An assessment of changes in seasonal and annual extreme rainfall in the UK between 1961 and 2009

Abstract

There is a growing body of evidence supporting the Intergovernmental Panel on Climate Change's contestation that changes to hydrological extremes as a result of anthropogenic climate change are likely. There is also a growing level of concern among water resource managers about the nature of these changes and how we might adapt our behaviour to accommodate them. In particular, extreme multi-day rainfall events have been a significant contributing factor to the severe flood events of recent years.Here we provide an updated study of extreme rainfall in the UK, focussing on changes to seasonal and annual maxima over the period 1961-2009. We employ regional frequency analysis to examine changes in the magnitude of estimated return periods obtained from generalized extreme value distribution curves. Return period estimates are analysed using both the full record and using 10 year intervals to determine the relative importance of natural variability and long-term changes in extreme rainfall distribution.The magnitude of changes in estimated return periods are spatially varied, and dominated in northern and western parts of the UK by a periodic forcing such as the North Atlantic Oscillation (NAO), superimposed on normal seasonal fluctuations. In contrast, seasonality has the greatest influence on event magnitude in the south and east. We confirm that previously reported increases in spring and autumn extreme rainfall events have continued. Similarly, longer duration winter events have continued to increase in intensity, with a decrease in return period estimate from a 25-year to around a 5-year event over the full 50 years of record in parts of Scotland and Southwest England. In contrast, short-duration summer rainfall events have continued to decline in intensity, whereas longer duration events appear to be increasing in intensity. These results may have significant implications for flood defence design and planning, as well as to agricultural practices which may be sensitive to extreme rainfall.

The Value of High-Resolution Met Office Regional Climate Models in the Simulation of Multihourly Precipitation Extremes

“…This is facilitated by the widespread availability of qualitycontrolled daily precipitation datasets, such as the Met Office (UKMO) National Climatic Information Centre (NCIC) daily gridded precipitation (Perry et al 2009), which is available for the United Kingdom at a high resolution (5 km) for 501 years. As a consequence, UK daily precipitation extremes have been well characterized (Fowler and Kilsby 2003a,b;Maraun et al 2009Maraun et al , 2011Atyeo and Walshaw 2012;Jones et al 2013).…”

Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK

“…Laizé and Hannah (2010) also discuss the importance of studying trends not only in the annual series but also dividing the data into different seasons. Trends in UK extreme rainfall data have been studied by Jones et al (2013) who reported an increase of intensity in long-duration events, but a decline in intensity for short-duration summer rainfall. Jenkins et al (2008) also report a decrease in rainfall during the summer season and an increase in winter rainfall, with a particular increase of high-rainfall events in winter.…”

Frequency analysis, infilling and trends for extreme precipitation for Jamaica (1895–2100)

“…The existing curves, however, neither account for historical data now available from 1895 to 1957 nor for recent continuous gauge data from 1992 to 2010. The curves are also limited to 24 h durations and shorter, although longer durations of 2-10 days are useful for assessing severe flood events and for evaluating climate change (Jones et al, 2013;Jones, 2012). Additionally, the goodness of fit for the existing IDF curves and its derivation were not stated in the report by the UWA (1995).…”