European windstorms · Observatoire des phénomènes naturels

A storm is measured by the excess of wind over what is usual where it blows. For each day, the severity index (Leckebusch et al., 2008) sums, over Europe and the north-east Atlantic, the cube of the excess of the daily maximum gust over its local 98th percentile: 30 m/s in Brittany is not exceptional, 30 m/s in Bavaria is. The cube follows the damage, which grows roughly as the cube of the wind (Klawa & Ulbrich, 2003). The link with the North Atlantic Oscillation is tested here: NAO and European windstorms.

The ERA5 winters are fetched one by one from the Climate Data Store (about ten hours for the first run); the index is computed as soon as the 30 winters of the 1991–2020 reference period are in. No data imported yet. Run: php bin/console --no-debug app:import era5-storms-europe

Method and sources

Data. Daily maximum 10 m gust of the ERA5 reanalysis (Hersbach et al., 2020; daily statistics of the Climate Data Store, maximum of the hourly values), 0.25° grid over 35–72° N and 25° W–40° E, October to March since 1979. Each yearly file is reduced to a 1° grid keeping the strongest gust of the sixteen 0.25° cells, then deleted.

Index. v98 = 98th percentile of the gust of each cell over the October–March days of 1991–2020; each day, index = Σ w × (v / v98 − 1)³ over the cells where v > v98, w = area of the cell relative to a 1° cell at the equator (cos latitude), not normalised, as in Leckebusch et al.: a large storm scores from a few units to a few tens, and north and south add up. Computed over the whole box, north and south of 50° N. Events: consecutive days above the 90th percentile of the daily index, ranked by the sum of their index.

Reading these data

ERA5 gusts are a model diagnostic, not a measurement: less reliable over mountains and coastal relief, and a 1° cell smooths the strongest local gusts. An index relative to the 98th percentile puts a Baltic storm and a Breton one on the same footing; it says nothing of actual damage, which also depends on exposed property. The years 1979–1990 rest on fewer assimilated observations.

SOURCES OF THIS PAGE

Hersbach et al. (2020): Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., et al. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. · doi:10.1002/qj.3803
Licence : Published literature; cited
Leckebusch et al. (2008): Leckebusch, G. C., Renggli, D., & Ulbrich, U. (2008). Development and application of an objective storm severity measure for the Northeast Atlantic region. Meteorologische Zeitschrift, 17(5), 575–587. · doi:10.1127/0941-2948/2008/0323
Licence : Published literature; cited
Klawa et al. (2003): Klawa, M., & Ulbrich, U. (2003). A model for the estimation of storm losses and the identification of severe winter storms in Germany. Natural Hazards and Earth System Sciences, 3(6), 725–732. · doi:10.5194/nhess-3-725-2003
Licence : Published literature; cited
Roberts et al. (2014): Roberts, J. F., Champion, A. J., Dawkins, L. C., Hodges, K. I., Shaffrey, L. C., Stephenson, D. B., et al. (2014). The XWS open access catalogue of extreme European windstorms from 1979 to 2012. Natural Hazards and Earth System Sciences, 14(9), 2487–2501. · doi:10.5194/nhess-14-2487-2014
Licence : Published literature; cited
Pinto et al. (2012): Pinto, J. G., Karremann, M. K., Born, K., Della-Marta, P. M., & Klawa, M. (2012). Loss potentials associated with European windstorms under future climate conditions. Climate Research, 54(1), 1–20. · doi:10.3354/cr01111
Licence : Published literature; cited

European windstorms The great winter storms since 1979, measured by the ERA5 reanalysis