Extreme Wind-Wave modeling and statistics in the Atlantic Ocean

Abstract

Extreme surface winds and ocean waves pose a major threat to marine and coastal safety. Their induced risks depend on the location and time, being liable to important intensification due to climate changes. The extreme wind and wave climate in the Atlantic Ocean will be investigated and future prognostics as well as long-term extreme quantiles will be estimated, using a regional approach. It involves a new methodology joining the stochastic extreme value theory with numerical simulations of the climate. A calibration of wind-wave reanalysis using satellite and buoy data focused on higher percentiles will generate the database for this study, of wind speed and significant wave height. Since the surface winds control the wave spectra growth, a deep investigation of the storm tracks, patterns, associated statistics, and possible modifications due to climate changes will be conducted. A statistical regionalization will define strategic locations with higher vulnerability, where the statistical modeling must be performed in more detail and better resolution. The study domain is the Atlantic Ocean, starting from large-scale analysis and moving to regional analyses involving local aspects of the extreme wind and wave climates. The discussions involving the South Atlantic Ocean will be carried out by the research group of the University of Sao Paulo (USP), while the North Atlantic Ocean by the University of Lisbon (UL). The proposal is divided in seven tasks: (1) Assessment of three waves and winds reanalysis in the Atlantic Ocean using scatterometer, altimeter and buoy data; (2) Calibration of reanalysis focused on the improvement the extreme quantiles; (3) Storm tracking applied to the calibrated reanalysis; (4) Application of Regional Frequency Analysis (RFA) to define statistically homogeneous regions, selecting those with severe wind and wave climate presenting higher vulnerability; (5) Full description and investigation of the wind and wave climate inside each region; (6) Evaluation of the CMIP5 Climate Models and selection of the models that best represent winds and waves characteristics within strategic regions; (7) Long-term extreme analysis using L-moments and different probability distribution functions, calculating extreme values (extrapolated quantiles) for return periods up to 100 years. We expect the following results: three calibrated reanalysis for the Atlantic Ocean suitable for metocean design criteria studies; definition of strategic regions with higher vulnerability followed by a complete characterization of its wind and wave climates as well as cyclonic activities; evaluation of storm tracks associated with extreme events, looking at possible climate change impacts on the tracks and intensities; and maps of reliable extreme values with return periods up to 100 years - a new Atlas of extreme events in the Atlantic Ocean. (AU)