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Saildrone (https://www.saildrone.com) is a state-of-the-art, wind and solar powered unmanned surface vehicle (USV) capable of long distance deployments lasting up to 12 months. The drone is autonomous in that it may be guided remotely from land while being completely wind driven. This novel sampling platform is equipped with a suite of instruments and sensors providing high quality, georeferenced, near real-time, multi-parameter surface ocean and atmospheric observations while transiting at typical speeds of 3-5 knots. Instruments are customizable depending on the mission, but typically include anemometer, barometer, thermosalinograph, CTD, IR pyrometer, fluorometer, and CO2/dissolved oxygen sensors. Saildrones have additionally been deployed with Acoustic Doppler Current Profilers (ADCP), passive acoustic sensors and echo sounders to measure along-track 3D current velocities and biological acoustic backscatter. Saildrone adopts a service model approach to the design and implementation of missions and the delivery of data products to customers. Current deployments include the Tropical and North Pacific, with a focus on future deployments in the Arctic. Data from Saildrone are providing information being used to support NASA satellite cal/val and ocean science studies, including the improvement of salinity and SST retrievals at high latitudes and closer to the coast.
Figure 1: The Saildrone platform and its characteristics (image credit: Saildrone Inc.)
The Saildrone Baja campaign was a 60-day cruise from San Francisco Bay, down along the US/Mexico coast to Guadalupe Island and back again over the period 11 April 2018 to 11 June 2018. Repeat surveys were taken around NDBC moored buoys, and during the final week of the cruise a targeted front was sampled. The cruise track was selected to optimize both the science and validation objectives included in these projects. Scientific objectives included studies of upwelling and frontal region dynamics, air-sea interactions, and diurnal warming effects, while its validation objectives included establishing the utility of data from the Saildrone platform for assessment of satellite data accuracy and model assimilation. Validation efforts focus on the evaluation of Saildrone instrument performance relative also to satellite observations in a coastal upwelling region. During the Baja campaign, the single deployed Saildrone was equipped with a suite of instruments that included a CTD, IR pyrometer, fluorometer, dissolved oxygen sensor, anemometer, barometer. Additionally, four temperature data loggers were positioned vertically along the hull to provide further information on thermal variability near the ocean surface. The resulting Saildrone Baja dataset (DOI: 10.5067/SDRON-SURF0) available from the PODAAC is comprised of one data file with the Saildrone platform telemetry and near-surface observational data (air temperature, sea surface skin and bulk temperatures, salinity, oxygen and chlorophyll-a concentrations, barometric pressure, wind speed and direction) for the entire cruise at 1 minute temporal resolution. A second file contains the ADCP current vector data that is depth-resolved to 100m at 2m intervals and binned temporally at 5 minute resolution. All Saildrone data files archived at the PODAAC are in netCDF format and CF/ACDD compliant consistent with the NOAA/NCEI specification.
Sponsor Acknowledgement: Funding support for the Saildrone Baja campaign is from The Schmidt Family Foundation, Saildrone, Inc., and NASA's Physical Oceanography Program (grant number 80NSSC18K0837).
Figure 1: Baja Saildrone deployment and cruise track in relation to SST imagery
Figure 2: Animation showing the dynamic evolution of the Saildrone cruise track measurements over the course of the Baja field campaign (April 11 to June 11, 2018) relative to satellite sea surface salinity and temperature fields. The top-left panel shows the Saildrone sea water salinity data overlaid on sea surface salinity from the SMAP RSS Level 3 V3 70KM 8day running mean product. The top-right panel shows the Saildrone sea surface temperature data overlaid on mapped sea surface temperature data from GHRSST Level 4 MUR V4.1. The bottom-left panel plots the Saildrone sea water salinity data (black line) relative to collocated SMAP RSS sea surface salinity data (green line). The red line is the Saildrone Chlorophyll concentration in mg/l. The bottom-right plot represents Saildrone SST (black line) and collocated MUR SST data (green). The red line is the Saildrone sea water bulk temperature measurement.
Figure 3: Comparison of Saildrone and collocated satellite sea surface temperature observations over the Baja campaign cruise track. Images were kindly provided by the Ensenada Center for Scientific Research and Higher Education, Baja California, Mexico (CICESE).
NASA is focusing on improving satellite derived sea surface temperate (SST) and sea surface salinity (SSS) in the Arctic (two essential climate variables). SSTs efforts are funded through the National Ocean Partnership Program, a collaboration between the NAVY, NOAA, and NASA. Arctic Saildrone data sets that in the future will be archived and available via the PODAAC will provide critical validation of these two parameters in an important part of the World’s Oceans.