Standards for weather stations

The Station at the Monterey, CA WSO

I’ve received a few requests for information regarding just what the established standards are for placing weather stations as they relate to their surroundings. Here is an excerpt from the NWS web page describing the issue, along with an embedded link to the PDF document that gives specific details:

The [National Weather Service] COOP network has provided climate and weather data for over 100 years.

Consistency of the measurements is an attribute of the network, and it has been

maintained by rare and/or gradual change, and established standards for

exposure, of instruments over the life of the network. In order to preserve the

integrity of the network, NWS has

established

standards for equipment, siting, and exposure.

By these standards, the Stevenson Screen at the NWS office in Monterey, CA shown above, is well out of compliance.

Temperature sensor siting: The sensor should be mounted 5 feet +/- 1 foot

above the ground. The ground over which the shelter [radiation]

is located should be typical of the surrounding area. A level, open clearing is

desirable so the thermometers are freely ventilated by air flow. Do not install

the sensor on a steep slope or in a sheltered hollow unless it is typical of the

area or unless data from that type of site are desired. When possible, the

shelter should be no closer than four times the height of any obstruction (tree,

fence, building, etc.). The sensor should be at least 100 feet from any paved or

concrete surface.

Precipitation gauge siting: The exposure of a rain gauge is very

important for obtaining accurate measurements. Gauges should not be located

close to isolated obstructions such as trees and 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. 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. As a general rule, the windier the gauge location is, the greater the

precipitation error will be.

Advertisements