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: http://www.coaps.fsu.edu/woce/docs/qchbook/qchbook.htm

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

Flag Description

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.

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 dewpoint temperature.

E Data failed the resultant wind re-computation check. When the data set includes the platform's heading, course over the ground, and speed over the ground 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 difference between the reported and re-computed true wind direction is >20 degrees (or >2.5 m/s for true wind speed).

F Platform velocity unrealistic. Determined by comparing distance travelled between sequential (3-minute interval) latitude and longitude positions. Flags applied to latitude and longitude (not the platform speed).

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 (step) found in the data. Flags assigned to the maximum and minimum points in the discontinuity.

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 Visual inspection shows the value to be erroneous/poor quality. The value should NOT be used.

K Data suspect/use with caution - Applied when the data looks to have obvious errors, but no specific reason for the error can be determined. Some data may be useful, but uncertainty would be high and use is not recommended.

L Oceanographic platform position over land when comparing reported latitude and longitude to ETOPO 1-arc-minute topography dataset.

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 - observation reported as questionable/uncertain in consultation with vessel operator or data arrived at DAC already flagged as questionable/uncertain (use with caution).

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 5 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. (SASSI presently not in use).

V Data spike as determined by SASSI. (SASSI presently not in use).

X Step/discontinuity in data as determined by SASSI. (SASSI presently not in use).

Y Suspect values between X-flagged data (from SASSI). (SASSI presently not in use).

Z Data passed evaluation

Flag	Description
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.
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 dewpoint temperature.
E	Data failed the resultant wind re-computation check. When the data set includes the platform's heading, course over the ground, and speed over the ground 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 difference between the reported and re-computed true wind direction is >20 degrees (or >2.5 m/s for true wind speed).
F	Platform velocity unrealistic. Determined by comparing distance travelled between sequential (3-minute interval) latitude and longitude positions. Flags applied to latitude and longitude (not the platform speed).
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 (step) found in the data. Flags assigned to the maximum and minimum points in the discontinuity.
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	Visual inspection shows the value to be erroneous/poor quality. The value should NOT be used.
K	Data suspect/use with caution - Applied when the data looks to have obvious errors, but no specific reason for the error can be determined. Some data may be useful, but uncertainty would be high and use is not recommended.
L	Oceanographic platform position over land when comparing reported latitude and longitude to ETOPO 1-arc-minute topography dataset.
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 - observation reported as questionable/uncertain in consultation with vessel operator or data arrived at DAC already flagged as questionable/uncertain (use with caution).
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 5 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. (SASSI presently not in use).
V	Data spike as determined by SASSI. (SASSI presently not in use).
X	Step/discontinuity in data as determined by SASSI. (SASSI presently not in use).
Y	Suspect values between X-flagged data (from SASSI). (SASSI presently not in use).
Z	Data passed evaluation