Global return values of marine wind speed and significant wave height are
estimated from very large aggregates of archived ensemble forecasts at +240-h
lead time. Long lead time ensures that the forecasts represent independent
draws from the model climate. Compared with ERA-Interim, a reanalysis, the
ensemble yields higher return estimates for both wind speed and significant
wave height. Confidence intervals are much tighter due to the large size of the
dataset. The period (9 yrs) is short enough to be considered stationary even
with climate change. Furthermore, the ensemble is large enough for
non-parametric 100-yr return estimates to be made from order statistics. These
direct return estimates compare well with extreme value estimates outside areas
with tropical cyclones. Like any method employing modeled fields, it is
sensitive to tail biases in the numerical model, but we find that the biases
are moderate outside areas with tropical cyclones.Comment: 28 pages, 16 figure
