1. Salinity Processes in the Upper Ocean Regional Study Update on SPURS-2 (‘Fresh SPURS’) and SPURS-1 synthesis

2. Update from Dr. Eric Lindstrom SPURS main question: What is controlling the upper ocean salinity? Will be addressed with interagency and international collaboration using measurements from satellites, ships, drifters, floats, gliders, AUVs and modeling. Understanding salinity processes that lead to the maintenance of the observed salinity structures Also understand sub-pixel variability and vertical stratification and their effects on Aquarius retrievals

3. Update from Dr. Eric Lindstrom SPURS-2 is bookend to SPURS-1 What are the physical processes responsible for the location, magnitude and maintenance of the low surface salinity region in the Gulf of Panama? How will the ocean respond to changes in thermal and freshwater forcing associated with a changing climate? What is the nature of the cascade of salinity variance from the largest (climate) scales down to dissipation scales of a few millimeters?

4. Update from Dr. Eric Lindstrom SPURS-2 will be centered around 125°W, 10°N Lagrangian assets: Surface salinity drifters, the mixed-layer float (MLF), Argo floats, as well as Seagliders and Wave gliders Eulerian assets: central mooring, Seagliders and Wave Gliders. Core PIs: T. Farrar (Moorings), J. Sprintall (CTD), J. Schanze (Sea Snake), W. Asher (SSP/TSG), C.-A. Clayson (Met), L. Centurioni (Drifters), B. Hodges (Wave Gliders), A. Shcherbina (MLF), L. Rainville (Seagliders), S. Riser (Argo), F. Bingham (Data Management), and Z. Li (Modeling).

5. Update from Dr. Eric Lindstrom SPURS-2 will be centered around 125°W, 10°N Three cruises of approximately 30 days each Nominally starting at August 1, 2016, February 1, 2017, and September 1, 2017 using a Global Class Research Vessel. Alternative: SS Lady Amber

6. Update from Dr. Yi Chao Sub-pixel variability observed in the SPURS-1 region Consequences for Aquarius retrievals and error budgets for all data sources Mission requirement for 0.2 psu accuracy in monthly maps may be an ill-posed problem Do we have a ground truth? (no, not really) Differences between surface and ‘bulk’ salinity Argo is not a gold standard

7. Update from Dr. Yi Chao Triple point analyses using all possible combinations show 0.13-0.14 psu RMSE for Aquarius (better than error allocation!) Sub-footprint variability was estimated to contribute between 0.08- 0.1 psu RMSE (from Beam 1 to Beam 3) Vertical stratification effects are estimated to contribute 0.076 psu RMSE

8. Update from Dr. Fred Bingham Formation of subtropical underwater in the SPURS-1 region Tracking SSS features using 8 Aquarius tracks Northward propagation of salinity features originating in ITCZ Strong positive E-P leads to salinification SSS maximum (SSSM) location relatively constant Stronger inter-annual than inter-seasonal changes

9. Update from Dr. Fred Bingham Strong precipitation identified in late 2012 and early 2013 from ERA- Interim E-P Explains differences seen between 2012 and 2013 cruises. Proposed negative feedback: High SSS in SSSM -> higher salinity subducted subtropical underwater (STUW) -> greater stratification between surface and STUW -> decreased detrainment of freshwater from the surface as it flows poleward -> decreased surface salinity in SSSM

10. Update from Dr. Jie Yang Passive Acoustic Listener (PAL) calibration using 6-year Ocean Station PAPA data Excellent agreement in both wind speed measurements and rain rates In SPURS region, PAL compares favorably with the central mooring comparison of rain accumulation between PAL and 3B42 (TRMM) between February 2013 and January 2014 Overall, a good agreement is found between TRMM and PAL

11. Update from Dr. Jie Yang The seasonal and inter-annual variability in the SPURS region from PAL found much more rain in 2012 and early 2013 This explains fresher SSSM in SPURS region during early 2013 cruise PAL has been established to provide reliable estimates based on PAPA data Can be used to study the spatial variability and intermittency of rainfall and provide regional maps of the wind field