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Cooperative Data Network (COOP)
Data Measurement and Quality Flags


A N Accumulated amount since last measurement.
B N Accumulated amount includes estimated values (since last measurement).
E N Estimated (see Table "G" for estimating method).
J N Value has been manually validated.
M Y For fixed length records only. Flag1 is "M" if the data value is missing. In this case, the sign of the meteorological value is assigned "-" and the value of the meteorological element is assigned "99999".
S N Included in a subsequent value. (data value = "00000" OR "99999").
T N Trace (data value = 00000 for a trace).
( N Expert system edited value, not validated.
) N Expert system approved edited value.
Blank N Flag not needed.

An original observation that is followed by an edited observation is indicated by "2" in Flag 2.

Flag 1 values of "S" and "A" usually occur in pairs (ie. a daily value will have Flag 1 assigned as "S" and the next daily value will have Flag 1 assigned as "A"). For some daily values these flags do not occur in pairs. Other values occasionally appear in Data Measurement Flag 1 for which documentation is not currently available, e.g., "C" and "s".


0 N Valid data element.
1 N Valid data element (from "unknown" source, pre-1982).
2 Y Invalid data element (subsequent value replaces original value).
3 Y Invalid data element (no replacement value follows).
4 N Validity unknown (not checked).
5 N Original non-numeric data value has been replaced by its deciphered numeric value.
A Y Substituted TOBS for TMAX or TMIN
B^ Y Time shifted value
C N Precipitation estimated from snowfall
D Y Transposed digits
E Y Changed units
F Y Adjusted TMAX or TMIN by a multiple of + or -10 degrees
G Y Changed algebraic sign
H Y Moved decimal point
I Y Rescaling other than F, G, or H
J Y Subjectively derived value
K Y Extracted from an accumulated value
L Y Switched TMAX and/or TMIN
M Y Switched TOBS with TMAX or TMIN
N+ Y Substitution of "3 nearest station mean"
O Y Switched snow and precipitation data value
P Y Added snowfall to snow depth
Q Y Switched snowfall and snow depth
R N Precipitation not reported; estimated as "O"
S* Y Manually edited value
T Y Failed internal consistency check
U Y Failed areal consistency check (beginning Oct. 1992)
V Y Replacement value based on TempVal QC process (beginning Feb. 2006)

* Manually edited value could be derived by any of the procedures noted by Flags A-R.

+ Starting with the January 2002 data month, the .3 nearest station mean. value is derived by NCDC.s spatial quality control algorithm named TempVal. This value is based on ASOS/AWOS/CRN grids summarized for each reader group, AM (at 0800), PM (at 1600), and Midnight (at 2400). Starting with the August 2004 data month, the ASOS/AWOS/CRN grids are based on hourly temperature values. The use of the hourly grids allows the quality control algorithm to compare COOP grids properly with the ASOS/AWOS/CRN grids based upon the observer.s reported observation time. Starting with the Feb 2006 data month, TempVal edits will use the .V. flag.

^ Beginning with the January 2003 data month, the TempVal algorithm began to detect shifters. Some shifters may be manually detected.

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