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
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
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.