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Rebetez, Martine

Nom
Rebetez, Martine
Affiliation principale
Site web
Fonction
Professeure ordinaire
Email
martine.rebetez@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/403

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  • Publication
    Accès libre
    An analysis of the July 2006 heatwave extent in Europe compared to the record year of 2003
    (2009)
    Rebetez, Martine 
    ;
    Dupont, Olivier
    ;
    Giroud, Marianne
    Recent analyses have identified summer warming trends in Europe in recent decades, culminating in 2003, when mean summer temperatures were exceptionally hot over much of Europe. Mean monthly temperatures were very high in July 2003 and reached record levels in both June and August. In 2006, the mean monthly temperature for July reached a record high. Our analysis of temperature observations shows that in July 2006, as in summer 2003, maximum temperatures were more abnormal than minimum values. The 2006 heatwave was located more to the north than in 2003, and particularly affected the Netherlands, Belgium, Germany, Poland, France and Switzerland. The July 2006 anomalies were similar in magnitude to those of June and August 2003, but the discrepancy between minimum and maximum temperature anomalies was larger in 2006 compared to both June and August 2003. For maximum temperature, the affected land area by anomalies higher than 4-6 K was largest in July 2006, although the anomalies were higher in June and August 2003 at the most anomalous sites. In the north of Europe, the absolute monthly temperature values were higher in July 2006 compared to both June (also on the Iberian Peninsula) and August 2003.
  • Publication
    Métadonnées seulement
    Heat and drought 2003 in Europe: a climate synthesis
    (2006)
    Rebetez, Martine 
    ;
    Mayer, Helmut
    ;
    Dupont, Olivier
    ;
    Schindler, Dirk
    ;
    Gartner, Karl
    ;
    Kropp, Jürgen
    ;
    Menzel, Anette
    Heat and drought were extreme in summer 2003 in Europe. Climatic data show that most extreme were maximum air temperatures in June and August; maps of these two months show a striking similarity in geographical range. Over wide regions, monthly mean temperatures were more than 4 degrees C above the long term mean values. The heat lasted from May to September in large parts of western and central Europe. The lack of precipitation was most severe in summer 2003 but precipitation was generally below normal from February 2003 until June 2004 ( with the exception of two months). Sunshine duration was above normal, particularly in regions which usually have rainy and cloudy episodes in summer, and relative air humidity was below normal during the whole year of 2003. The drought experienced by the vegetation in summer 2003 was exacerbated by the length of the period with scarce precipitation and humidity, by the heat during the summer and by long sunshine duration.
  • Publication
    Accès libre
    Summer 2003 maximum and minimum daily temperatures over a 3300 m altitudinal range in the Alps
    (2004)
    Rebetez, Martine 
    The summer of 2003 was extremely hot in Western Europe and in the Alps. Here I analyse the role of elevation in the temperatures measured in 2003, and I compare daytime and nighttime values. Records from 16 stations at varying elevations show that, during the night, there was a significant correlation between heat and altitude. Hot nighttime temperatures were particularly frequent at low elevation. The frequency of unusually hot daytime highs was not correlated with altitude, but with the average degree of insolation of the sites. Compared to long-term averaged values (1961-1990) the temperatures were hottest in the normally sunniest sites. The unusual nature of the 2003 heat wave was not the absolute daily extreme values, but the lack of cool temperatures and the large number of very warm days. Averaged over all climate stations, half of the days in summer were hotter than the 90th percentile (climate normals 1961-1990), with up to 72% at some stations.
  • Publication
    Métadonnées seulement
    To what extent can oxygen isotopes in tree rings and precipitation be used to reconstruct past atmospheric temperature? A case study
    (2003)
    Rebetez, Martine 
    ;
    Saurer, Matthias
    ;
    Cherubini, Paolo
    We analyzed the relationship between air temperature and oxygen isotopes measured in tree rings of silver fir (Abies alba Mill.) from a long-term forest ecosystem research plot in the Swiss Jura mountains (LWF project). The oxygen isotope data were compared with a century-long meteorological series of air temperature data. Measurements of oxygen isotope ratios in precipitation were also used for comparison. Results show that the late-wood tree-ring series is significantly correlated with May to August temperatures. Correlations were higher for maximum (daytime) air temperature and even better for air temperature measured on rainy days only. We stress that trends in maximum temperature series for this time of the year, like trends in oxygen isotope ratios series from tree rings, are completely different from trends in yearly mean temperature. Indeed, maximum temperature trends during the vegetation period slightly decreased during the 20th century, whereas yearly means increased strongly.
  • Publication
    Accès libre
    Changes in daily and nightly day-to-day temperature variability during the twentieth century for two stations in Switzerland
    (2001)
    Rebetez, Martine 
    An analysis of day-to-day variability was performed on two century-longs daily minimum and maximum temperature series from Switzerland. Warmer temperatures during the 20(th) century have been accompanied by a reduction in day-to-day variability, particularly for minimum temperatures and for winter. There is a significant negative correlation between day-to-day variability and the skewness of the temperature distribution, particularly in winter and for minimum temperatures. Lower variability is linked to a reduced number of cold days and nights. Higher NAO index values tend to be associated not only with warmer temperatures but also with lower day-to-day variability. This paper confirms that the temperature warming during the 20(th) century has happened mainly through the loss of the coldest part of the series, not only in the 24-hour or yearly cycle, but also through the loss of the coldest episodes in each month.
  • Publication
    Accès libre
    Progress in the study of climatic extremes in northern and central Europe
    (1999)
    Heino, R
    ;
    Brazdil, R
    ;
    Forland, E
    ;
    Tuomenvirta, H
    ;
    Alexandersson, H
    ;
    Beniston, Martin
    ;
    Pfister, Christian
    ;
    Rebetez, Martine 
    ;
    Rosenhagen, G
    ;
    Rosner, S
    ;
    Wibig, J
    A study of the long-term changes of various climatic extremes was made jointly by a number of European countries. It was found that the changes in maximum and minimum temperatures follow, in broad terms, the corresponding well-documented mean temperature changes. Minimum temperatures, however, have increased slightly more than maximum temperatures, although both have increased. As a result, the study confirms that the diurnal temperature range has mostly decreased during the present century in Northern and Central Europe. Frost has become less frequent. Two extreme-related precipitation characteristics, the annual maximum daily precipitation and the number of days with precipitation greater than or equal to 10 mm, show no major trends or changes in their interannual variability. An analysis of return periods indicated that in the Nordic countries there were high frequencies of 'extraordinary' 1-day rainfalls both in the 1930s and since the 1980s. There have been no long-term changes in the number of high wind speeds in the German Eight. Occurrences of thunderstorms and hails show a decreasing tendency in the Czech Republic during the last 50 years. Finally, using proxy data sources, a 500-year temperature and precipitation event graph for the Swiss Mittelland is presented. It shows large interdecadal variations as well as the exceptionality of the latest decade 1986-1995.
  • Publication
    Accès libre
    Regionalization of precipitation in Switzerland by means of principal component analysis
    (1997)
    Baeriswyl, Pierre-Alain
    ;
    Rebetez, Martine 
    The technique of principal component analysis and of cluster analysis has been applied to two sets of precipitation data in Switzerland, one containing 47 stations (1961-80), and the other 101 stations (1981-1993), with the aim of understanding more fully the spatial distribution of precipitation regimes. Seven regions were highlighted in the first case and 13 in the second. The high spatial coherence which appeared is quite remarkable and confirms the usefulness of these techniques for the analysis of the spatial distribution of meteorological variables, even in a topographically complex area such as Switzerland. The two regional distributions obtained not only correspond fairly well to the large, well-known physical regions of Switzerland, but also go much further, separating the Swiss Plateau into 3 clearly differentiated regions, for example. Regional distributions such as those discussed here can have value for climate change issues, and in particular numerical modeling of climate or climate change impacts on forests.