Geoscience Reference
In-Depth Information
4.4. Consider a unit area (1 m
2
) flat plate sitting in space at a distance from the
sun equal to the average earth-sun distance and oriented perpendicular
to the solar beam. The back of the plate is insulated, so emission from the
plate can come only from the side facing the sun. Assuming that the plate
behaves as an idealized blackbody with emissivity of 1, what will be the
temperature of the plate? What will be the temperature of the plate if the
back is not insulated? What will be the temperature if the insulated plate is
oriented at a 45° angle to the solar beam?
4.5. The atmosphere of Mars is much thinner than that of Earth, with surface
pressure of only 8 hPa on average, but it is about 95% CO
2
, a greenhouse
gas. About 10% of the longwave radiation from the surface is absorbed
by the Martian atmosphere. Use the slab-atmosphere greenhouse model
to estimate the radiative equilibrium temperature of Mars and its surface
temperature. Assume that the planetary albedo is 0.15.
4.6. Consider solar radiation of wavelength l, assumed to be in parallel beams,
incident at the top of a slab atmosphere with intensity
I
0
. This idealized
atmosphere contains a uniform distribution of molecules that absorb all the
radiation at wavelength l incident on them. These molecules have a radius
of 5 mm and their number density is 3 10
6
m
−3
.
By what percentage will the original intensity of the beam be reduced
due to absorption after it travels 2 km through this atmosphere? At what
distance from the top of the atmosphere is the optical depth equal to 1?
(Neglect scattering and thermal emission.)
4.7. (a) During a warm ENSO event, sea surface temperatures increase by
about 3 K in the central equatorial Pacific Ocean. For the clear-sky
case, what change (sign and magnitude) in OLR over the central Pacific
accompanies this warming?
(b) Also during a warm ENSO event, deep convection moves from the
western Pacific to the central Pacific. Assuming that there are no clouds
over the central Pacific when a warm event is not in progress, what
change in OLR over the central Pacific accompanies this change in the
distribution of deep convection? (Assume that the convective clouds
cover the full depth of the troposphere.)
(c) What magnitude and sign of OLR anomaly would you expect to
observe over the central equatorial Pacific during an ENSO event?
