SPURS Results Abstracts


SPURS Results

Salinity Processes in the Upper Ocean Regional Study (SPURS)
Contact author: Eric Lindstrom
Eric Lindstrom, NASA Headquarters

Validation of Aquarius Sea Surface Salinity Data with In Situ Measurements from the SPURS Field Experiment
Contact author: Yi Chao, <ychao@remotesensingsolutions.com>
All Authors:
Yi Chao, Remote Sensing Solutions
Hongchun Zhang, UCLA
Luca Centurioni, UCSD/SIO
Tom Farrar, WHOI
Dave Fratantoni, 5Horizon Marine
Ben Hodges, WHOI

In situ measurements collected from the SPURS (Salinity Processes in the Upper Ocean Regional Study) field experiment during September 2012 – October 2013 are used to quantify the mismatches between the sea surface salinity (SSS) as retrieved from the Aquarius L-band radiometer and Argo profiling floats. What is the SSS variability within the 7-day Aquarius satellite orbit repeat cycle? What is the SSS variability within the three Aquarius footprints? What is the vertical stratification between salinity measured by the Aquarius L-band radiometer at about 1 cm and measurements by in situ sensors/platforms at various depths from 1 cm to 10 m? Using the multiple independent in situ measurements, the accuracy for the Aquarius retrieved SSS in the SPURS region is assessed, and compared to the accuracy assessed by the standard Argo profiling float. Using the four independent data types, we can select any three data types to perform triple-point analysis to derive the weekly Aquarius error in the range of 0.13 to 0.14 psu, which is already smaller the allocated monthly error of 0.16 psu.

The North Atlantic Subtropical Surface Salinity Maximum as Observed by Aquarius
Contact author: Frederick Bingham, <frederick.bingham@gmail.com>
All Authors:
Frederick Bingham, University of North Carolina Wilmington
Julius Busecke, Lamont Doherty Earth Observatory of Columbia University
Claudia Giulivi, Lamont Doherty Earth Observatory of Columbia University
Arnold Gordon, Lamont Doherty Earth Observatory of Columbia University
Zhijin Li, Jet Propulsion Laboratory, California Institute of Technology

Aquarius satellite derived sea surface salinity (SSS) data from August 2011 through September 2013 reveals significant seasonal migration and freshening of the subtropical surface salinity maximum (SSS-max) area in the North Atlantic, in good agreement with in situ observations, including those obtained as part of the SPURS (Salinity Processes in the Upper Ocean Regional Study) field experiment in 2012-2013. The SSS-max fluctuated in surface area – as defined by the 37.4 surface isohaline – during the course of the Aquarius time series by about 67%. The SSS-max has a surprisingly large amount of non-seasonal variability, including a general decrease in salinity throughout the eastern subtropical North Atlantic between 2011-2012 and 2012-2013 of about 0.1-0.2. The documented seasonal variability is weakest in the maximum salinity area and increases towards the north and south respectively. This is consistent with the important role played by Ekman transport and regional excess of evaporation over precipitation in the formation of the SSS-max.

Regional rainfall measurements using Passive Aquatic Listener during SPURS field campaign
Contact author: Jie Yang, <jieyang@apl.washington.edu>
All Authors:
Jie Yang, University of Washington Applied Physics Laboratory
Stephen Riser, Dept. Of Oceanography, University of Washington
Jeffrey Nystuen, University of Washington Applied Physics Laboratory
William Asher, University of Washington Applied Physics Laboratory
Andrew Jessup, University of Washington Applied Physics Laboratory

Knowledge of the intensity and spatial-temporal distribution of rainfall over the ocean is critical in understanding the global hydrological cycle. However, rain has proven to be difficult to measure over the ocean due to problems associated with deploying rain sensors from moving platforms combined with the spatial and temporal variability of rainfall itself. Underwater acoustical rain gauges avoid the issues of surface rain sensors by using the loud and distinctive underwater sound generated by raindrops on the ocean surface to detect and quantify rainfall. Here, the physics, operation, and results from an instrument that uses underwater ambient sound to measure rainfall rate and wind speed are presented. Passive Aquatic Listener (PAL) instruments were mounted on a buoy deployed at Ocean Station P and on sixteen Argo profilers that were deployed as part of the NASA-sponsored Salinity Processes in the Upper ocean Regional Studies (SPURS) field experiment in the North Atlantic Ocean. The PALs provide near-continuous measurements of rain rate and wind speed over the two-year period over the SPURS study region defined by the Argo profilers. Comparisons of the PAL data with rain and wind measured by other techniques including direct in situ observations and satellite measurements show good agreement for both rain rate and wind speed.