Interannual variability of European extreme winter rainfall and links with mean large-scale circulation (original) (raw)
Related papers
2004
December–February (DJF) extreme rainfall was analysed at 347 European stations for the period 1958–2000. Two indices of extreme rainfall were examined: the maximum number of consecutive dry days (CDD); and the number of days above the 1961–90 90th percentile of wet-day amounts (R90N). A principal component analysis of CDD found six components that accounted for 52.4 % of the total variance. Six components of DJF R90N were also retained that accounted for 39.1 % of the total variance. The second component of R90N has a very significant trend and the factor loadings closely resemble the observed linear trend in this index, suggesting that the analysis has isolated the mode of variability causing the trend as a separate component. The principal components of the indices were correlated with surface and upper-air observations over the North Atlantic. The best correlations were generally found to be with sea-level pressure (SLP) observations. A separate canonical correlation analysis of ...
A growing interest in extreme precipitation has spread through the scientific community due to the effects of global climate change on the hydrological cycle, and their threat to natural systems' higher than average climatic values. Understanding the variability of precipitation indices and their association to atmospheric processes could help to project the frequency and severity of extremes. This paper evaluates the trend of three precipitation extremes: the number of consecutive dry/wet days (CDD/CWD) and the quotient of the precipitation in days where daily precipitation exceeds the 95th percentile of the reference period and the total amount of precipitation (or contribution of very wet days, R95pTOT). The aim of this study is twofold. First, extreme indicators are compared against accumulated precipitation (RR) over Europe in terms of trends using non-parametric approaches. Second, we analyse the geographically opposite trends found over different parts of Europe by considering their relationships with large-scale processes, using different teleconnection patterns. The study is accomplished for the four seasons using the gridded E-OBS data set developed within the EU ENSEMBLES project.
Space-time structure of extreme precipitation in Europe over the last century
International Journal of Climatology, 2014
We investigate the space-time structure of extreme precipitation in Europe over the last century, using daily rainfall data from the European Climate Assessment & Dataset (ECA&D) archive. The database includes 267 stations with records longer than 100 years. In the winter season (October to March), for each station, two classes of daily rainfall amount values are selected that, respectively, exceed the 90th and 95th percentile of daily rainfall amount over all the 100 years. For each class, and at each location, an annual time series of the frequency of exceedance and of the total precipitation, defined respectively as the number of days the rainfall threshold (90th and 95th percentiles) is exceeded and total precipitation on days when the percentile is exceeded, are developed. Space-time structure of the frequency and total precipitation time series at the different locations are then pursued using multivariate time and frequency domain methods. The identified key trends and organized spectral modes are linked to well-known climate indices, as North Atlantic Oscillation (NAO) and El Nino Southern Oscillation (ENSO). The spectra of the leading principal component of frequency of exceedance and of total precipitation have a peak with a 5-year period that is significant at the 5% level. These are also significantly correlated with ENSO series with this period. The spectrum of total rainfall is significant at the 10% level with a period of ∼8 years. This appears to be significantly correlated to the NAO index at this period. Thus, a decomposition of both secular trends and quasi-periodic behaviour in extreme daily rainfall is provided.
Climate Research, 2017
Seasonal trends in extreme precipitation indices were investigated for 30 yr moving periods between December 1950 and February 2008. To update the 2008 to 2015 data, supplementary calculations were performed for >120 meteorological stations. A linear regression of the least squares method was used to calculate trend magnitudes. Trend significance was tested using the Mann-Kendall method. Changes in short-term trend frequency and temporal coherence were assessed. Extreme precipitation was defined as a daily amount exceeding the 95th percentile, calculated separately for each month and station using daily totals ≥1 mm. The spatial pattern of extreme precipitation trends varied by season. Significant extreme precipitation trends were rare, constituting approximately 25 to 30% of all analysed trends, and were seldom temporally coherent. Most of these significant trends were upward, except in summer, when a nearly equal frequency of positive and negative trends was found. Increases in the frequency and the total were a characteristic feature of extreme precipitation changes, particularly in winter. Seasonal variations in the spatial patterns of extreme precipitation trends may have resulted from seasonal changes in the prominence of the driving factors of precipitation. In spring, upward trends in Central and Western Europe were twice as frequent as the downward trends found primarily in Southern Europe. In summer, the percentages of significant downward trends in Western Europe and upward trends in Eastern Europe were similar. In autumn, a coherent decrease in extreme precipitation was clear in Central Europe. The spatial distribution of trend directions was the most consistent in winter.
Nonseasonal variability of monthly mean sea level pressure and precipitation variability over Europe
Physics and Chemistry of The Earth Part B-hydrology Oceans and Atmosphere, 2000
The spatial modes of nonseasonal variability in both monthly mean sea level pressure (MSLP) fields over the northeastern Atlantic and western Europe sector and precipitation over Europe are investigated by using principal component analysis (PCA). The relationships between the two fields are revealed by canonical correlation analysis (CCA). The data sets used refer both to the period from 1911 to 1990. The most important spatial mode in MSLP fields is the NAO pattern and its corresponding principal component (PC) is closely related to the NAO index. However, it is interesting that the NAO pattern seems to be responsible only for the second EOF in precipitation while the most important spatial mode of precipitation corresponds to the third EOF of MSLP (North Sea pattern). Furthermore, the second EOF (Scandinavian pattern) of MSLP is highly associated with the third EOF in precipitation.
Interannual oscillations in winter rainfall over Europe. Iberia study case
Finisterra, 2012
Low -frequency variability is a good starting point for modelling the climate system and understanding mechanisms that can give us some indication of future climate evolution. this work aims to better understand the degree of association between the atmospheric circulation and precipitation over europe and the iberian Peninsula. to achieve this goal, the standard precipitation anomalies in europe and the anomalies of sea level pressure (sLP) in the north atlantic region during the twentieth century were subjected to Multi -Channel singular spectrum analysis (Mssa). this procedure allows us to measure the degree of association between the sLP and precipitation fields. the identification of common oscillations between the two climatic fields led not only to the confirmation of the physical meaning of these oscillations, but also to the identification of the dynamical evolution of the ocean -atmosphere system in the north atlantic. two oscillations, statistically significant, common to...
International Journal of Climatology, 2002
This paper assesses the relationship between a regional index of rainfall (SWER) over Devon and Cornwall, South-west England, and concurrent gridded (5°× 5°) sea-surface temperature anomalies (SSTAs) for the North Atlantic-European domain (10-70°N, 80°W-20°E) over the period 1950-97. Monthly and seasonal SSTA : SWER correlation fields are derived, and stepwise regression models are then constructed to specify SWER through SSTA variations. In particular, this paper emphasizes the importance of assessing all correlation matrices for field significance, an analysis stage that is often ignored by many researchers. The most temporally reproducible signal is found between depressed SSTs to the west of the British Isles and above-average rainfall over Devon and Cornwall, although this eastern Atlantic signal is by no means constant over time in terms of its location and spatial extent. Another distinctive feature of the anomaly correlation maps is for locally significant positive SSTA : SWER associations to emerge at high latitudes (60-70°N) in summer and early autumn, e.g. Davis Strait, Norwegian Sea. Field significance testing reveals that seasonal SSTA : SWER correlation fields are statistically more robust than their monthly counterparts. This is demonstrated by the fact that the seasonal fields (excluding summer) all achieve field significance at the 0.1 level, whereas only five of the 12 monthly fields (January, May, July, October and December) do so, suggesting that some of the locally significant SSTA : SWER correlations presented in this paper could have been obtained by merely correlating SWER with a random number series.
Journal of Geophysical Research, 2000
Signatures of the North Atlantic Oscillation (NAO) are widely detected in climatic variability, particularly in the extratropical latitudes surrounding the North Atlantic Ocean. However, it is still controversial whether the NAO is the most important pattern of nonseasonal variability of atmospheric circulation related to precipitation over Europe. This paper is an attempt to contribute to this issue. The spatial modes of nonseasonal variability of monthly fields of mean sea level pressure (MSLP) over the northeastern Atlantic and western Europe and precipitation over Europe are investigated mainly by using principal component analysis. The relationships between the two fields are studied via canonical correlation analysis (CCA). The data sets used refer to the period from 1911 to 1990. The most important spatial mode of MSLP is the NAO pattern, its corresponding principal component being closely related to the NAO index. Interestingly however, the NAO pattern seems to be responsible only for the second empirical orthogonal function in precipitation, while the most important spatial mode of precipitation corresponds to the third EOF of MSLP (North Sea pattern). Furthermore, the second EOF of MSLP (Scandinavian pattern) is highly associated with the third EOF of precipitation. Significant pairs of canonical patterns between the MSLP and precipitation fields obtained from canonical correlation analysis are coherent with the conclusions above. These results can potentially be used to assess possible changes of precipitation over Europe due to increasing greenhouse gases based on the variability of MSLP simulated by general circulation models.
Climate Dynamics, 2018
The connections between European rainfall variability in winter (from January to March) and Northern Hemisphere circulation patterns, as represented by 500-hPa geopotential height, are investigated in the period 1900-2014. Initially, three statistically significant pairs of linearly-related circulation and precipitation patterns, explaining 45% of the variance in the latter field, are identified. The first two essentially represent the North Atlantic Oscillation (NAO) and the East Atlantic (EA) patterns, while the third corresponds to a structure described in recent literature as a blend of the Pacific North America (PNA) pattern and the so-called Asia Bering North America (ABNA) pattern. The residual precipitation field is then examined for patterns that can introduce non-linear modulations into the circulation-precipitation links. It is so found that the NAO impact on European rainfall is modulated by North American and Pacific factors controlling cyclogenesis over Newfoundland. The positive-phase EA rainfall anomalies over Central Europe and the British Isles seem to be markedly affected by the NAO phase. Finally, a possible signature from the Circumglobal Teleconnection Pattern disrupting the NAO influence on East Mediterranean precipitation anomalies is detected.