Heat Energy Solar and gravitational energy are the fundamental sources of energy for the Earth's...
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Transcript of Heat Energy Solar and gravitational energy are the fundamental sources of energy for the Earth's...
Heat Energy
Solar and gravitational energy are the fundamental sources of energy for the Earth's climate system.
Air-sea exchanges of heat (& freshwater) change density and drive circulation.
- heat source into the ocean is solar radiation
- heat lost from the ocean by:- latent heat (evaporation) - conduction (sensible) - longwave radiation - reflected solar
- ocean circulation moves (transports) heat
Geography 104 - “Physical Geography of the World’s Oceans”
heat out of top of atmosphere = 100%
Earth’s cooling: reflected solar radiation, longwave, latent, and sensible heat
atmosphere’s heat budget by %heat into atmosphere = 60%; 37% from land & ocean
heat out of atmosphere = 60%
Earth’s heat budget (W m-2)
Qsw = Qlw + Qlat + Qsens168 W m-2 = 66 W m-2 + 78 W m-2 + 24 W m-2
in balance; no net heating or cooling
Earth’s heat budget (W m-2)
Longwave radiation:Earth’s surface atmosphere = 350 W m-2
Atmosphere Earth’s surface = 324 W m-2
26 W m-2 heats atmosphere
ocean’s heat budget by %
Qsw = Qlw + Qlat + Qsens100% = 41% + 53% + 6%
on average no net heating or cooling
electromagnetic spectrum
units 1 nm = 10-9 m
EMR exhibits wave-like and particle-like properties. Indivisible particles of light are defined as photons.
blackbody radiation – blackbody is a perfect emitter and absorber of radiation (i.e. appears black). Blackbodies emit at all λ’s. However, λ of maximum emission is inversely proportional to temperature.
higher T
lower λ peak
Wien’s law: λmax ~ 1 / T
Stefan-Boltzmann formula: total energy emitted ~ T4
288 K Earth
- the atmosphere absorbs little (~5%) radiation in visible wavelengths-water vapor, CO2, methane, ozone, CFC’s, (and other greenhouse gases) absorb some of the infrared radiation emitted by the earth-with no greenhouse effect, Earth’s surface would average a frigid -18°C (0°F) -water vapor, clouds, and CO2 (in that order) produce the most greenhouse warming, raising Earth’s mean surface temperature to 15°C (59°F)
changing solar incidence angle
sun overhead at Tropic of Capricorn on summer solstice in southern hemisphere
24-hour sunlight southof Antarctic circle
changing solar incidence angle
sun overhead at Tropic of Cancer on summer solstice in northern hemisphere
24-hour sunlight northof Arctic circle
changing solar incidence angle
more reflection at high latitudes
longer path through atmosphere at high latitudes
Earth’s radius = 6371 kmatmosphere’s thickness ~100 kmso figure not to scale
solar radiation directly heats water beneath the sea surface
UV IR
~50% of solar energy attenuated in top 1 m
Most solar energy quickly “attenuated” by seawater and converted to heat. Some wavelengths can penetrate to depths of 100m
seawater and things in it alter the spectral shape of the solar field (“bio-optics”)
seawater and things in it have fairly unique light absorbing and scattering properties
solar radiation can be back-scattered to space
heat loss terms
- latent heat flux (Qlat) energy required to change state (evaporate) of
watermost important in tropics & midlatitudes
- longwave radiation (Qlw)net thermal IR emission from ocean
- sensible heat flux (Qsen)transfer from high to low temp. to equalize
differencetypically small
latent heat
evaporation process needs energy to overcome molecular forces of attraction between water particles; this input of heat energy causes a drop in ocean temperature
2. /
latent heat
Figure 7-11 in text; another error
3. /
0. Energy to heat 1 gm ice by 1 °C = 2.05 J/g
poleward heat transport via ocean & atmosphere
heat gain & loss vs. latitude
temperature of oceans ~ constant distribution of heat changes
surface warming decreases density (thus stratifies)
surface cooling increases density (thus destratifies)