Extreme Wind Atlas by reanalysis data

WAsP Engineering needs input for site-specific extreme-wind estimates. For this we generally recommend local measurements or representative data from a not too distant meteorological stations. The WAsP Climate Analyst can help you process the raw data and WAsP Engineering can convert the winds to standard conditions (10 m above uniform flat terrain with 5 cm surface roughness length) and store the result in a regional extreme wind climate (REWC). In either case, the measurements should be of good quality and sufficient duration. The IEC 61400-1 standard suggests no less than seven years! Such data are not always available and as a substitute you might use data from the NCEP/NCAR reanalysis dataset.

Risø has developed a method based on geostrophic wind estimates using reanalysis surface-pressure data, see references below. The effect of the disjunct sampling in the reanalysis data is compensated by a 13% correction and the results are stored in REWC format. The method should be considered preliminary and, due to the relatively low resolution in the reanalysis computations, the extreme wind estimates are not reliable in mountain areas, e.g. the US Rocky Mountains, or regions with tropical cyclones. We are hoping to refine the method by mesoscale modelling of individual storms using reanalysis data as boundary conditions only.

Meanwhile you can download zip files with preliminary REWC files for Europe and USA

• Preliminary extreme wind atlas from Europe based on data from 1979 to 2004
• Preliminary extreme wind atlas from USA based on data from 1979 to 2005  (a format error was corrected 11/1-2007)

The file names indicates the latitude and longitude of the reanalysis data.

References

1. Xiaoli Guo Larsén, Jakob Mann and Hans E. Jøgensen. Extreme winds and the connection to reanalysis data. Proceedings of the one-day conference on Extreme Winds and Developments in Modelling of Wind Storms, Cranfield University, 15th September 2004.
2. Jakob Mann, Xiaoli Guo Larsen And Hans E. Jørgensen. Regional Extreme Wind Climate and Local winds using WAsP Engineering. Proceedings of the one-day conference on Extreme Winds and Developments in Modelling of Wind Storms, Cranfield University, 15th September 2004.

Extreme wind data derived from NCEP/NCAR reanalysis data. The large number of annual observations improves the uncertainty of the Gumbel fit.

Predicted omnidirectional fifty-year extreme reduced wind over Spain, i.e. 10m above uniform flat terrain with 5cm surface roughness.

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