BASE
http://ndbc.noaa.gov/

NOTES
<b>Reference:</b> <a href="http://www.ndbc.noaa.gov/NDBCHandbookofAutomatedDataQualityControl2009.pdf" >Handbook of Automated Data Quality Control Checks and Procedures 
of the National Data Buoy Center, 2009.</a>

SENSORS
D; DIR BUOY; Directional Buoy; BASE
N; NON-DIR; Non-directional Buoy; BASE

TESTS
SECTION: TIME SERIES VALUES
D,N;        RANGE CHECK (TS); verify that values fall within established ranges.
SECTION: SPECTRAL VALUES
D,N;        MESSAGE CHECK; verify checksums, parity of transmission.
D,N;        RANGE CHECK (SP); check range of spectral wave density values.
D,N;        TIME CONTINUITY (SP); check continuity of spectral values over 1 hour.
SECTION: PARAMETER VALUES
D,N;        RANGE CHECK (PM); check range of primary and ancillary parameters.
D,N;        TIME CONTINUITY (PM); check continuity of parameter values over time.
D,N;        LOW ENERGY; set parameters to zero for very low energy readings.
D,N;        HEIGHT VS. PERIOD; check that Hs does not exceed limits for the given Ta.
D,N;        WIND/WAVE ENERGY; checks that wave energy corresponds to measured wind.
D;          WIND/WAVE DIRECTION; checks that wave, wind directions correspond.
D;          SWELL DIRECTION; verifies that swell comes from non-sheltered directions.
D;          CHECK FACTORS; range test of directional wave check factors.
D,N;        VISUAL INSPECTION; data quality checks and procedures by analysts.

DETAILS
RANGE CHECK (TS)
Checks that the values of the acceleration or displacement time series fall
within established ranges and that the mean value falls between the minimum
and maximum values of the time series. Data are not released or archived if
the Range Check for Time Series fails.
END
MESSAGE CHECK
Checks that the data encoded for transmission fall within expected ranges, 
that checksums match, and the transmission does not contain parity errors. 
Failure of the Message Check prevents the release and archive of the data.
END
RANGE CHECK (SP)
Checks that the Spectral Wave Densities are within appropriate ranges. 
Failure of the Spectrum Range Check prevents the release and archive 
of the data.
END
TIME CONTINUITY (SP)
Checks that the change within time of the Spectral Wave Densities for 
frequency bands above 0.08 Hz do not change more 0.006f-4 m2/Hz in one 
hour. Data are flagged for further review and released.
END
RANGE CHECK (PM)
Checks that the values for wave parameters, Significant Wave Height 
and Dominant Period are within limits determined by climatology. The 
Range Check for the Significant Wave Height is dependent on the Time 
Continuity check for the previous hour. This dependency prevents the 
Range Check failures during extreme events. Failure of the Range Check 
prevents the release of the data in real-time and will prevent the data 
from being archived unless the failure is removed by an analyst.
<br><br>
Monthly Range Check: Checks that the values for wave parameters, 
Significant Wave Height and Dominant Period, are within limits 
determined by monthly seasonal climatology. Data are flagged for 
further review and released and the data are archived unless rejected 
by analyst.
<br><br>
Ancillary Data Range Checks: Parameters such as buoy tilt, difference 
between the buoy heading determined from the wave system magnetometers 
and the heading from the wind compasses, the directional spreading, 
and the wave system earth magnetic flux are checked to be within 
ranges established by experience. Data are flagged for further 
review and released and the data are archived unless rejected by analyst.
<br><br>
Related Measurement Failure: Significant Wave Height and Dominant Period 
are considered related measurements and the failure of Range or Time 
Continuity checks cause of one causes the failure of the other and thus 
not released and not archived. Significant Wave Height is related to Mean 
Wave Direction (if available) û the failure of Significant Wave height 
causes the failure of Mean Wave Direction, however the failure of Mean Wave 
Direction does not cause failure of Significant Wave Height. Related 
Measurement Failure prevents the release of the data in real-time and 
will prevent the data from being archived unless the failure is removed 
by an analyst.
END
TIME CONTINUITY (PM)
Checks that the change with time of Significant Wave Height are within 
limits determined by climatology. Failure of the Time Continuity Check 
prevents the release of the data in real-time and will prevent the data 
from being archived unless the failure is removed by an analyst.
<br><br>
Monthly Time Continuity: Checks that the change with time of Significant 
Wave Height and Dominant Period are within limits determined by monthly or 
seasonal climatology. Data are flagged for further review and released and 
the data are archived unless rejected by analyst.
<br><br>
Related Measurement Failure: Significant Wave Height and Dominant Period 
are considered related measurements and the failure of Range or Time 
Continuity checks cause of one causes the failure of the other and thus 
not released and not archived. Significant Wave Height is related to Mean 
Wave Direction (if available) û the failure of Significant Wave height 
causes the failure of Mean Wave Direction, however the failure of Mean Wave 
Direction does not cause failure of Significant Wave Height. Related 
Measurement Failure prevents the release of the data in real-time and 
will prevent the data from being archived unless the failure is removed 
by an analyst.
END
LOW ENERGY
If the significant wave height is less than 0.15 m, the Significant Wave 
Height, Dominant Period and Average Period are adjusted to zero and the 
Mean Wave Direction is considered missing.  The Wave Periods are set to 
zero to prevent large swings of periods occurring because of the low 
energy values. Data are flagged for further review and released and the 
data are archived unless rejected by analyst.
END
HEIGHT VS. PERIOD
Wave Height Verses Average Wave Period: Checks whether the Wave Height 
exceeds threshold values (hmax) which are based on a functions of the 
Average Period (AVGPD).  The functions are: 
<br><br>
&nbsp; &nbsp; For AVGPD <= 5 s:
&nbsp; &nbsp; &nbsp; <b>hmax = 2.55 + (AVGPD / 4)</b>
<br><br>
&nbsp; &nbsp; For AVGPD > 5 s:
&nbsp; &nbsp; &nbsp; &nbsp; <b>hmax = (1.16 * AVGPD) - 2</b>
<br><br>
NDBC computes AVGPD as the square root of the ratio of the zeroth spectral 
moment to the second spectral moment. Data are flagged for further review 
and released and the data are archived unless rejected by analyst.
END
WIND/WAVE ENERGY
Wind and Wave Relationship Test: Checks that the wave energy exceeds 
pre-established limits based on the square of a four-hour average wind 
speed. A statistical wind-wave comparison algorithm established a 
relationship between sum of the Spectral Wave Densities at high 
frequencies (0.20 through 0.27 Hz) during the current hour with the 
mean of the square of the wind speeds for the current and the previous 
three hours. Data are flagged for further review and released and the 
data are archived unless rejected by analyst. For further information, 
see Norman Lang, 1987, An algorithm for the quality checking of wind 
speeds measured at sea against wave spectral energy., IEEE J. of OCEAN. 
ENG., OE-12(4), pp. 560-567.
END
WIND/WAVE DIRECTION
Wave Direction Verses Wind Direction Test: Checks that the Mean Wave 
Direction at 0.35 Hz is within 25 degrees of the wind direction when the 
wind speed is greater than 7 m/s, and the wind direction has not varied 
by more than 30 degrees since the previous report, and the Spectral Wave 
Density at 0.35 Hz is greater than 0.003 m2/Hz. Data are flagged for 
further review and released and the data are archived unless rejected by 
an analyst.
END
SWELL DIRECTION
For buoys near the coast, checks that the mean wave directions (alpha1) 
for the frequency bands 0.03 to 0.10 Hz do not originate from sheltered 
or limited fetch directions. Spectral Wave Densities must be both greater 
then 0.5 m2/Hz and at least 5 percent of the Spectral Wave Density of the 
band with the highest Spectral Wave Density. Data are flagged for further 
review and released and the data are archived unless rejected by analyst.
END
CHECK FACTORS
Directional Wave Check Factor:  Range check of the Check Factors at 0.1, 0.2, 
and 0.35 Hz. Data are flagged for further review and released and the data are 
archived unless rejected by analyst.
END
VISUAL INSPECTION
Data Quality Checks and Procedures by Expert Analysts by the National Data Buoy
Center:
<br><br>
Visual inspection may result in the removal of measurements from the archives 
or the restoration of measurements removed by the automated procedures.
<br><br>
<li>Daily: Review time series plots and nearest neighbor comparisons of wave 
  parameters (Significant Wave Height, Dominant Period,  Mean Wave Direction, 
  Wind Wave Height, Period, and Direction, Swell Height, Period, and Direction).</li>
<br>
<li>Monthly: Review plots of the sum of the high frequency Spectral Wave 
  Densities (0.30 through 0.35 Hz) versus square of the average of the four-hour 
  wind speed for stations with 3-meter hulls. For further information, see Palao 
  and Gilhousen, The Re-derivation of the NDBC Wind Wave Algorithm in Ocean Wave 
  Measurement and Analysis, Proceedings of the Second International Symposium, 
  published by the American Society of Civil Engineers, 1993, pp 569-575.</li>
<br>
<li>As needed: Comparison with National Center for Environmental Prediction's 
  WAVEWATCH III wave parameters.</li>
END