Standards for weather station siting using the new CRN


NOAA has put together a new series of surface stations called the


Reference Network (CRN) As a specialist in the technology of meteorology, I

like this program a lot. It takes great care to place emphasis on accuracy,

repeatability, linearity. and calibration of instruments. The best feature, as

far as I’m concerned is the use of three simultaneous aspirated and calibrated

air temperature probes, so that there is redundancy. And if one sensor starts

drifting it will show up against the data from the other two. Dr. Tom Karl from NCDC

deserves credit for bringing this project to implementation.

While this new instrumentation will ensure far more accurate in situ

measurements in the future, it will do little to help the disarray seen in the

surface temperature record of the past.

Here is the manual for it:


CRN Series December 10, 2002

X030 DCN 06

I want to bring attention to the way in which they rate weather station

locations, because it is very germane to the argument that some of the existing

USHCN and COOP stations have micro-site issues. As far as I know, no database

exists of the ratings below applied to the existing network of weather stations.

From the USHCRN manual:

The USCRN will use the classification scheme below to document the

"meteorological measurements representativity" at each site.

This scheme, described by Michel Leroy (1998), is being used by Meteo-France

to classify their network of approximately 550 stations. The classification

ranges from 1 to 5 for each measured parameter. The errors for the different

classes are estimated values.

  • Class 1 – Flat and horizontal ground surrounded by a clear

    surface with a slope below 1/3 (<19deg). Grass/low vegetation ground cover <10 centimeters high. Sensors

    located at least 100 meters from artificial heating or reflecting surfaces, such as

    buildings, concrete surfaces, and parking lots. Far from large bodies of water, except if it is

    representative of the area, and then located at least 100 meters away. No shading when the sun

    elevation >3 degrees.


  • Class 2 – Same as Class 1 with the following differences.

    Surrounding Vegetation <25 centimeters. Artificial heating sources within 30m. No shading for a sun elevation >5deg.


  • Class 3 (error 1C) – Same as Class 2, except no artificial heating sources within 10 meters.

  • Class 4 (error >= 2C) – Artificial heating sources <10 meters.


  • Class 5 (error >= 5C) – Temperature sensor located next to/above

    an artificial heating source, such a building, roof top, parking lot, or concrete surface."

One of the goals of the project, will be to apply this site classification

standard set forth by NOAA for the USCRN to the existing network of surface

stations so that the problems associated with some sites can be quantified, and

the good sites can be clearly defined as well. This will help scientists whom

use the surface temperature data do more accurate analyses.

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July 3, 2007 10:24 pm

Is the idea to assess each station as you go along, or to do them all at the end?

Anthony Watts
July 3, 2007 11:55 pm

I plan on waiting to start applying the rating criteria when we’ve reached the 10% point of the nationwide survey, and then add the rating to each site as the survey progresses.

July 4, 2007 7:41 am

With the number of problems that some of these have and if a Class 5 is referring to only a single artificial heating source at 5C correction, then I suspect you may have to add a few more classes.
I mean how would you rate Marysville or Livermore for example using this system?
And for that matter how much correction would be needed?
Or would they just be considered as rejects because the errors are impossible to untangle?

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