Towards a Standard for Real-time Quality Control Procedures for in situ Ocean Waves Richard Bouchard 1 and Julie Thomas 2 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) 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) NOAA/National Data Buoy Center (QC) 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:

TIME SERIES (Raw Calibrated Data) CategoryCriteriaOrderFlagAction Data GapsConsecutive N missing data. Maximum number of missing data. 1SoftN is user defined. Include in % count. SpikesUser defined Points >= M*std with P iterations 2SoftInterpolate/extrapolate up to N points. N is user defined. M can be user defined, recommended M=4. Include in % count. Range testLocation, instrument defined.2 Max/min user defined. 1. Soft1. Interpolate/extrapolate up to n points. N is user defined. Include in % count. 2. Hard2. Instrument spec exceeded, reject. Mean shift (segments) A mean shift "P" occurs in this time series. 3HardReject entire record. P is user defined. Acceleration testUser defined (a>M*g)3SoftRecommended M<=1/2. Interpolate/extrapolate up to N points. N is user defined. Include in % count. Mean test, variance test User defined, location dependent 4Soft/HardFlag/Reject if exceeds threshold. Percent points goodCheck for M% good data (based on above 6 criteria) 5HardRecommended M>=90%

PARAMETER VALUES: Height, Period, Direction, Spreading CategoryCriteria OrderOrder FlagAction Wave parameters max/min/acceptable range (H,T,D,S) Location dependent 1 1. Hard 2. Soft User defined limits. 1. Gross or Global Limit(s): Reject entire record if H exceeds limit otherwise reject individual parameter. 2. Narrower Seasonal/Location limits – flag. Time continuity Short range history (applied to H) 2SoftUser defined

SPECTRAL VALUES CategoryCriteria OrderOrder FlagAction Operational frequency range test *defined by the environment and instrument 1 1. Soft 2. Hard 1. Max/min User Defined 2. Instrument spec. exceeded, reject. Incident low frequency energy direction Location defined 1SoftUser Defined Check Factors, Ratio Should be approximately = 1, check over time. Location dependent 2SoftUser Defined

Submitted to IOOS Data Management and Communications Steering Team as a Possible IOOS Standard Submitted standard can be viewed at: (login required), or 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, Krogstad, H.E., Steele et al UNESCO, Check 3.2.4, Check Factor. USACE FRF, Current Usage CDIP, USACE FRF, and NDBC.

Contacts Richard Bouchard, NOAA/NDBC Julie Thomas, CDIP Anne Ball, DMAC ST