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Figure 3.1. Zonal averages
(averages by latitude) of the
annual mean net radiation budget
at the top of the atmosphere
based on ERBE data (from
Trenberth and Caron, 2001 , by
permission of AMS).
Figure 3.2. The global pattern of the annual mean net radiation budget at the top of
the atmosphere based on ERBE data (from Trenberth et al., 2001 , by permission of
Springer-Verlag).
the planetary albedo. If radiation balance held at all latitudes, the latitudinal distri-
bution of TOA outgoing longwave radiation would match that of the net TOA solar
radiation. But this is not what is observed. Satellite data, such as from the Earth
Radiation Budget Experiment (ERBE) (February 1985 through April 1989) and the
follow-on CERES effort (Clouds and the Earth's Radiant Energy System) show that
for annual averages, between about 38°N and 38°S, the earth receives more radi-
ation than it emits to space (R top is positive). Poleward of these latitudes, the earth
emits more radiation than it receives (R top is negative) ( Figures 3.1 and 3.2 ).
3.1.2
Poleward Energy Transports
The implication of Figures 3.1 and 3.2 is that there must be poleward transports
of energy by the atmosphere and oceans that warm the polar regions and cool the
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