Abstract's details
Impact of waves on storm surges in the North Sea: model evaluation against altimeter
CoAuthors
Event: 2018 Ocean Surface Topography Science Team Meeting
Session: Tides, internal tides and high-frequency processes
Presentation type: Type Oral
Contribution: PDF file
Abstract:
Impact of waves on storm surges in the North Sea: model evaluation against altimeter
Lucia Pineau-Guillou, Marie-Noëlle Bouin, Fabrice Ardhuin and Florent Lyard
Satellite altimeters measure the Sea Surface Height (SSH), which includes the Mean Sea Surface Height (MSSH), the Sea Level Anomaly (SLA), the tides and the sea level variations of atmospheric origin (wind and atmospheric pressure). SSH are routinely corrected from high-frequency signals of atmospheric origin like surges. This de-aliased correction is generally computed using a global ocean model and removed from altimeter measurements to obtain Sea Level Anomaly (SLA). The accuracy of modeled storm surges is then essential, as it impacts directly the accuracy of SLA products.
In ocean models, wind stress is parameterized using bulk formulae, that express it as a function of the wind speed and of a drag coefficient. Various wind stress parameterizations can modify the resulting storm surges amplitude by up to 20% (Mastenbroek et al., 1993; Muller et al., 2014). Most formulations depend only on the wind speed - e.g. Hellerman and Rosenstein (1983) in TUGO ocean model (Lyard et al., 2006), whereas others take into account the wave effect on the drag coefficient through a larger roughness length for a given wind-speed - e.g. Janssen (1991) in ECMWF (European Centre for Medium-Range Weather Forecasts) coupled wave-atmosphere model.
Here, we use the TUGO global ocean model and various wind stress bulk formulae to investigate the possible effect of the waves on the storm surges signal. For different storm case studies in the North Sea, we compare simulated storm surges with in situ tide gauges and altimeter measurements from JASON-2. Two wind stress parameterizations are tested in the ocean model: the first one is wind-dependent only, the second is wind- and wave-dependent.
Hellerman, S. and Rosenstein, M. (1983). Normal monthly wind stress over the world ocean with error estimates. J. Phys. Oceanogr., 13(7):1093–1104.
Janssen, P. A. E. M. (1991). Quasi-linear theory of wind wave generation applied to wave forecasting. J. Phys. Oceanogr., 21:1631–1642. See comments by D. Chalikov, J. Phys. Oceanogr. 1993, vol. 23 pp. 1597–1600.
Lyard, F., Lefevre, F., Letellier, T., and Francis, O. (2006). Modelling the global ocean tides: modern insights from FES2004. Ocean Dynamics, 56:394–415.
Mastenbroek, C., Burgers, G., and Janssen, P. A. E. M. (1993). The dynamical coupling of a wave model and a storm surge model through the atmospheric boundary layer. J. Phys. Oceanogr., 23:1856–1867.
Muller, H., Pineau-Guillou, L., Idier, D. and Ardhuin, F. (2014). Atmospheric storm surge modeling methodology along the French (Atlantic and English Channel) coast. Ocean Dyn. 64: 1671–1692.
Lucia Pineau-Guillou, Marie-Noëlle Bouin, Fabrice Ardhuin and Florent Lyard
Satellite altimeters measure the Sea Surface Height (SSH), which includes the Mean Sea Surface Height (MSSH), the Sea Level Anomaly (SLA), the tides and the sea level variations of atmospheric origin (wind and atmospheric pressure). SSH are routinely corrected from high-frequency signals of atmospheric origin like surges. This de-aliased correction is generally computed using a global ocean model and removed from altimeter measurements to obtain Sea Level Anomaly (SLA). The accuracy of modeled storm surges is then essential, as it impacts directly the accuracy of SLA products.
In ocean models, wind stress is parameterized using bulk formulae, that express it as a function of the wind speed and of a drag coefficient. Various wind stress parameterizations can modify the resulting storm surges amplitude by up to 20% (Mastenbroek et al., 1993; Muller et al., 2014). Most formulations depend only on the wind speed - e.g. Hellerman and Rosenstein (1983) in TUGO ocean model (Lyard et al., 2006), whereas others take into account the wave effect on the drag coefficient through a larger roughness length for a given wind-speed - e.g. Janssen (1991) in ECMWF (European Centre for Medium-Range Weather Forecasts) coupled wave-atmosphere model.
Here, we use the TUGO global ocean model and various wind stress bulk formulae to investigate the possible effect of the waves on the storm surges signal. For different storm case studies in the North Sea, we compare simulated storm surges with in situ tide gauges and altimeter measurements from JASON-2. Two wind stress parameterizations are tested in the ocean model: the first one is wind-dependent only, the second is wind- and wave-dependent.
Hellerman, S. and Rosenstein, M. (1983). Normal monthly wind stress over the world ocean with error estimates. J. Phys. Oceanogr., 13(7):1093–1104.
Janssen, P. A. E. M. (1991). Quasi-linear theory of wind wave generation applied to wave forecasting. J. Phys. Oceanogr., 21:1631–1642. See comments by D. Chalikov, J. Phys. Oceanogr. 1993, vol. 23 pp. 1597–1600.
Lyard, F., Lefevre, F., Letellier, T., and Francis, O. (2006). Modelling the global ocean tides: modern insights from FES2004. Ocean Dynamics, 56:394–415.
Mastenbroek, C., Burgers, G., and Janssen, P. A. E. M. (1993). The dynamical coupling of a wave model and a storm surge model through the atmospheric boundary layer. J. Phys. Oceanogr., 23:1856–1867.
Muller, H., Pineau-Guillou, L., Idier, D. and Ardhuin, F. (2014). Atmospheric storm surge modeling methodology along the French (Atlantic and English Channel) coast. Ocean Dyn. 64: 1671–1692.