Geoscience Reference
In-Depth Information
Figure 4.22 mean annual out-
going longwave radiation on
Earth in watts per cubic me-
ter. The original source of this
radiation was the Sun. The ra-
diation was then absorbed and
stored by the Earth until its re-
lease as longwave energy. Note
the geography of this process,
with most longwave radiation
being released in the tropical
latitudes.
have a net surplus of radiation, whereas others have a net defi-
cit. In addition, a particular place may have a net surplus of
radiation during one time of year but a net deficit at another.
These net differences are important because they are the driv-
ing mechanism behind climate and many physical processes,
such as atmospheric circulation and evaporation. Four pri-
mary factors influence net radiation around the globe: (1) the
Sun's angle of incidence, (2) latitude, (3) seasonality, and (4)
length of day. Secondary factors include the varying output of
the Sun due to sunspots and solar flares, the elliptical nature
of the Earth's orbit, changes in the thickness and properties
of the atmosphere, and variability in the length of day. The
best way to understand the changes in net radiation across the
globe is by focusing on the four primary factors because they
work in a holistic way.
Remember that the angle at which solar radiation strikes
Earth directly affects absorption and reflection. This angle is
primarily a function of latitude, with low latitudes having high
Sun angles and high latitudes having low Sun angles. There-
fore, low latitudes receive high amounts of radiation and have a
net annual surplus, whereas the high latitudes have a net deficit
because they receive less direct radiation (Figure 4.23).
www.wiley.com/college/arbogast
The global Energy budget
After you have examined Figure 4.21, view The Global Energy
Budget . This animation allows you to better visualize the flow of
solar radiation from the Sun to Earth. As you watch it, notice the
various pathways that radiation takes as it interacts with the atmo-
sphere. In addition, try to integrate all the concepts introduced so
far in this chapter to solidify your understanding of the global en-
ergy budget. Once you complete the animation, be sure to answer
the questions at the end to test your understanding of this concept.
Figure 4.23 mean annual net
radiation at the top of the at-
mosphere on Earth. Note the
relationship between color and
value (watts per square meter),
which is indicated in the key to
the right of the image. Low to
middle latitudes have a net sur-
plus of radiation, whereas high
latitudes have a net deficit.
 
 
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