Scripps High Resolution XBT Network: QA/QC Procedures

Dean Roemmich, Lisa Lehmann, and Glenn PezzoliScripps Institution of Oceanography

CLIVAR-GSOP Coordinated Quality-Control of Global Subsurface Ocean Climate Observations

June 2013

Outline• SIO 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 Program• Started March 1986 on a single line: PX06 (Fiji-Auckland, NSF). Expanded during WOCE

to cover the Pacific and South Indian Oceans• To 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:

o Final QC’d, no metadata, no QC class or codes ~ 55,000 (1986~2001)o Final QC’d with metadata, class, codes ~ 10,000 (2009~2012)

• XBT delayed-mode data close to submission:o Final QC’d, metadata, class, codes inclusion in various stages ~ 12,000

• Data manager is re-QC’ing 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.

Data quality begins at sea

• XBTs 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 sea

• Experienced ship-riders oversee data collection at sea, so problems are discovered and addressed rapidly.

• Efforts are made to use XBT’s 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 1999

PX31(PX09) Oct 2009

Steps in Delayed-mode Quality Control

• Read ship-rider report• Check for and remove false splashes (nearly eliminated since 2010)• QC data utilizing:

1. Neighboring profiles2. Climatology based on buddy profiles3. Individual buddy profiles4. Regional oceanographic features

• Re-navigate position based on previous and post GPS location• Add metadata to QC’d data• At 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: Edit data

• Add QC codes following “CSIRO Marine Labratories Report 221, Quality Control Cookbook for XBT Data” specifications.

• Edit 2m vertically averaged data using SIO’s XBT editor “wexbt” to create SIO’s “e” files (final QC’d 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 profiles

This 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 342 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: Buddies

Profile 170 (bottom, black) appears to veer warm toClimatology.. However…

PX10 January 2004220 profiles used to create climatology

Delayed-mode QC: Buddies

PX10 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. We’ll call this a PIA (Inversion Probable)

Shown with PX10 February 1994

Shown 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 2008

PX37 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 1996

At 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: Add metadata Additional metadata added to SIO’s final QC’d ‘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 SN’s. These are also being added to the “e” files as Class 2 (probably good). A master SIO XBT SN & DoM list is continually updated and checked against for duplicates.•Autolauncher tube number or Hand launcher: May be used to track and correct possible errors due to particular tube.•Drop coefficients: Using WMO code table 1770. To maintain a consistent dataset, SIO’s ‘e’ files use the original Sippican coefficients for Deep Blue’s (code 051).•Autolauncher height to water: Measurements began mid-2012. One average number is kept for each cruise. Past cruises will be estimated from ship pictures. Riders report that height can vary up to 2 m during cruise.•Ship callsign

Sample SIO ‘e’ file:

Line1:Drop number = 256 Instrument type = 051 (WMO Code table 1770)Recorder type = 06 (WMO Code table 4770)Ship callsign = A8KC6Latitude = 27.668Longitude = 222.827Autolauncher tube number = 3

Line 2:Drop date (dd-mm-yyyy) = 25-03-2013Drop GMT time = 20:26:36SEASID = 9256F2DFProbe serial number = 1157773Probe Date of Manufacture (mm-dd-yyyy) = 12-09-2010

Lines 3-end:Depth in 2 meter increment samplingsTemperature in degrees C (multiply by 0.001)QC Class (CSIRO Marine Lab Report 221)QC Code (if feature marked)Original data if QC Class=5 (Changed)

Additional metadata

SIO archives additional metadata not included in “e” file:• Equipment calibrations are done pre and post (and sometimes mid) cruise

to identify problems.• Navigation data: one minute averages of GPS data cataloged since late

1991.• Weather observations: Hand written, 6 times a day, rider observations of

wind direction and force, air and sea surface temperature.

Future directions: XBT and Argo• High Resolution XBT transects and Argo are a valuable combination scientifically

for observing western boundary currents and estimating the time-varying heat transport and storage in large ocean regions (e.g. Zilberman et al., 2013, Douglass et al., 2010, DSR II).

• Need to identify and remove systematic errors (fall-rate, wire-related problems) for consistency of the datasets.

• Argo will be useful in quality control of HRX data by providing: Global climatologies of temperature and its variability (e.g. Roemmich and

Gilson, 2009, Progress in Oceanography). Across-track gradients to enable comparison along non-collinear HRX ship

tracks.

All ship tracks have some variability. Argo provides the spatial context.

Argo mean temperature (contours) and standard deviation (colors) at 700 dbar