Environmental Engineering Reference
In-Depth Information
2.4
Earth radiation balance. From ERBE (2005).
and 48 W/m
2
, and the values of net AW radiation, 111
W/m
2
and 114 W/m
2
(NASA 2005).
Moreover, two decades of accurate data from satellite
observations have shown that the decadal variability of
both SW and LW fluxes at the top of the atmosphere
is much larger than previously thought. Since the early
1990s tropical anomalies of emitted LW flux as large as
5-8 W/m
2
have been associated with a decrease in trop-
ical cloudiness (due to El Ni˜o events), and SW-reflected
flux showed a large increase (nearly 10 W/m
2
) between
1991 and 1993 (due to aerosols from the Mount Pina-
tubo eruption) and decreased subsequently (Wielicki,
Wong, Allan et al. 2002). Chen, Carlson, and Del Genio
(2002) ascribed these changes primarily to decreased
convection, cloudiness, and upward motion above Indo-
nesia, whereas at other longitudes along the intertropical
convergence zone these processes actually increased.
Graphic representation of the global radiation balance
(fig. 2.4) charts the multiplicity of flows, with the mean
values given as percentages of the mean incident solar ra-
diation at the top of the atmosphere. Latent heat flux is
determined by the net radiation at the surface and over
