  An offshore wind turbine needs to withstand the environmental loads, which
can be expected during its life time. Consequently, designers must define loads
based on extreme environmental conditions to verify structural integrity. The
environmental contour method is an approach to systematically derive these
extreme environmental design conditions. The method needs a probability density
function as its input. Here we propose the use of constant bandwidth kernel
density estimation to derive the joint probability density function of
significant wave height and wind speed. We compare kernel density estimation
with the currently recommended conditional modeling approach. In comparison,
kernel density estimation seems better suited to describe the statistics of
environmental conditions of simultaneously high significant wave height and
wind speed. Consequently, an environmental contour based on kernel density
estimation does include these environmental conditions while an environmental
contour based on the conditional modeling approach does not. Since these
environmental conditions often lead to the highest structural responses, it is
especially important that the used method outputs these conditions as design
requirements.
