Geoscience Reference
In-Depth Information
(a)
(b)
Water vapor measurement
Figure 7.8
(a) Schematic
diagram of a Campbell
Scientific Bowen ratio/energy
budget system for measuring
latent and sensible heat with
humidity measured by
ducting air alternately to a
common sensor; (b)
Schematic diagram of the
system used to duct air to the
common humidity sensor.
(From Campbell Scientific,
1987.)
Cooled
mirror
Dew
PT.
Pump
Adjustable
flow meters
Sounoid valve
controls which
input goes to
cooled mirror.
switched every
2 minutes
Air intakes
at two heights
2 liter containers
extends time constant
of vapor measurement
Similarly, integrating the product of the instantaneous value of
w
with the
instantaneous fluctuation in the volumetric heat content of the air, (
r
a
c
p
q
v
′
′
) gives
the time average sensible heat flux,
H
, i.e.:
Hc w
=
rq
apv
′
′
(7.8)
Thus, to measure the latent and sensible heat fluxes it is necessary to take
simultaneous, co-located measurements of the wind speed perpendicular to the
