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Towards a Standard for Real-time
Quality Control Procedures for in situ
Ocean Waves
Richard Bouchard1 and Julie Thomas2
1. NOAA’s National Data Buoy Center
2. Coastal Data Information Program/Scripps Institution of Oceanography
Presented at
QARTOD to OGC (Q2O)
February 2008
Photo courtesy of NWS Portland, OR
Motivation for Standard
• Need simple, proven, and consistent
quality descriptions as more new
observing systems arise and more
observations are exchanged and
integrated
• Real-time -> users need an expected level
of quality assurance for rapid assimilation
and application
Procedures Development
• Quality Assurance of Real-Time
Oceanographic Data (QARTOD) -
http://www.qartod.org
• Sponsored by NOAA
• Four workshops 2003 – 2006 and the
Waves Technical Workshop – 2005
• Waves Working Group – government,
academia, commercial, research,
operational
Proven Practices
• Coastal Data Information Program (CDIP)
http://cdip.ucsd.edu/?nav=documents&sub=index&xitem=proc#quality
• NOAA/National Data Buoy Center
http://www.ndbc.noaa.gov/handbook.pdf (QC)
http://www.ndbc.noaa.gov/wavemeas.pdf
• US Army Corps of Engineers, Nortek,
SonTek/YSI, Teledyne RDI
• UNESCO/IOC/IODE & MAST, 1993: Manual of
Quality Control Procedures for Validation of
Oceanographic Data – useful, but dated
Series of Tests
• Tests applied to the:
– Time Series,
– Wave Spectra, and
– Bulk Parameters (e.g., height, period)
• Flagging convention: QC indicator
– Hard flag stops the release of data
– Soft flag is warning
– Some parameters have tests with both hard and soft flagging
criteria
– Original flag coding abandoned – at odds with existing
conventions
• QARTOD Results and Proven Practices:
http://cdip.ucsd.edu/qartod/waves_qc
TIME SERIES (Raw Calibrated Data)
Category Criteria Order Flag Action
Data Gaps Consecutive N missing data. 1 Soft N is user defined. Include in %
Maximum number of missing count.
data.
Spikes User defined Points >= M*std 2 Soft Interpolate/extrapolate up to N
with P iterations points. N is user defined. M
can be user defined,
recommended M=4. Include in
% count.
Range test Location, instrument defined. 2 Max/min user defined.
1. Soft 1. Interpolate/extrapolate up to
n points. N is user defined.
Include in % count.
2. Hard 2. Instrument spec exceeded,
reject.
Mean shift A mean shift "P" occurs in this 3 Hard Reject entire record. P is user
(segments) time series. defined.
Acceleration test User defined (a>M*g) 3 Soft Recommended M<=1/2.
Interpolate/extrapolate up to N
points. N is user defined.
Include in % count.
Mean test, variance User defined, location 4 Soft/Hard Flag/Reject if exceeds
test dependent threshold.
Percent points good Check for M% good data 5 Hard Recommended M>=90%
(based on above 6 criteria)
PARAMETER VALUES: Height, Period, Direction, Spreading
O
r
Category Criteria d Flag Action
e
r
User defined limits.
1. Gross or Global Limit(s):
Reject entire record if H
Wave parameters 1. Hard
Location exceeds limit otherwise
max/min/acceptable 1 2. Soft
dependent reject individual
range (H,T,D,S)
parameter.
2. Narrower Seasonal/Location
limits – flag.
Short range
Time continuity history 2 Soft User defined
(applied to H)
SPECTRAL VALUES
O
r
Category Criteria d Flag Action
e
r
*defined by
Operational the 1. Soft 1. Max/min User Defined
frequency range environment 1 2. Hard 2. Instrument spec. exceeded,
test and reject.
instrument
Incident low Location
frequency energy 1 Soft User Defined
direction defined
Submitted to IOOS Data
Management and Communications
Steering Team as a Possible IOOS
Standard
Submitted standard can be viewed at:
https://ioosdmac.fedworx.org (login
required), or
http://nautilus.baruch.sc.edu/twiki/bin/view/Main/WaveQC
QARTOD Results Refined by
– Response to Request for Comments
– DMAC ST Standards Requirements
– Comments from DMAC Steering Team
Detailed Description: Check Ratio
Scope or Applicability: Heave/Slope (pitch and roll) Buoys.
Description
The check ratio or check factor, R, is loosely defined as the ratio of vertical to horizontal wave
orbital motions. R is more formally defined by:
where:
C11, C22, and C33 are the cross-spectra respectively of heave, pitch, and roll.
k is the wave number,
h is the water depth, and
tanh is the hyperbolic tangent function.
This check ratio is a function of frequency and depth. It should theoretically be 1 for relatively
deep water waves, but tends to deviate substantially from that value at periods longer than the
peak frequency, and at short periods outside the response range of the buoy.
The data provider may choose any of the following methods of the check ratio test:
– Computed at the peak wave energy period and at a short period (but within the surface-following capability
of the buoy) flag values outside the range of 0.9 to 1.1, or
– Test at least three frequencies distributed one each in the low, mid, and high frequency ranges, or
– Compute the percentage of all frequencies whose check ratio is within acceptable limit of 1.0, and flag if
the percentage is outside of an established criterion.
Sources:
CDIP, 2003.
Krogstad, H.E., 2001.
Steele et al. 1992.
UNESCO, 1993. Check 3.2.4, Check Factor.
USACE FRF, 2007.
Current Usage
CDIP, USACE FRF, and NDBC.
Contacts
• Richard Bouchard, NOAA/NDBC
richard.bouchard@noaa.gov
• Julie Thomas, CDIP
jot@cdip.ucsd.edu
• Anne Ball, DMAC ST
anne.ball@noaa.gov
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