Geoscience Reference
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but also growth by the very efficient (often dominant) Bergeron-Findeisen
process. Hence the potential for producing precipitation size particles is
much higher.
Which clouds produce rain?
: clouds are more likely to produce rain if they
have existed for some time, have significant depth, and have high water
content.
●
Precipitation form
: there is distinction between (a) liquid precipitation
falling as rain or drizzle (distinguished mainly by drop size); and (b) frozen
precipitation (distinguished by morphology and whether melting or other-
wise at ground level).
●
Raindrop size
: ground observations suggest the number of drops falls off
exponentially with drop size at a rate related to a rainfall rate, approximately
following the Marshall-Palmer equation, i.e.,
●
ND N
l
()
=
e
D
−
o
Rain rate and kinetic energy
: rain rate and the kinetic energy of rain can be
written as integrals of (empirical expressions for) terminal velocity and drop-
let size distribution: this forms the basis for soil erosion equations used in
hydrology.
●
Frozen precipitation
: numerous forms of frozen precipitation are recognized
but there is marked distinction between snow/sleet (from multi-layer,
stratiform clouds in cold weather) and ice pellets/hail (most intense from
convective cloud).
●
Other forms of precipitation
: deposition of water from the atmosphere as
dew or frost can be significant in moist, cool climates in winter, and the inter-
ception of mist or cloud by vegetation can be important locally, especially in
coastal regions.
●
References
Doviak, R. & Zrnic, D. (1984)
Doppler Radar Weather Observations
. Academic Press, New York.
Shiotsuki, Y. (1974) On the flat size distribution of drops from convective raincloud.
Journal
of the Meteorological Society of Japan,
52
(1), 42-59.
Smith, J.A. (1993) Precipitation. In:
Handbook of Hydrology
. (ed. D. Maidment), pp. 3.1-4.1.
McGraw-Hill, New York.
Sumner, G.N. (1988)
Precipitation Process and Analysis
. John Wiley and Sons, Bath, UK.
