Geoscience Reference
In-Depth Information
●
Soil heat flow equation
: the rate of change of soil temperature at depth is
given by the divergence of the equation describing thermal conduction, and
for homogeneous soil this becomes the product of the thermal diffusivity
with the second partial derivative of the soil temperature with depth.
●
Thermal wave in soil temperature
: assuming a sinusoidal daily cycle in soil
surface temperature and homogeneous soil, the thermal wave in the soil is
sinusoidal and relative to the surface wave has an amplitude less by a factor
(
z
/
D
) and phase (in radians) delayed by (
z
/
D
), where
D
(=
√
(
Pa
s
/
π
) is the
damping depth
and
P
is the
period
of the wave in seconds.
Damping depth
:
D
is 0.08 m and 0.12 m for the daily soil surface temperature
cycle, and 1.6 m and 2.24 m for the yearly cycle for dry sandy soil and wet
clay, respectively.
●
Surface soil heat flux
: is advanced by one eighth of a cycle with respect to
sinusoidal variations in soil surface temperature, i.e., by 3 hours for the daily
cycle and 1.5 months for the yearly cycle.
●
References
Deacon, E.L. (1969) Physical processes near the surface of the Earth. In:
World Survey of
Climatology,
Vo l . 1
, General Climatology
(ed. H.E. Landsberg). pp. 39-104. Elsevier,
Amsterdam.
Monteith, J.L. & Unsworth, M.H. (1990)
Principles of Environmental Physics
. Edward
Arnold, London.
