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Rain measurement: Difference between revisions
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The exposure of a rain gauge is very important for obtaining accurate measurements. As a general rule, the windier the gauge location is, the greater the precipitation error will be. You can find lots of discussions online about wind effects, and rain shadows, together with research on positioning requirements in rural and urban locations. A good starting point is [http://www.rmets.org/weather-and-climate/observing/guidelines-observing-0 this UK website].
Gauges should not be located close to isolated obstructions such as trees or buildings, which may deflect precipitation due to erratic turbulence. To avoid wind and resulting turbulence problems, do not locate gauges in wide-open spaces or on elevated sites, such as the tops of buildings. For a separate rain gauge (e.g. Fine Offset), experiment to find whether the best protection from the wind occurs with the buckets arranged to line up with the mast or at right angles to the supporting arm between gauge and mast.
The WMO recommend that a rain gauge be placed away from any nearby obstacle a distance of at least twice the height of the obstacle. The best site for a gauge is one in which it is protected in all directions, such as in an opening in a grove of trees. The height of the protection should not exceed twice its distance from the gauge.
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