Site Selection Criteria

In order to make accurate measurements of climate across multiple decades, many criteria are considered before selecting a site and establishing a USCRN station. The primary criteria include:

Sensitivity to the measurement of climate variability and trends : Locations should be representative of the climate of the region, and not heavily influenced by unique local factors. This primary criterion is called spatial representativeness.
Long term site stability : Consideration is given to whether the area surrounding the site is likely to experience major change within 50 to 100 years. The risk of human encroachment over time and the chance the site will close due to the sale of the land or other factors are evaluated. Federal, state, and local government land often provide a high stability factor. Population growth patterns are also considered. This primary criteria is called temporal stability.
Other secondary criteria involve naturally occurring risks and variability, and logistical concerns :
- Flood plains and locations in the vicinity of orographically induced severe winds like the Santa Ana and the Chinook are avoided.
- Locations with persistent periods of extreme snow depths are avoided where possible, although in Alaska this may be unavoidable in maritime regions.
- Locations near existing or former observing sites with long records of daily precipitation and maximum and minimum temperature are desirable.
- Nearby availability of personnel with an understanding of climate observing systems is desirable.
- Relatively easy year round access by vehicle for installation and periodic maintenance is favored.

A density study was conducted to determine the number of general geographic locations that would provide the best possible coverage in the different U.S. climate regions, given budget constraints. Digital topographic maps and a climatological profile of the locations proposed for stations are examined, and aerial photographs are studied. The need for unchanging physical surroundings, particularly avoiding encroachment by man-made structures, means there is some flexibility in adjusting the optimal geographic location to take advantage of a more stable location near a targeted site.