Réf. Bárdossy & al 2003 - E

Référence bibliographique complète
BÁRDOSSY, A., ANAGNOSTOPOULOU, C., CACCIAMANI, C., CASPARY, H., FREI, C., GOODESS, C., HAYLOCK, M., HUNDECHA, Y., MAHERAS, P., MICHNA, P., PAVAN, V., PLAUT, G., SCHMIDLI, J., SCHUEPBACH, E., SIMONNET, E., TOLIKA, K., TOMOZEIU, R. Trends in extreme daily precipitation and temperature across Europe in the 2nd half of the 20th century. Deliverable D9 of STARDEX project : STAtistical and Regional dynamical Downscaling of EXtremes for European regions, 2003.

Abstract: This study is aimed at investigating the evolution of extreme precipitation and temperature over the second half of the 20th century across Europe. Consistent statistical approaches were applied to observed daily precipitation and temperature data series from well selected observation stations across the entire region and from denser station networks in different sub-regions to find out whether there have been any changes in the extremes over the period under investigation. Whether the changes are significant and they have any seasonal dependence have also been investigated.


Organismes / Contacts

University of East Anglia, King’s College London, Fundación para la Investigación del Clima, University of Berne, Centre National de la Recherche Scientifique, Servizio Meteorologico Regionale, ARPA-SMR Emilia-Romagna, University of Bologna, DMI : Danish Meteorological Institute, Swiss Federal Institute of Technology, Fachhochschule Stuttgart – Hochschule für Technik, Institut für Wasserbau, University of Thessaloniki, Greece. http://www.cru.uea.ac.uk/projects/stardex/

(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
Temperature, Extreme Precipitations      

Pays / Zone
Massif / Secteur
Site(s) d'étude
Période(s) d'observation
Europe (only results for Switzerland, Germany, Northern Italy and France are cited here) Whole Switzerland, parts of the Rhine basinin Germany, Emilia-Romagna in Northern Italy, Savoy, Queyras, the Alps Maritimes, and Roussillon sub-regions for France        

(1) - Modifications des paramètres atmosphériques
Extreme Precipitation:

Switzerland: In Switzerland, the indices related to heavy precipitation generally show significant increases in winter and autumn, while they show weak positive trends in the summer and spring. No significant change was obtained for the maximum number of consecutive dry days.

Germany: In Germany, heavy precipitation indices show significant increases in winter and significant decreases in summer. They show more positive trends in spring and autumn, with many stations having significant trends. But there are also a lot of stations with negative trends, although not significant. The maximum number of consecutive dry days shows a strong negative significant trend in autumn and a positive trend in summer. In spring, positive and negative trends are balanced, with few significant station series. In winter there is no significant change, although the trends tend to be negative.

Northern Italy:
In Northern Italy, the indices related to heavy precipitation show negative trends in winter and spring, while they show opposite trends in summer. The maximum number of consecutive dry days increased only in winter, with no change observed in other seasons.

For France, investigation was made on one station series for each of the regions Queyras, Alps maritime, and Roussillon and additionally gridded precipitation time series for the alpine region synthesised by the ETH. For Savoy, only precipitation from the gridded series was used. In Savoy, all heavy precipitation related indices show an increasing trend in all seasons with significant increase in winter. The maximum number of consecutive dry days shows weak positive trends in all seasons. In the Alps maritime, many of the indices show a significant decrease in spring and summer, while they show poorly significant changes in winter. In autumn, a few significant positive trends are observed. In Queyras, signals of significant increase in some heavy precipitation indices are noticed in spring and winter. The total accumulated precipitation shows a slight increase in spring and autumn. The maximum number of dry days also increases in spring and decreases in autumn. In Roussillon, decreasing trends are noticed for a few indices in spring. Generally, stations located in the north of the Alps get more intense precipitation in all seasons except summer and the corresponding increase in the extreme indices was found to be highly significant, especially in winter. In the south of the Alps, significant increases in some of the extreme indices were obtained only in autumn.

Extreme Temperature:

Switzerland: In Switzerland, there is a clear increase in the minimum extreme temperature in all seasons except autumn. The increase was found to be significant in western and southern Switzerland. In autumn, there is a balance between the number of stations showing an increase and a decrease. The maximum extreme temperature shows an increase at almost all stations in winter, half of them significant. A nearly similar pattern is observed for spring, but fewer stations show a significant increase. Most stations show an increasing trend in summer, although non significant. In contrast, most stations show a negative trend in autumn. Correspondingly, the number of frost days shows a negative trend for most stations in winter and spring, though the number of significant decreases in spring is less. In autumn, the number of stations with a positive trend is greater than those showing a negative trend. No clear pattern was obtained in the trend of the heat wave duration index. Generally, most stations show an increasing trend in summer and winter and a decreasing trend in spring and autumn.

Germany: In Germany, the maximum temperature has increased significantly in all seasons except in autumn, where the increase is balanced by the decrease. The minimum temperature has also displayed a significant positive trend in spring and summer, while a balance between positive and negative trends is observed for the other seasons with little statistical significance. The number of frost days has shown a significant decrease in winter and spring, while a balance between an increase and a decrease was noticed in other seasons. The heat wave duration index has also increased in all seasons, with the strongest significant increase in winter.

Northern Italy:
In Northern Italy, a warming signal is evident in all seasons, with both the maximum and minimum temperatures displaying positive trends. The number of frost days has also decreased in winter and spring, although not significantly. No trend was obtained in autumn for this index. The heat wave duration index has also increased, with the most intense increase observed in summer.

In France, detailed investigation was made at three stations: Nice (Alps maritime), Embrun (Queyras), and Perpignan (Roussillon). Twenty more French stations in other parts of France were also investigated to see whether the observations made in the Alpine area are similar with those of the other regions. At Nice, the maximum temperature shows an increase in all seasons, but a highly significant increase was observed in summer. The minimum temperature shows a significant increase in all seasons except in autumn, where the increase is not significant. At Embrun, except for a significant increase of the maximum temperature in summer, only winter indices show a significant warming signal. They show no change in autumn. At Perpignan, little sign of warming was obtained. The observations for the 20 French stations indicate that the trend pattern for the maximum extreme temperature is more like the observations at Embrun and for the extreme minimum temperature, it is more like those at Nice.

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

Daily time series of precipitation and maximum and minimum daily temperatures were collected from a number of representative stations within the study areas. The time period for the study was set between 1958 and 2001, but for some of the study areas the period extended back to as early as the beginning of the 20th century, as in the case of Switzerland. In addition, both precipitation and temperature extremes were analyzed for Europe as a whole using data from 481 stations for the period 1958 to 2000.

As the study was focused mainly on the changes in extremes, a number of extreme temperature and precipitation indices were defined. Many of the indices are based on thresholds defined on the basis of statistical quantities such as the 90th or the 10th percentiles. The base period for the calculation of such quantities was set between 1961 and 1990. This makes the indices applicable to a wide variety of climates as no arbitrary threshold values are used. The only exception is a fixed threshold value of 0°C used to define frost days; which is, of course, applicable to all climates.

STARDEX Diagnostic Extreme Indices analysed in the study:

Precipitation related indices
- 90th percentile of rainday amounts (mm/day)
- Greatest 5-day total rainfall
- Simple Daily Intensity (rain per rainday)
- Max no. of consecutive dry days
- % of total rainfall from events > long-term 90th percentile
- No. of events > long-term 90th percentile of raindays

Temperature related indices
- Tmax 90th percentile
- Tmin 10th percentile
- Number of frost days Tmin < 0 °C
- Heat wave Duration

(2) - Effets du changement climatique sur le milieu naturel

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)


(3) - Effets du changement climatique sur l'aléa

Paramètres de l'aléa
Sensibilité du paramètre de l'aléa à des paramètres climatiques et du milieu / Facteurs de contrôle
Informations complémentaires (données utilisées, méthode, scénarios, etc.)

(4) - Remarques générales

Results of the analysis of observed trends both at the European-wide scale and at local scales for the different study areas are presented and discussed in detail in the separate reports contributed by partners on their respective sub-regions - available from the STARDEX web site. A general summary of the results, focusing on winter and summer, is also presented.

See also individual partner contributions from UEA (for Europe and UK), UNIBE, CNRS, ARPA-SMR, ETH, FTS, USTUTT-IWS and AUTH – available from http://www.cru.uea.ac.uk/cru/projects/stardex/.

(5) - Syntèses et préconisations
As summarised in the previous sections and shown in more detail in the partner contributions, the trends for most of the investigated indices show spatial variation. Analysis of stations distributed over the entire European region indicates that stations showing an increase and a decrease in the extreme precipitation indices show coherent spatial structure across Europe, with consistent trends in the indices describing similar extreme conditions. On average, heavy precipitation conditions have increased in winter, while little change has been observed in summer. Although the spatial coherence of the trends in the extreme temperature indices is not as clear as that of the extreme precipitation indices, it has, in general, been found that both the extreme maximum and minimum temperatures have increased across the European region, with the minimum showing more increase than the maximum.