Geoscience Reference
In-Depth Information
PROBLEMS
1.1
Assuming that the average volume of water storage in the soil equals 0.05 m (if spread over the
entire Earth surface; see Table 1.3), and that the average precipitation on the land surfaces of the
Earth is equal to 0.8 m y
−
1
(Table 1.1), give an estimate (expressed in days) for the mean residence
time of soil water. Consider conditions to be steady, so that precipitation is in balance with runoff
and evaporation, and assume that all the precipitation infiltrates into the soil. What would this
residence time be, if it is assumed that only one half of the precipitation infiltrates directly into the
soil, and that the remaining half immediately evaporates as interception or runs off on the surface?
1.2
Recent estimates of the average surface energy fluxes at the global scale (Table 1.4) are as follows;
the net radiation
R
n
=
104Wm
−
2
, the latent heat flux
L
e
E
=
85Wm
−
2
, and the turbulent sensible
heat flux
H
=
19Wm
−
2
. Express these fluxes as equivalent quantities of liquid water evaporated
in units of mm y
−
1
. Assume that the latent heat of vaporization of water is roughly
L
e
=
2
.
5
×
10
6
Jkg
−
1
and the density
ρ
w
=
10
3
kg m
−
3
.
