SAMOS - FSU DAC Quality Evaluation Flags
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FSU DAC Quality Evaluation Flags
A description of FSU DAC quality evaluation flags can be found below. A more detailed description of the quality evaluation process can be found at:

The quality control flags are single alphabetic characters for each data value. Only those variables with a qcindex in the original one-minute data files have flag values (the qcindex is an integer pointer to the flag for a selected variable), i.e. not all meteorological variables are quality controlled. More details on the qcindex can be found in the SAMOS netCDF format document.

Flag Definitions

A Original data had unknown units. The units shown were determined using a climatology or some other method.
B Original data were out of a physically realistic range bounds outlined.
C Time data are not sequential or date/time not valid.
D Data failed the T>=Tw>=Td test. In the free atmosphere, the value of the temperature is always greater than or equal to the wet-bulb temperature, which in turn is always greater than or equal to the dew point temperature.
E Data failed the resultant wind re-computation check. When the data set includes the platform's heading, course, and speed along with platform relative wind speed and direction, a program re-computes the earth relative wind speed and direction. A failed test occurs when the wind direction difference is >20degrees or the wind speed difference is >2.5 m/s.
F Platform velocity unrealistic. Determined by analyzing latitude and longitude positions as well as reported platform speed data.
G Data are greater then 4 standard deviations from the ICOADS climatological means (da Silva et al. 1994). The test is only applied to pressure, temperature, sea temperature, relative humidity, and wind speed data.
H Discontinuity found in the data.
I Interesting feature found in the data. More specific information on the feature is contained in the data reports. Examples include: hurricanes passing stations, sharp seawater 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 passes over land or fixed platform moves dramatically.
M Known instrument malfunction.
N Signifies that the data were collected while the vessel was in port. Typically these data, though realistic, are significantly different from open ocean conditions.
O Original units differ from those listed in the original_units variable attribute. See quality control report for details.
P Position of platform or its movement are uncertain. Data should be used with caution.
Q Questionable - data arrived at DAC already flagged as questionable/uncertain.
R Replaced with an interpolated value. Done prior to arrival at the DAC. Flag is used to note condition. Method of interpolation is often poorly documented.
S Spike in the data. Usually one or two sequential 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 Time duplicate
U Data failed statistical threshold test in comparison to temporal neighbors. This flag is output by automated Spike and Stair-step Indicator (SASSI) procedure developed by the DAC.
V Data spike as determined by SASSI.
X Step/discontinuity in data as determined by SASSI.
Y Suspect values between X-flagged data (from SASSI).
Z Data passed evaluation