1. NDBC Real Time Wave Data Processing and QC/QA
Chung-Chu Teng
National Data Buoy Center
Stennis Space Center, MS 39529, USA

2. NDBC Wave Stations
88 buoys (28 directional waves) and 4 C-MAN stations

3. NDBC wave measurement capabilities
Non-directional waves
Directional waves
3-m, 10-m discus buoys
Yes
(all)
(28)
6-m NOMAD buoys
Plan to use a supplemental directional wave buoy
C-MAN
(in water)
Yes (4, not very reliable)
Plan to use COTS wave sensors or a directional wave buoy
(on land) --
Plan to use a directional wave buoy

4. C-MAN Wave Measurements
Chesapeake Light
Diamond Shoal
St. Augustine

5. Buoy Wave Measurements
6-m NOMAD buoy
3-m discus buoy
10-m discus buoy

6. New Stand-alone Wave System/Buoy
Directional Wave Measurement System:
- Small & light
Low power consumption
Low cost
Built-in transmitter
Standalone
Configurable
Directional Wave buoy:
Small & light, deployable from small vessels
Low cost
Low maintenance
1.8 m COLOS buoy

7. NOMAD Directional Wave Measurements
Use a small directional wave buoy (tether to a 6-m NOMAD buoy or stand-alone)
GOES or Iridium
RF/LOS
communication

8. C-MAN Wave Measurements
GOES or Iridium
RF/LOS
communication
Deploy a stand-alone directional wave buoy
Install a fixed directional wave sensor on the structure

9. Nondirectional wave data
Wave energy spectrum
Wave parameters:
Peak (or dominant) wave period, Tp
Mean (or average) wave period, Tz or Ta
Significant wave height, Hs
S(f)
Frequency, f

10. Buoy Wave Measurement Ocean waves Buoy hull motions
Measurements (Sensors)
Onboard processing
Transmission (or storage)
Shoreside processing
Wave data

11. Nondirectional wave data from buoys
From buoy motion to wave data
Sh(f): spectrum of buoy heave motion
Sw(f): wave spectrum (acceleration)
PTF: power transfer function
From acceleration to displacement spectra

12. Noise Correction
S(f)
Low-frequency
noise
Frequency (f)

13. NDBC directional wave buoy systems
Based on the “slope following” principle
Can only use axis-symmetrical buoys
Buoy pitch and roll information are required to determine directional wave data

14. Directional wave algorithm (1)
f : wave frequency; 2 : wave direction
1: vertical motion (heave)
2: N-S slope (pitch)
3: W-E slope (roll)
K: the wave number
C and Q : co- and quad-spectra

15. Directional wave algorithm (2)
θ 1 and θ2: mean and principal wave directions
r1 and r2 : directional energy spreading

16. Configurations of NDBC directional wave systems
HIPPY – a gimbaled gyro system that measure pitch and roll directly
MO – use only magnetometer outputs to estimate buoy pitch and roll
ARS – derive buoy pitch and roll from angular rate sensors

17. NDBC Wave Systems DACT Wave Analyzer (WA)
DACT Directional Wave Analyzer (DWA)
VEEP Wave Analyzer (WA)
Wave Processing Module (WPM)
Directional Wave Processing Module (DWPM)
Non-Directional Wave Processing Module (NDWPM)
Directional Wave Measurement System (DWMS)

18. General Principles for Data QA/QC
Reasonability:
Data should be in reasonable ranges and intervals.
Continuity:
Data should maintain the continuity in time and space.
Consistency (or correlation):
Data should have proper time correlation, spatial correlation, and correlations with other measurements.

19. Some wave data QC techniques
Range check
Time continuity
Internal consistency (e.g., QMEAN)
Wind vs. wave energy (wind-wave algorithm)
Swell direction check
High frequency spectral spikes,
Wave height vs. average wave period
Wave direction vs. wind direction (> 0.35 Hz)
When needed, wave data from NCEP’s wave models and other organizations will be used to check its buoy wave data.

20. Hard Flags (by hierarchy - highest to lowest)
T Transmission parity error (Applies to continuous winds and non-WPM wave data)
M Missing sensor data (A result of a garbled or missing message).
W A WPM wave message is short, missing a checksum, or parity errors are detected.
E Calculation limits are exceeded or are in error (waves only, flags WVHGT).
D Delete measurement from release and archive (A Data Analyst or automated QC has failed the sensor).
S Invalid statistical parameter (in waves, QMEAN is not between QMIN and QMAX, flags WVHGT).
V Failed time continuity.
L Failed range limits.
H Hierarchy reversal has occurred (BARO, WSPD, WDIR only).
R A related measurement has failed a hard QC check.

21. Soft Flags (in alphabetical order)
a Measurement is above monthly, regional limit.
b Measurement is below monthly, regional limit.
c Measurement has been adjusted, or corrected (applies to DEWPT and WVHGT, DOMPD and AVGPD).
d Failed standard deviation test (continuous winds only).
f Measurement failed hourly time continuity.
g Failed gust-to-mean wind speed ratio (applies to standard and continuous winds).
i Continuous and hourly wind speeds don’t agree.
j One, and only one, transmission error detected in the continuous wind string of a GOES message (all continuous wind measurements are flagged, if more than one error detected, than flag is upgraded to a T flag).
k Difference between duplicate measurements is too high.
m High frequency spikes detected in the wave spectrum (C11), WVHGT is flagged.
n Measurement failed comparison with NCEP model fields.
p Failed wave height to wave period comparison test.
q Swell direction is from an improbable direction.
r Related measurement failed (continuous winds only).
s Stuck raw compass ( RCOMP and WDIR are flagged).
t Tendency difference between duplicate sensors is too high.
v Failed relative humidity verses visibility check.
w Failed wind direction verses wave direction check.
x Wind wave energy is too high for prevailing wind speed.
y Wind wave energy is too low for prevailing wind speed.
z Failed bow azimuth verses wind direction check.

22. NDBC Technical Document 03-02
Handbook of Automated Data Quality ControlChecks and Procedures of the National Data Buoy Center
February 2003
National Data Buoy Center
Stennis Space Center, Mississippi

23. Range check (wave height)
Previous EQC limit: 5.2 m (Lakes Erie and Huron)
New EQC limit: 7.5 m

24. Range check (wave period)

25. Increasing QMEAN

26. Hurricane Ivan - Significant wave heights

27. Significant wave height during Ivan

28. Wind and wave directions

29. Wind-wave algorithm

30. How is your wave measurement?

31. We always improve our systems and DQC/QA process so we can get more accurate wave measurement