1. Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations
S. A. Grodsky1
N. Reul2, G. Lagerloef3, G. Reverdin4, J. A. Carton1, B. Chapron2, Y. Quilfen2, V. N. Kudryavtsev5, and H.-Y. Kao3
1Department of Atmospheric and Oceanic Science, University of Maryland, College Park, USA
2Institut Francais pour la Recherche et l’Exploitation de la Mer (IFREMER), Plouzane, France
3Earth and Space Research, Seattle, Washington, USA
4Laboratoire d’Océanographie et de Climatologie par Expérimentation et Analyse Numérique, Institut Pierre Simon Laplace, CNRS/UPMC/IRD/MNHN, Paris, France.
5Russian State Hydrometeorological University and Nansen International Environmental & Remote Sensing Centre, St Petersburg, Russia
2012, Geophys. Res. Lett., 39, L20603, doi: /2012GL
AQUARIUS CAL/VAL meeting, GSFC, 29OCT-1NOV, 2012

2. Courtesy of N. Reul, IFREMER
SMOS-detected SSS changes in the wake of a hurricane. This is the first time such changes have been detected from space. Hurricane Igor caused the freshwater plume from the Amazon River to mix with deeper saltier waters, thereby increasing SSS.

3. How good is satellite SSS in the plume?
SSS changes observed by Aquarius and SMOS agree well suggesting that satellite sensing of SSS is a mature technique for strong signals >1 psu.
AQUARIUS is L3/v.13
SMOS is L3 from ’Centre Aval de Traitement des Données SMOS’ (CATDS)
TSG is ESA's SMOS Cal/Val effort supported by the CNES/TOSCA.

4. Argo comparison (same day, <1deg )
Tropical Buoy comparison
Argo comparison (same day, <1deg )

5. SSS before passage of hurricane Katia
AQ data are bias-corrected 1/4deg analysis of Lagerloef and Kao (pers. communication, 2012)

6. SSS difference after-before the Katia
AQUARIUS
SMOS
Solid black is 35psu contour

7. SSS difference after-before Katia
Argo profiles
Before: solid
After: --o—o--
SALT: red
TEMP: black
35psu
Before: black
After: white
SSS difference after-before Katia

8. Modification of stirring by barrier layers
S(z)
T(z)
T(z) dT dS
Zmix z
Zmix
Observed:
Price (1981)
McPhaden et al. (2009)
Sengupta et al. (2008), Wang et al. (2011), and Balaguru et al. (2012)

9. SST difference after-before the Katia
Black line is 35 psu contour

10. SSS and SST along the hurricane Katia path
Fresh pool SST is ~0.5C warmer in the hurricane wake than SST outside the pool

12. Summary
In comparison with daily in-situ near-surface salinity from tropical moorings AQUARIUS SSS is biased low by 0.1psu, STD=0.4psu.
This accuracy enables detection of SSS response to passing tropical storms in the Amazon/Orinoco plume area. Both AQ and SMOS are consistent for such ‘strong’ SSS signal.
SSS increases by ~1psu in the hurricane wake. Haline wake develops only within the plume and is associated with at least 0.5oC weaker SST cooling than outside. This difference in SST cooling is explained by additional work required to mix the BL.
Passage over freshwater plumes causes strengthening of hurricanes due to high SST and weaker cool wake due to the presence of the BL. These produce ~50% increase in intensification rate over BL regions and occur in 10-20% of tropical cyclone cases worldwide (Balaguru et al., 2012), but are more probable (68%) for the most intense (category 5) hurricanes (Ffield, 2007).