The Harvest Experiment: Calibration of the 16-yr Climate Date Record from TOPEX

1. The Harvest Experiment: Calibration of the 16-yr Climate Date Record from TOPEX/Poseidon, Jason-1 and OSTM Bruce Haines and Shailen Desai Jet Propulsion Laboratory, California Inst. of Tech., Pasadena CA George Born University of Colorado, Boulder Steve Gill NOAA National Ocean Service, Silver Spring MD

2. October 27, 2008 Ocean Platforms Workshop Ocean Surface Topography Mission(OSTM)/Jason-2 Science Objectives: With T/P and Jason, determine the variability of ocean circulation at decadal time scales Provide estimates of significant wave height and wind speeds over the ocean Increase understanding of ocean circulation and seasonal changes Improve forecasting of climate events like El Ni�o Measure global sea-level change What is needed from the measurement system? Accurate geocentric sea-surface height measurements Requirement of 4.2 cm RMS; goal of 2.5 cm RMS. Precise Orbits Requirement of 2.5 cm RMS; goal of 1.0 cm RMS.

4. October 27, 2008 Ocean Platforms Workshop Typical Data Coverage (1 repeat cycle = ~10 days)

5. October 27, 2008 Ocean Platforms Workshop Motivation How do we best calibrate sea-level record at the 1 mm/level? Geographically correlated errors in both the bias and rate What are the sources of the errors?

6. October 27, 2008 Ocean Platforms Workshop Harvest PlatformOwned by Plains Exploration and Production (PXP) Open-ocean verification site located 10-km off coast of central California Ground track passes directly through this location by design (T/P heritage). Provides independent measure of local geocentric sea level. Precise GPS receiver Redundant tide gauges Local survey Yields absolute SSH bias. Also provides form monitoring of ancillary parameters (e.g., wet troposphere delay). Rich in-situ data set representing over 16 years of continuous monitoring. Jason-1 and OSTM now overflying platform in formation Tandem verification phase 54-s separation

7. October 27, 2008 Ocean Platforms Workshop Altimeter Calibration Schematic

9. October 27, 2008 Ocean Platforms Workshop Map of Harvest Vicinity

10. October 27, 2008 Ocean Platforms Workshop Harvest Conditions Typical of Open Ocean

11. October 27, 2008 Ocean Platforms Workshop High Sea States Impact Tide-Gauge Data Two systems for measuring water level NOAA Digibub (N2 Bubbler, submerged) CU optical laser system (down-looking from 12-m sump deck) Differenced data show strong sea-state dependence Up to 15 cm for SWH > 5 m. Largest sensitivity seen in Bubbler data (e.g., Parke and Gill, 1995)

12. October 27, 2008 Ocean Platforms Workshop 16 Years of Continuous GPS Monitoring

13. October 27, 2008 Ocean Platforms Workshop Periodicities in the Platform Height

14. October 27, 2008 Ocean Platforms Workshop Harvest: A Legacy of Important Contributions to Satellite Altimetry

15. October 27, 2008 Ocean Platforms Workshop Harvest: A Legacy of Important Contributions to Satellite Altimetry

16. October 27, 2008 Ocean Platforms Workshop Harvest: A Legacy of Important Contributions to Satellite Altimetry

17. October 27, 2008 Ocean Platforms Workshop Current Harvest Time Series:First SSH Calibration Results from OSTM

18. October 27, 2008 Ocean Platforms Workshop Harvest Platform GPS for Spaceborne Radiometer Calibration

19. October 27, 2008 Ocean Platforms Workshop Harvest Contributions Precise and long-term tie with global terrestrial reference frame. Coincident observations of satellites in formation flight (T/P + Jason-1, and Jason-1 + OSTM). Excellent characterization of systematic errors from long-term observation and redundant measurements. Segregation of various potential contributors to drift (e.g., Altimeter, Radiometer) Open-ocean environment tests measurement system in typical operating conditions. Important contributor to the growing network of active, dedicated calibration sites serving Jason/OSTM and oriented along the original TOPEX ground track: Corsica, Bass Strait, Gavdos, Ibiza�.

20. October 27, 2008 Ocean Platforms Workshop Other Applications: Coastal GPS Altimetry Demonstration (2001) of coastal GPS (reflections) altimetry from an offshore platform (Treuhaft et al., 2003)

21. October 27, 2008 Ocean Platforms Workshop Other Applications: GPS Buoys Demonstration of precise altimeter calibration using a GPS buoy (e.g., Born et al., 1994; Rocken et al., 1990; Kelecy et al., 1994) Other applications include marine geoid surveys, SWH, tracking subsurface acoustic probes, sea floor geodesy. Pioneering work at Harvest inspired many subsequent experiments and new approaches to pelagic GPS.

23. October 27, 2008 Ocean Platforms Workshop Acknowledgements Eric Lindstrom (NASA Physical Oceanography Program) Dave Stowers, Kevin Miller, Steve Dinardo, Steve Keihm (JPL) Chuck Fowler, Jacob Gilman, Chris Ellerhorst, Dave Miller (CCAR/CU) Dan Kubitschek (Lockheed Martin, ex. CU/JPL) UNAVCO (see poster by Andreatta et al.) Plains Exploration and Production (PXP) Divecon Dedication: Edward J. �Chris� Christensen and Yves Menard

24. October 27, 2008 Ocean Platforms Workshop Backup Material

25. October 27, 2008 Ocean Platforms Workshop Global Sea Level Record fromTopex/Poseidon and Jason-1