section B – TemperatureSection B – Temperature– Temperature ScalesTemperature Scales– Temperature MeasurementsTemperature Measurements– Global Temperature DistributionGlobal Temperature Distribution

•Surface TemperaturesSurface Temperatures

•Upper Air TemperaturesUpper Air Temperatures


• Section A: Energy TransferSection A: Energy Transfer– Radiation – Radiation – the transfer of energy by the transfer of energy by

electromagnetic waveselectromagnetic waves– Conduction – Conduction – the transfer of energy through the transfer of energy through

molecular motionmolecular motion– Convection / Advection – Convection / Advection – refers to the refers to the

transfer of energy through the movement of transfer of energy through the movement of massmass

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature• Solar RadiationSolar Radiation

– Sun-Earth GeometrySun-Earth Geometry•Equinoxes – Equinoxes – at noon on the first days of spring and at noon on the first days of spring and

fall (the equinoxes), the sun’s rays are fall (the equinoxes), the sun’s rays are perpendicular to the earth’s surface at the equatorperpendicular to the earth’s surface at the equator

•Solstices – Solstices – On the first day of summer and the first On the first day of summer and the first day of winter (the solstices), the noonday sun day of winter (the solstices), the noonday sun reaches its highest and lowest latitudes, reaches its highest and lowest latitudes, respectivelyrespectively

•Solar elevation angle – Solar elevation angle – the influence of the the influence of the changing position of the sun relative to the earth is changing position of the sun relative to the earth is illustrated in terms of the solar elevation angle illustrated in terms of the solar elevation angle (angle of the sun above the horizon); figure 2-2(angle of the sun above the horizon); figure 2-2

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature• Radiation ProcessRadiation Process

– Absolute zero – Absolute zero – temperature where all molecular temperature where all molecular motion ceasesmotion ceases

– Solar declination – Solar declination – the latitude where the noon sun the latitude where the noon sun is directly Overheadis directly Overhead

– Speed of light – Speed of light – light is one of many types of light is one of many types of electromagnetic radiationelectromagnetic radiation

– Infrared (IR) – Infrared (IR) – frequencies lower than redfrequencies lower than red– Ultraviolet (UV) – Ultraviolet (UV) – frequencies higher than bluefrequencies higher than blue– Wavelength – Wavelength – (L) is the distance between two (L) is the distance between two

successive, identical wave features, such as two wave successive, identical wave features, such as two wave crestscrests

– Amplitude – Amplitude – (A) is half the distance between the (A) is half the distance between the lowest and highest points of the wavelowest and highest points of the wave


– Frequency – Frequency – (f) is the number of waves that pass (f) is the number of waves that pass some fixed point in a given time intervalsome fixed point in a given time interval•units of frequency are cycles per second (cps) or units of frequency are cycles per second (cps) or

Hertz (Hz)Hertz (Hz)– Spectrum – Spectrum – a useful diagram to illustrate the energy a useful diagram to illustrate the energy

of electromagnetic radiationof electromagnetic radiation•a graph of electromagnetic wave energy (A2) for all a graph of electromagnetic wave energy (A2) for all

electromagnetic waves verses their wavelengths; electromagnetic waves verses their wavelengths; Figure 2-4Figure 2-4

– Albedo – Albedo – there is a loss of approximately 30 percent there is a loss of approximately 30 percent of the incoming solar radiation due to reflection and of the incoming solar radiation due to reflection and scattering by clouds and other particulates and scattering by clouds and other particulates and reflection from the earth’s surfacereflection from the earth’s surface•this loss is called the albedo of the earth and its this loss is called the albedo of the earth and its

atmosphere; Figure 2-5atmosphere; Figure 2-5

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature• Terrestrial RadiationTerrestrial Radiation

– Heat capacity – Heat capacity – an important control of an important control of surface temperature is the heat capacity of the surface temperature is the heat capacity of the surface (ground or water)surface (ground or water)• in general heat capacity is the amount of in general heat capacity is the amount of

heat energy that is necessary to raise the heat energy that is necessary to raise the temperature of a substance by a certain temperature of a substance by a certain amountamount

• Greenhouse effect – Greenhouse effect – the capture of terrestrial the capture of terrestrial radiation by certain atmospheric gases is called radiation by certain atmospheric gases is called the greenhouse effect and the gases are called the greenhouse effect and the gases are called greenhouse gasesgreenhouse gases

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature• Conduction – Conduction – spoon left in a bowl of hot soupspoon left in a bowl of hot soup

– the energetic molecules in the hot end of the the energetic molecules in the hot end of the spoon transfer their momentum to the spoon transfer their momentum to the molecules in the cool end of the spoonmolecules in the cool end of the spoon

– hotter temperatures are conducted up the hotter temperatures are conducted up the handlehandle

• Convection / Advection – Convection / Advection – advection includes the advection includes the north-south movements of large warm and cold air north-south movements of large warm and cold air massesmasses– convection includes the large scale ascent and convection includes the large scale ascent and

descent of air masses and the smaller scale descent of air masses and the smaller scale development of thunderstormsdevelopment of thunderstorms


• Section B: TemperatureSection B: Temperature– Temperature Scales – Temperature Scales – temperature scales temperature scales

common to aviation are Fahrenheit and Celsius; common to aviation are Fahrenheit and Celsius; Figure 2-6Figure 2-6

– Temperature Measurements – Temperature Measurements – temperature temperature of the air measured at 1.5 meters (about 5 feet) of the air measured at 1.5 meters (about 5 feet) above the groundabove the ground

– measured in a standard instrument shelter in measured in a standard instrument shelter in the shade to protect the thermometer from the shade to protect the thermometer from direct solar radiation but allow the free direct solar radiation but allow the free ventilation of outside air; figure 2-7ventilation of outside air; figure 2-7


– Upper air temperatures – Upper air temperatures – other common other common temperatures used in aviation meteorology are temperatures used in aviation meteorology are those measured in the free atmospherethose measured in the free atmosphere•that is, above the earth’s surface; such that is, above the earth’s surface; such

temperatures are usually identified as temperatures are usually identified as temperatures aloft, as upper air temperatures, temperatures aloft, as upper air temperatures, or with reference to the height or pressure level or with reference to the height or pressure level where they are measuredwhere they are measured

– Indicated air temperature (IAT) – Indicated air temperature (IAT) – another another aviation-related temperature measurement is IAT aviation-related temperature measurement is IAT which is the temperature of the air as measured by which is the temperature of the air as measured by a temperature probe on the outside of an aircrafta temperature probe on the outside of an aircraft


– Outside air temperature (OAT) – Outside air temperature (OAT) – also called also called the true air temperature (TAT)the true air temperature (TAT)

•determined by correcting the measured or determined by correcting the measured or indicated air temperature for compression indicated air temperature for compression and friction heatingand friction heating

Ch 2 – Atmospheric Energy & Ch 2 – Atmospheric Energy & TemperatureTemperature• Sounding – Sounding – upper air temperatures are usually upper air temperatures are usually

measured directly with freely rising instrumented measured directly with freely rising instrumented balloons or soundings or by aircraftballoons or soundings or by aircraft– temperature soundings are also made from temperature soundings are also made from

weather satellites by relating temperature at weather satellites by relating temperature at various altitudes to measurements of radiant various altitudes to measurements of radiant energy emitted from the earth, clouds and energy emitted from the earth, clouds and various atmospheric gasesvarious atmospheric gases


• Global Temperature DistributionGlobal Temperature Distribution– Surface TemperaturesSurface Temperatures

•Temperature gradient – Temperature gradient – a temperature a temperature gradient is defined as the change of gradient is defined as the change of temperature divided by the distance over temperature divided by the distance over which the change occurswhich the change occurs

– where the isotherms are close together, where the isotherms are close together, gradients are relatively strong (large gradients are relatively strong (large temperature change over a small temperature change over a small distance)distance)


• Upper Air Temperatures – Upper Air Temperatures – Figure 2-9; Figure 2-9; temperatures in degrees Celsius at 500 mb temperatures in degrees Celsius at 500 mb (about 18,000 feet, 5,500 meters MSL) for the (about 18,000 feet, 5,500 meters MSL) for the Northern HemisphereNorthern Hemisphere– temperatures in degrees Celsius at 100 mb temperatures in degrees Celsius at 100 mb

(about 53,000 feet, 16,000 meters MSL) for the (about 53,000 feet, 16,000 meters MSL) for the Northern HemisphereNorthern Hemisphere

•relatively cold and warm regions labeledrelatively cold and warm regions labeled

SummarySummary

• The source of energy for the atmosphere The source of energy for the atmosphere is solar radiation.is solar radiation.

• The variety of temperature patterns over The variety of temperature patterns over the globe is partly the result of the tilt of the globe is partly the result of the tilt of the earth’s axis, the rotation of the earth, the earth’s axis, the rotation of the earth, and its orbit about the sun.and its orbit about the sun.

• Additionally, many physical processes Additionally, many physical processes redistribute heat energy in the redistribute heat energy in the atmosphereatmosphere

• These include terrestrial radiation in the These include terrestrial radiation in the presence of certain radiation-absorbing presence of certain radiation-absorbing gases, conduction, and gases, conduction, and convection/advection (Lester, 2006).convection/advection (Lester, 2006).

SummarySummary

• In subsequent chapters we will see In subsequent chapters we will see that these redistribution processes that these redistribution processes and resulting temperature patterns and resulting temperature patterns are the root causes of atmospheric are the root causes of atmospheric winds and weather (Lester, 2006).winds and weather (Lester, 2006).

ch 2 – atmospheric energy & temperature

Documents

transfer of energy

source of atmospheric

energy transferradiation

modes of energy transfer

details of energy exchange

earth relationships

solar elevation angle

wave crestsamplitude