1. 1 Satellite & In Situ Salinity (SISS) Working Group: Current status and future plans Co-Chairs: J. Boutin (LOCEAN/CNRS), Yi Chao (RSSI) Web page: siss.locean-ipsl.upmc.fr Next meeting: EGU 2015 meeting (if you’d like to attend, thanks for contacting us: jb@locean-ipsl.upmc.fr, ychao001@gmail.com)

2. 2 Satellite & In Situ Salinity (SISS) Working Group Established at the SMOS-Aquarius science workshop during 15-17 April 2013 in Brest/France Co-chairs: – Jacqueline Boutin (LOCEAN/CNRS; SMOS) – Yi Chao (RSSI; Aquarius) Goal: – To improve our understanding of the link between L- band satellite (SMOS and Aquarius) remotely sensed salinity (for approximately the top 1 cm of the sea surface) and in situ measured salinity (routinely measured at a few meters depths by in situ sensors) and to develop practical methodologies for relating satellite salinity to other estimates of sea surface salinity.

3. 3 Questions that this WG should particularly address are: 1.What is the salinity stratification in the first 10m below the sea surface and its relation with the atmospheric forcing including wind and rain? Under what circumstances (particular atmospheric conditions and/or geographical regions) are the new satellite SSS able to provide a new reliable information on SSS within the first cm complementary to existing deeper in situ information for studying air-sea exchange processes? In case of a rain event, what is the magnitude of and could we correct for other effects than salinity affecting L-band radiometric measurements (roughness, atmosphere)? 2.What is the magnitude of SSS variability within satellite footprint (SMOS (40 km) and Aquarius (50-150 km)); how can we take it into account in in-situ and satellite SSS comparisons? 3.Which kind of experimental/numerical experiences could be envisaged for studying processes at play & answering above questions? Satellite & In Situ Salinity (SISS) Working Group

4. 4 Satellite & In Situ Salinity (SISS) Working Group Activities Web site – http://siss.locean-ipsl.upmc.fr/ Mailing list – 83 members Meetings (informal) – AGU Ocean Sciences Meeting in Feb 2014 – EGU meeting in April 2014 – AGU Fall Meeting in December 2014 – Next: EGU 2015

5. 5 Satellite & In Situ Salinity (SISS) Working Group Tasks 1 st Task (established at AGU OS meeting in Feb 2014) – To produce a schematic diagram of the near surface salinity (12 members) 2 nd Task (established at AGU Fall meeting in Dec 2014) – To produce a white paper to be submitted to BAMS about SISS issues (task team : 21 members)

6. 6 SISS meeting during AGU Fall meeting: ~30 participants Short Presentations: Large scale/mesoscale/rain Gary Lagerloef Open issues in Aquarius SACD SSS Lisan Yu The Salinity Regimes in the Tropical Ocean- Implications for Satellite – In situ Comparisons Fred Bingham Comparison of Distributional Statistics of Argo and Aquarius Sea Surface Salinity Measurements Christophe Maes Small scale features detected by ship TSG Peter Hacker A high-resolution Aquarius OI SSS L4 analysis: 3-year, near-global, weekly, 0.5 degree grid James Reagan "Comparison analysis between Aquarius sea surface salinity and World Ocean Database in situ analyzed sea surface salinity" Thomas Meissner"Rain Freshening observed by Aquarius" Wenquing Tang rain stratification effect revealed in comparison of Aquarius and drifters measurements Kyla Druschka 1D modelling of fresh water lenses Alexander Soloviev"3D dynamics of freshwater lenses in the near-surface ;layer of the ocean" Tony Song Modeling satellite-observed skin-layer salinity with an extended surface-salinity layer Presentations available on siss.locean-ipsl.upmc.fr

7. 7 Figure. Latitude-time distributions of the zonally averaged differences between the weekly SSS maps and the corresponding Argo buoy data for three SSS analyses: (a) standard Level-3 product without bias correction; (b) standard Level-3 SSS product with SST-dependent bias correction; and (c) OI SSS analysis of this paper. Units are psu. Error statistics were computed by comparing Argo buoy observations for a given week with SSS values at the same locations obtained by interpolation of the corresponding SSS maps. The zonally averaged biases were computed by averaging these statistics over 5-degree latitude bands. Latitude-time distributions of zonally averaged differences between weekly AQUARIUS SSS maps and Argo data v3 standard v3 SST bias cor. OI SSS Menilchenko et al. 2014 Note reduced annual cycle bias in OI SSS product.

8. 8 ThermoSalinograph data CARS09 clim. Maes et al., JGR 2013 Noumea---> Solomon MATISSE CGM SBE21 TSG data for 2010 >> Delayed mode : 5-min processing + in situ data (water samples & Argo data) to adjust the SSS Dec-Jan Apr-Jun Aug-Oct

9. 9

10. 10 After rescaling rain rate to take into account the mooving ship

11. U 10 = 8 m/s 3D Dynamics of Freshwater Plumes Produced by Convective Rains Alexander Soloviev a,b, Cayla Dean a, Silvia Matt a,c, Atsushi Fujimura b Conclusions: Convective rains within ITCZ produce localized freshwater lenses, which have tendency to spread horizontally Lenses resemble gravity currents and can interact with wind stress [and ambient stratification] 3D processes are noticeably involved (unless lens has achieved a compensated state) Model results suggest that freshwater lenses can significantly evolve on time scale O(1 hr)

12. Proposed Title: Satellite & In Situ Surface Salinity: Stratification and Sub-footprint variability 1.Introduction Objectives of the paper Summary of existing knowledge What we know What we don’t know & what needs to be done Description of ‘normal’ conditions 2.Vertical stratification & sub-footprint variations 2.1Rain impact 2.2Fresh-water plumes 2.3Mesoscale/Submesoscale dynamics (e.g., fronts, eddies, filaments) 2.4Evaporation 3.Summary, Recommendations White paper Writing teams

13. Salinity Well Mixed Salinity Depth Stratified with Rain Depth Salinity Depth Stratified with Evaporation Near-Surface Salinity Schematic Diagram for L-band Radiometer Following AGU SF meeting Rain-induced fresh layer Evaporation- induced salty layer Satellite L-band radiometric salinity at depth range from 1 to 10 cm Figure 1 of BAMS paper...

14. 14 SISS WG Future Plan and Activities Proposal for a BAMS paper has been submitted last week Exchanges ongoing with potential Leaders/co- leaders of each chapter First drafts to be discussed at EGU 2015 Submission foreseen in Summer 2015

15. 15 Much more fresh SMOS SSS cells than rain cells: why??? history of rain? Advection of fresh cells? RFIs??? Possible actions in 2015-2016: -Participation to SPURS2 (lead: US; preparation meeting March 2015) experiment => sample fresh cells variability (horizontal/vertical) in Pacific ITCZ. French participation: deployment of drifters - ESA STSE SMOS+Rainfall (Statement of work: produce a rain product) Relate rainrate and SMOS SSS fresh cells - Better understand surface processes (role of wind speed (mixing), advection of rain cells and of freshwater lenses, SST) - Estimate a rain rate simultaneous to SMOS (=> atm. Corr. In L2OS (~20%)) Future of SMOS SSS-Rain studies X SPURS2

16. 16 Extra slides

17. Rain Freshening: Global About 80-90% of the observed effect is due to rain freshening. The rest is due to atmosphere + surface splashing. Low winds: freshening is about - 0.13 to - 0.15 psu/(mm/h) About 80-90% of the observed effect is due to rain freshening. The rest is due to atmosphere + surface splashing. Low winds: freshening is about - 0.13 to - 0.15 psu/(mm/h) Low winds Surface layer stratified High winds Surface layer mixed AQUARIUS (150km resolution, S 1cm ), ~0.12pss/mm/hr (Meissner et al. 2014) SMOS (40km resolution, S 1cm ), > ~0.14 pss/mm/hr (Boutin et al. 2014) NB: Santos-Garcia et al., 2014 : 0.36-0.2 using AQUARIUS & CMORPH: an effect of rain product?

18. 18 One example of the impact of eddies stirring /submesoscale structures TSG data FSLE data WPWP waters subtropical waters

19. 19 Boutin et al., 7th Aquarius/SAC-D Science Meeting, 11-13 April 2012 Ship SMOS 10d-100km ARGO OI ARGO OI much smoother than Ship SSS: monthly & ~1 ARGO meas./10days, 2° SMOS (40km resolution) better sees small scale variability, but still some deficiencies (distance to coast?, RFI, islands…) On average: SSS ARGO_OI -SSS TSG = 0.2 (0.23) SSS SMOS -SSS TSG = 0.0 (0.37) SSS latitudinal profiles – Ship-ARGO OI- SMOS

20. Salinity Well Mixed Salinity Depth Stratified with Rain Depth Salinity Depth Stratified with Evaporation Near-Surface Salinity Schematic Diagram for L-band Radiometer As discussed before AGU SF meeting Rain-induced fresh layer Evaporation- induced salty layer Satellite L-band radiometric salinity at depth range from 1 to 10 cm Salinity measured by in situ sensors/platforms at depth (e.g., S 5m )