Scripps High Resolution XBT Network: QA/QC ProceduresDean Roemmich, Lisa Lehmann, and Glenn PezzoliScripps Institution of Oceanography
CLIVAR-GSOP Coordinated Quality-Control of Global Subsurface Ocean Climate ObservationsJune 2013
OutlineSIO High Resolution Network, 1986-2013.Data quality begins at sea.Delayed-mode quality control.Future directions.The SIO High Resolution XBT Program presently deploys ~5000 XBTs per year, as part of the global HRX partnership.
The SIO High Resolution XBT ProgramStarted March 1986 on a single line: PX06 (Fiji-Auckland, NSF). Expanded during WOCE to cover the Pacific and South Indian OceansTo date ~103,000 good XBT profiles during ~450 (manned) cruises, with 4 cruises sailing this June.Sparse XCTDs are were also obtained (pre-Argo) for T/S relation.Support transitioned from NSF to NOAA in 1990s 2000s.Partnerships: CSIRO, NOAA/AOML, Tohoku U, NIWA, and others.Data submitted in near real-time (latency has decreased over the years).XBT delayed-mode data submitted to NODC:Final QCd, no metadata, no QC class or codes ~ 55,000 (1986~2001)Final QCd with metadata, class, codes ~ 10,000 (2009~2012)XBT delayed-mode data close to submission:Final QCd, metadata, class, codes inclusion in various stages ~ 12,000Data manager is re-QCing remaining (~ 26,000) profiles to add QC Class and Code, and attach metadata.Time permitting, we will add QC Class and Code, and metadata to previously submitted data for resubmission to NODC.
SIO HRX Cruises (03Jun2013)
`Total` may contains Test ProbesGood may not reflect re-QCd numbersp31 listed here had SIO riderNot included: p34 & i28
LineRatioTotalGoodNcruiseBegin YearEnd Years3798.3922362200222008Continuingp0597.9941234040162009Continuingp0696.72109710611820092010p0897.60509049682020042009p0995.2427158258641161986Continuingi1597.35100009735401994/20031995/Continuinga2285.97807569421061996Continuingp3198.6411751159131991Continuingp3795.3426052248378319912011p3890.5359995431531993Continuingp4097.2257555932012Continuingp5094.3911047104274119932008p8193.08677963102819972004Total94.63109406103533559
Data quality begins at seaXBTs are deployed from a stern-mounted autolauncher, resulting in many fewer wire problems than bridge-launching. The autolauncher can be re-positioned at sea according to conditions.Probes in the autolauncher stay close to SST, minimizing temperature bias seen in heated or cooled probes.Routine calibration using high precision resistors (test cannister) identifies problems occurring anywhere from the MK21 to the autolauncher (electronics, cables, and connectors).Immediate automated checking compares each profile with the previous profile, alerting the ship-rider to failures and unusual features for quick re-drops.
Data quality begins at seaExperienced ship-riders oversee data collection at sea, so problems are discovered and addressed rapidly.Efforts are made to use XBTs from same batch. XBT serial number and date of manufacture are recorded.Autolauncher/Handlauncher height to water recorded throughout cruise.Using up-to-date SIO XBT database, ship-rider does preliminary QC while weather and conditions are current.
Data quality begins at sea: re-drops.Eastern subtropical North Pacific: Drop 44 (red) is quite different from 43 (gray) and earlier profiles. A re-drop 45 (green) about 2 km along-track shows that 44 is good, with subsequent drops filling in the transition. Tropical North Pacific:Drop 182 (black) is quite different from 181 (blue) and earlier profiles. A re-drop 183 pink) about 2 km along-track confirms that 182 is bad.PX37 July 1999PX31(PX09) Oct 2009
Steps in Delayed-mode Quality Control
Read ship-rider reportCheck for and remove false splashes (nearly eliminated since 2010)QC data utilizing:Neighboring profilesClimatology based on buddy profilesIndividual buddy profilesRegional oceanographic featuresRe-navigate position based on previous and post GPS locationAdd metadata to QCd dataAt present, delayed-mode QC for new cruises is done within 1 month.
Delayed-mode QC: Read Ship-rider report
Important to understand cruise and weather conditions. Eastern subtropical North Pacific: Drop 001 (gray) shows record rain runoff. If ship-rider did not document that fact, I would have considered the surface suspect. The following profiles also show deeper mixed layer than in previous transects, likely due to huge swells in area during this time.PX37 South, January 2010
Delayed-mode QC: Remove false splashesFalse splashes (aka Premature Launch) are caused by ground faults in the wiring, which are often caused by moisture in the equipment. Our ship-riders are trained to detect and fix problems as they occur, thus ensuring a cleaner dataset. Our standard operating procedure utilizes desiccant packs inside electronic equipment, which has nearly eliminated all false splashes. We run the rare profiles with false splashes through an operator driven filter which shows the raw ascii data and allows us to choose the actual splash. We overlay the re-created profile with its neighbors and climatology to determine if the data is good.Profile 44 (red) shows false splash detectProfile 44 (red) after removing false splashRemington desiccant packs are easily recharged & come with saturation/desiccation indicators.
Delayed-mode QC: Edit dataAdd QC codes following CSIRO Marine Labratories Report 221, Quality Control Cookbook for XBT Data specifications.Edit 2m vertically averaged data using SIOs XBT editor wexbt to create SIOs e files (final QCd XBT data).wexbt enables user to mark features (good and bad), and interpolate through spikes.A raw data (0.1 second temperature readings) viewer can also be used to help identify fine scale features.All data (good/bad/original-if-interpolated) is stored in e file.
Delayed-mode QC: Neighboring profiles
Important to realize best source of QC information for each profile in high resolution sampling is the neighboring profiles.
This sequence shows the temperature inversion at the base of the mixed layer just north of Fiji. PX09 Oct 2009
Delayed-mode QC: Neighboring profilesThis cluster of neighbors in the Kuroshio illustrates how closely spaced profiles (~15 km apart) reveal the highly structured character of the temperature field in a strong current.PX44 January 2009
Delayed-mode QC: ClimatologyWe use a climatology developed from the HRX transects for many checks. Here it is used to determine where profile 247 (Top, green) went bad. Profile 247 (Bottom, black) iscompared to climatology. It appears to have gone bad at 600 m, where it veers abruptly warm to climatology.PX37 June 2008 Profiles from variousPX37 transects within 1 degree latitude and longitude to createclimatology.
We can view buddies of a profile individually to see if a particular feature has been seen in the past (or future). Profile 170 (Top, red). Is that an inversion or wirestretch at 580m?Delayed-mode QC: BuddiesProfile 170 (bottom, black) appears to veer warm toClimatology.. HoweverPX10 January 2004220 profiles used to create climatology
Delayed-mode QC: BuddiesPX10 January 2004-Profile 170 (black, all 3 figures) is shown with buddies from different cruises. We can find many profiles that match it very well over time. Well call this a PIA (Inversion Probable) Shown with PX10 February 1994Shown with PX10 April 2003Shown with PX10 August 1995
Delayed-mode QC: Regional features
If a feature (top: profile 027 in black, bottom: profile 036 in black) is not present in neighboring profiles and does not have a close geographical buddy in past cruises, then consider regional oceanographic features.PX37 Feb 2008PX37 Nov 2008
Delayed-mode QC: Regional featuresThis (top, right) and other previous transects show confirmed eddies in the region of the previous two unconfirmed profiles. Therefore we consider the two profiles on the previous slide as good data (class 1).PX37 Jul 1996At right, a very similar feature, occurring nearby in a CTD transect at 37oN, 128oW, was described as a California Undercurrent eddy by Cornuelle et al (2000, JGR, 105, 1227-1243.)
Delayed-mode QC: Re-navigate XBT drop positionImportant to get an accurate position fix on drops.We create a ship transect navigation file. It consists of one minute averages of incoming GPS positions (approximately 20 fixes/minute).Drop is originally stamped with current (one) GPS position.Delayed-mode: re-navigate each drop position using XBT probes date/time stamp and navigation files previous and post average GPS positions.
Delayed-mode QC: Add metadata Additional metadata added to SIOs final QCd e file (submitted to NODC):SEASID: unique identifier created shipboard by Amverseas on raw binary message, and stored within binary message. XBT serial number and Date-of-Manufacture: Since early 2012 SIO riders carefully catalog SN & DoM resulting excellent quality. Prior to 2012 SIO riders cataloged order of XBT cases (SN & DoM) used during cruise, or tables of drop numbers matched to SNs. These are also being added to the e files as Class 2 (probably good). A master SIO XBT S