Estimating Extreme Waves in Brazil Using Regional Frequency Analysis

Regional Frequency Analysis (RFA) based on L-moments is used to calculate spatial extreme return values of significant wave height. The RFA consists of using data from different sites with similar statistical characterisation to better estimate quantile functions, which can be used for regional or site-specific analyses. This technique is applied to a selected area in the South Atlantic Ocean (Brazil) using a group of wave hindcasts produced by a simulation with WAVEWATCH III model. The statistical approach of RFA is divided into four steps: (1) First inspection of the data; (2) Regionalization and definitions of statistically homogeneous sub-regions; (3) choice of Probabilistic Distribution and test of hypothesis; (4) Calculation of L-moments and final regional quantile function. The results of RFA are reliable extreme return values at each grid point with very low variance of the distribution parameters estimators and narrow confidence intervals. Considering the return period of 100 years, the significant wave heights vary from 5.5 to 11.2 meters within the considered domain in southern and southeastern Brazil.