Convective rains in the Intertropical Convergence Zone produce lenses of freshened water on the ocean surface. Due to significant density differences between the freshened and saltier seawater, strong pressure gradients develop, resulting in lateral spreading of freshwater lenses in the form of gravity currents. Gravity currents inherently involve three-dimensional dynamics. As a type of organized structure, gravity currents may also interact with, and be shaped by, the ambient oceanic and atmospheric environment. Among the important environmental factors are background stratification and wind stress. Under certain conditions, a resonant interaction between a propagating freshwater lens and internal waves in the underlying halocline (the barrier layer) may develop, while interaction with the wind stress may produce an asymmetry in the freshwater lens and associated mixing. These two types of interactions working in concert may explain the series of sharp frontal interfaces observed in association with freshwater lenses during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). We conducted a series of numerical simulations using computational fluid dynamics tools. These numerical experiments were designed to elucidate the relationship between vertical and horizontal fluxes of salinity under various environmental conditions and the potential impact of these fluxes on the barrier layer and Aquarius and Soil Moisture and Ocean Salinity (SMOS) satellite image formations.

Soloviev, A.V., S. Matt, and A. Fujimura. 2015. Three-dimensional dynamics of fresh​water lenses in the ocean’s near-surface layer. Oceanography 28(1):142–149, https://doi.org/10.5670/oceanog.2015.14.

Animation of the evolution of the freshwater plume interacting with wind stress. 
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Anderson, J.E., and S.C. Riser. 2014. Near-surface variability of temperature and salinity in the near- tropical ocean: Observations from profiling floats. Journal of Geophysical Research 119:7,433–7,448, https://doi.org/10.1002/2014JC010112.
1. Asher, W.E., A.T. Jessup, R. Branch, and D. Clark. 2014. Observations of rain-induced near surface salinity anomalies. Journal of Geophysical Research: Oceans 119(8):5,483–5,500, https://doi.org/10.1002/2014JC009954.
2. Farrar, J.T., R. Schmitt, L. Rainville, W. Asher, B. Hodges, A. Jessup, F. Bingham, A. Shcherbina, W.S. Kessler, L. Centurioni, and others. 2014. Report of a Workshop in Pasadena, April 16–18, 2014. 17 pp.
3. Kuettner, J.P. 1971. Cloud bands in the earth’s atmosphere: Observations and theory. Tellus 23(4–5):404–426.
4. Lesieur, M. 2008. Turbulence in Fluids, 4th ed. Springer, Berlin, Heidelberg, 558 pp.
5. Lukas, R., and E. Lindstrom. 1991. The mixed layer of the western equatorial Pacific Ocean. Journal of Geophysical Research 96(S01):3,343–3,357, https://doi.org/10.1029/90JC01951.
6. Matt, S., A. A. Fujimura, Soloviev, and S. Rhee. 2011. Modification of turbulence air-sea interface due to the presence of surfactants and implications for gas exchange: Part II. Numerical simulations. Pp. 299–312 in Gas Transfer at Water Surfaces. Kyoto University Press.
7. Matt, S., A. Fujimura, A. Soloviev, S.H. Rhee, and R. Romeiser. 2014. Fine-scale features on the sea surface in SAR satellite imagery: Part II. Numerical modeling. Ocean Science 10:427–438, https://doi.org/10.5194/os-10-427-2014.
8. Nicoud, F., and F. Ducros. 1999. Subgrid-scale stress modelling based on the square of the velocity gradient tensor. Flow, Turbulence and Combustion 62:183–200.
9. Özgökmen, T.M., P.F. Fischer, J. Duan, and T. Iliescu. 2004. Three-dimensional turbulent bottom density currents from a high-order nonhydrostatic spectral element model. Journal of Physical Oceanography 34:2,006–2,026, https://doi.org/10.1175/1520-0485(2004)034<2006:TTBDCF>2.0.CO;2.
10. Simpson, J.E. 1987. Gravity Currents: In the Environment and the Laboratory. Ambient Stratification. Ellis Horwood Limited, NY, 186 pp.
11. Soloviev, A.V., and R. Lukas. 1997. Sharp frontal interfaces in near-surface layer of the ocean in the western equatorial Pacific warm pool. Journal of Physical Oceanography 27:999-1,017, https://doi.org/10.1175/1520-0485(1997)027<0999:SFIITN>2.0.CO;2.
12. Soloviev, A.V., and R. Lukas. 2014. The Near-Surface Layer of the Ocean: Structure, Dynamics, and Applications, 2nd ed. Springer, NY, 552 pp.
13. Soloviev, A.V., R. Lukas, and H. Matsuura. 2002. Sharp frontal interfaces in the near-surface layer of the tropical ocean. Journal of Marine Systems 37(1–3):47–68, https://doi.org/10.1016/S0924-7963(02)00195-1.
14. Stommel, H. 1993. A conjectural regulating mechanism for determining the thermohaline structure of the oceanic mixed layer. Journal of Physical Oceanography 23(1),142–148, https://doi.org/10.1175/1520-0485(1993)023<0142:ACRMFD>2.0.CO;2.
15. Strelets, M. 2001. Detached eddy simulation of massively separated flows. AIAA 2001-0879, 39th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV.
16. Vinayachandran, P.N., V.S.N. Murty, and V. Ramesh Babu. 2002. Observations of barrier layer formation in the Bay of Bengal during summer monsoon. Journal of Geophysical Research 107, https://doi.org/10.1029/2001JC000831.
17. Wijesekera, H.W, C.A. Paulsom, and A. Huyer. 1999. The effect of rainfall on the sea surface layer during a westerly wind burst in the western equatorial Pacific. Journal of Physical Oceanography 29(4):612–632, https://doi.org/10.1175/1520-0485(1999)029<0612:TEOROT>2.0.CO;2.

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