Abstract's details
The Harvest Experiment: New Results From the Platform and Moored GPS Buoys
CoAuthors
Event: 2019 Ocean Surface Topography Science Team Meeting
Session: Regional and Global CAL/VAL for Assembling a Climate Data Record
Presentation type: Type Oral
Contribution: PDF file
Abstract:
We describe the latest satellite radar altimeter calibration/validation (CALVAL) results from the Harvest offshore platform, located 10 km off the coast of central California near Point Conception. The platform has hosted a dedicated CALVAL facility for 27 years, dating to the launch of TOPEX/POSEIDON (T/P) in August 1992. The T/P repeat ground track was designed to take the satellite directly over Harvest every ten days, enabling the development of a continuous calibration record based on direct, overhead passes of the platform. The crucial role of T/P in developing a climate-quality record of sea level and ocean circulation has been inherited by the Jason series of reference missions, which have traced out the same 10-d repeat ground track passing through the platform.
We have conducted a number of campaigns to fortify the in-situ observing systems in the Southern California bight, with Harvest remaining as the focal point. These campaigns have two important purposes: 1) to address risk that the platform, which is no longer actively drilling, may be permanently shut down and dismantled; and 2) to prepare for the increasing demands of future altimeter missions, especially SWOT and Sentinel-6, for denser in-situ monitoring. In this presentation, we describe the latest results from both the Harvest platform and regional campaigns, and discuss prospects for future observing systems.
Based on data collected at Harvest during 93 overflights of the latest (Jason-3) mission, we estimate the sea-surface height (SSH) bias is –14 mm. The SSH bias estimates for legacy (T/P and Jason-1/2) systems are in the range of ±15 mm, and none are statistically distinguishable from zero when systematic errors sources—such as the platform geocentric position error—are properly considered.
In August, 2018, two precision GPS buoys were moored in the vicinity of Harvest to assess the potential of such systems to replace CALVAL functions of the platform. Over 110 days of continuous high rate (1-Hz) GPS data were successfully collected by both buoys systems. Significant wave heights in excess of 6 m were experienced during this tandem buoy campaign, enabling a robust evaluation of the GPS buoy performance over a wide range of open-ocean conditions. We characterize the accuracies of both relative and absolute SSH from the buoys, and discuss the prospects for using GPS buoys in place of Harvest and to support the validation of SWOT measurements. Finally, we report on the status of regional tide gauge campaigns in the California bight, focusing on the emerging time series from the lidar system on Santa Catalina Island.
We have conducted a number of campaigns to fortify the in-situ observing systems in the Southern California bight, with Harvest remaining as the focal point. These campaigns have two important purposes: 1) to address risk that the platform, which is no longer actively drilling, may be permanently shut down and dismantled; and 2) to prepare for the increasing demands of future altimeter missions, especially SWOT and Sentinel-6, for denser in-situ monitoring. In this presentation, we describe the latest results from both the Harvest platform and regional campaigns, and discuss prospects for future observing systems.
Based on data collected at Harvest during 93 overflights of the latest (Jason-3) mission, we estimate the sea-surface height (SSH) bias is –14 mm. The SSH bias estimates for legacy (T/P and Jason-1/2) systems are in the range of ±15 mm, and none are statistically distinguishable from zero when systematic errors sources—such as the platform geocentric position error—are properly considered.
In August, 2018, two precision GPS buoys were moored in the vicinity of Harvest to assess the potential of such systems to replace CALVAL functions of the platform. Over 110 days of continuous high rate (1-Hz) GPS data were successfully collected by both buoys systems. Significant wave heights in excess of 6 m were experienced during this tandem buoy campaign, enabling a robust evaluation of the GPS buoy performance over a wide range of open-ocean conditions. We characterize the accuracies of both relative and absolute SSH from the buoys, and discuss the prospects for using GPS buoys in place of Harvest and to support the validation of SWOT measurements. Finally, we report on the status of regional tide gauge campaigns in the California bight, focusing on the emerging time series from the lidar system on Santa Catalina Island.