From: National Climatic Data Center
      U.S. Climate Reference Network Program

Re:   Surface Temperature (Infrared) Calibration Revision

Due to an ongoing equipment refresh to a new infrared surface temperature sensor model,
USCRN is now also reporting corrected surface temperature measurements for some stations.
These changes will impact previous users of the data because the corrected values will 
differ from uncorrected values.

To distinguish between uncorrected (raw) and corrected surface temperature measurements,
a surface temperature type field will be added to the daily01 product. This new field 
will be one character in length and will immediately precede the existing surface 
temperature fields. For the daily01,  the new field will be inserted at column 88, with
any following fields shifted forward by 2 characters.

The possible values of the new field will be "R" to denote raw surface temperature 
measurements, "C" to denote corrected surface temperature measurements, and "U" for 
unknown when measurements are missing.

This change will be made effective on Monday, January 7, 2013, at approximately 1500 
Coordinated Universal Time (UTC).