Environmental Engineering Reference
In-Depth Information
There are many different types of cumulus cloud, subdivided on the basis of their
appearance. If an inversion
Plate 4.3
Fair-weather cumulus clouds over north Wales. The
level cloud base and cloud tops can easily be seen.
Photo: Peter Smithson.
of temperature exists, as often happens with anticyclones, the bubbles will rise to the
inversion and then start to level out or descend, evaporating the cloud droplets as they do
so. This type of cloud is known as fair-weather cumulus, as it never grows sufficiently to
give rain (Plate 4.3). Where there is no inversion to prevent upward growth the cloud
may build up as far as the tropopause and give heavy rain.
For rain to fall, we need clouds, but many clouds survive for hours without giving
rain. What special circumstances enable some clouds to produce rain whereas others give
none?
PRECIPITATION
FORMATION OF PRECIPITATION
On the summit of Mount Waiaeale, Kauai, Hawaii, average annual precipitation is 11,684
mm. In terms of the amount of water, this is equivalent to 100,000
t
ha
−1
y
−1
. Without
