For the assessment of the safety of the Dutch flood defences extreme open-water winds need
to be computed. There are, however, no sufficiently long and reliable in-situ data available.
On the other hand, there is a rich dataset of decades of measurements at certain coastal and
relatively close by inland stations. A commonly used two-layer model for neutral atmospheres
was thought to provide reasonably accurate open-water winds from the available data, given
that the model assumptions seemed plausible for the extreme winds of interest. However, the
model results were deemed inaccurate and not usable. Given that this was unexpected, many
of the model assumptions were analysed and, with the gained further insight, their validity and
contribution to the invalidity of the deemed simple model approach assessed. Our conclusion
is that the quality of the model results is significantly affected by at least two aspects: the
assumption of neutral stability in the model, and -equally important- the assumption of
independence between the surface roughness and the wind speed.
S Caires, H de Waal, J Groeneweg, G Groen, N Wever, C Geerse, M Bottema. Assessing the uncertainties of using land-based wind observations for determining extreme open-water winds
Status: accepted, Journal: J. Wind Eng. and Ind. Aerodyn., Year: 2012