Extreme winds at northern mid-latitudes since 1871

Abstract

Studying a sufficiently large sample of extremes or analysing the statistics of their occurrence, including trends, is hampered by the length of the existing observation-based record. New data sets such as the Twentieth Century Reanalysis (20CR), which consists of an ensemble of 56 members, significantly extend our record back in time. In this paper, we present examples of extremes of winds at northern hemisphere mid-latitudes in 20CR to illustrate challenges and opportunities for analysing extremes over a longer period than previously possible. For four representative storms from Europe and North America, 20CR provides a relatively good depiction of the synoptic-scale meteorological development, although it misses smaller scale features as well as local effects due to orography. For analysing trends of extreme winds, it is shown that the individual ensemble members should be used, rather than the ensemble mean, which appears to be biased towards lower wind speeds early in the record. For the studied locations, decadal variability and trends can best be characterised after around 1950, when the ensemble variance remains consistent. Different methodological approaches for studying changes in extreme winds are discussed. Finally, we show hemispheric maps of trends in extreme wind speeds since 1950.

North Sea Storminess from a Novel Storm Surge Record since AD 1843*

“…Despite the fact that surges measure changes in wind speed and direction, the analysis of high annual percentiles of surges at Cuxhaven confirms earlier observational studies on storminess over the European-Atlantic region with conventional proxies (Schmidt and von Storch 1993;Alexandersson et al 1998Alexandersson et al , 2000B€ arring and von Storch 2004;Matulla et al 2008;Hanna et al 2008;Wang et al 2009) in terms of both variability and trends. Consistent with the different pressure-based storm indices of the last up to 150 yr, periods of increased storminess with higher occurrence of extreme storm surges prevailed at the end of the nineteenth and twentieth century, with very low levels in the 1970s.…”

Quantification of time delay between damages caused by windstorms and by Ips typographus

“…In accordance with the findings of Dobrovolný & Brázdil (2003), a gradual increase in the maximum wind speed for the period 1950−2008 was also demonstrated in Switzerland (Brönnimann et al 2012). Over a similar time span of 1958−2007, forest stand damage in Switzerland was 17 times greater than in the period 1908−1957 and 22 times greater than during 1858−1907 (Usbeck et al 2010).…”

Recent Change—Atmosphere

“…This is corroborated by significant negative trends in the number of days exceeding 7, 8 and 9 Bft (>13.9, 17.2 and 20.8 m s −1 , respectively) in northern Switzerland for the period 1894-1994 (Schiesser et al 1997). The duration of strong winds (>7 Bft) also shows a negative trend for Zürich for 1871-1991 except in winter (Brönnimann et al 2012). Negative trends are also found for central Europe (Matulla et al 2007;Wang et al 2011).…”

“…In contrast, 20CR ) suggests significant upward trends for storminess over data-sparse regions like the NE Atlantic (Donat et al 2011) while Bett et al (2013) did not find a clear trend over Europe. Closer inspection reveals that the agreement of 20CR and wind observations over land like Zürich is reasonable (Brönnimann et al 2012), but there are discrepancies over sea (Krueger et al 2013;Schenk 2015). This is because 20CR, like other reanalyses, assimilates all available pressure observations at a given time step which leads to a strong increase in assimilated land pressure observations (and to a lesser extent also sea pressure observations) over time.…”