Geoscience Reference
In-Depth Information
Table 12.2
Recommended minimum rain gauge densities for different types of
topographic and climate regions as recommended by the World Meteorological
Organization.
Area per gauge (km
2
)
Normal
tolerance
Extreme tolerance in
adverse conditions
Nature of the area
Small mountainous islands with
irregular precipitation
25
-
Mountainous regions in temperate,
Mediterranean, and tropical
areas
100-250
250-2000
Flat regions in temperate,
Mediterranean, and tropical areas
600-900
900-3000
Arid and polar areas
1500-10 000
-
Table 12.3
Minimum number of randomly
located gauges needed for adequate estimation of
monthly rainfall (Data from Stephenson, 1968).
Area (km
2
)
Number of gauges needed
100
5
200
6
500
8
1000
10
2000
13
5000
17
10 000
20
25 000
25
50 000
29
100 000
33
500 000
36
Snowfall measurement
Three major problems associated with measuring snowfall with gauges are as
follows:
(1)
Snow is easily blown by wind, much more so than is rain. Consequently, the
under-measurement due to near-gauge turbulence is exacerbated and this
problem is further compounded by snow that has been deposited in the
