Outline of Quality Control Flags
Shawn R. Smith
WOCE Surface Meteorology DAC
Center for Ocean Atmospheric Prediction Studies
Florida State University
The quality control flags are single alphabetic characters for each data
value indicating quality of that specific value. Only those variables with a
qcindex have flag values (the qcindex is an integer pointer to the flag for
a selected variable). The flags are:
A Original data had unknown units. The units indicated were
determined using a climatology or other method.
B Original data was out of the range bounds outlined (Table 1).
C Time data are not sequential or date/time not valid.
D Data failed T�Tw�Td test.
E Data failed resultant wind recomputation check. When the
original data set includes the platform's speed and direction
along with the platform relative wind speed and direction,
recomputed earth relative wind speed and direction and compared to
the reported earth relative wind speed and direction. A failed
test occurs when the wind direction difference is > 10 degrees
or the wind speed difference is >5 m/s.
F Platform velocity unrealistic. Determined by platform position
and speed data.
G Data are greater than 4 standard deviations from the monthly
climatological means in the da Silva et al. (1994) COADS
climatology. The test is only applied to pressure, temperature,
sea surface temperature, relative humidity, and wind speed data.
H Discontinuity found in data
I Interesting feature found in data. More specific information on
the feature is contained in the data reports. Examples include:
hurricanes passing station, sharp sea water temperature gradients,
strong convective events, etc.
J Data are of poor quality by visual inspection, DO NOT USE.
K Data suspect/use with caution - this flag applies when the data
look to have obvious errors, but no specific reason for the error
can be determined.
L Oceanographic platform passed over land/fixed platform moves
dramatically.
M Known instrument malfunction.
N Flag currently not used.
O Flag currently not used.
P Position of platform or its movement are uncertain. Data should
be used with caution.
Q Flag currently not used.
R Flag currently not used.
S Spike in the data. Usually one or two data values (sometimes up to
4 values) that are drastically out of the current data trend.
Spikes occur for many reasons including power surges, typos, data
logging problems, lightning strikes, etc.
T Flag currently not used.
U Flag currently not used.
V Flag currently not used.
W Flag currently not used.
X Flag currently not used.
Y Flag currently not used.
Z Data passed evaluation
Table 1: Range Bounds For Determining Use of Flag 'B'
Variable Lower Bound Upper Bound Units Other
---------------------------------------------------------------------
time 1-1-1980 12-31-1999
latitude -90 90 degrees
longitude 0 359 degrees
platform heading 0 359 degrees
platform speed 0 15 m/s research vessels
0 0 m/s stationary buoys
0 2 m/s drifters
plat. wind direction 0 360 degrees
plat. wind speed 0 40 m/s
wind direction 0 360 degrees
wind speed 0 40 m/s
pressure 950 1050 mb Sea level
air temperature -10 40 deg Celsius
wet bulb temperature -10 40 deg Celsius
dew point temperature -10 40 deg Celsius
sea temperature 0 35 deg Celsius
relative humidity 0 100 percent
radiation 0 1400 W/m2
Reference:
da Silva, A. M., C. C. Young, and S. Levitus, 1994: Atlas of
Surface Marine Data, Volumes 1: Algorithms and Procedures. NOAA
Atlas Series. In press.