We present a dataset of daily resolution climatic time series that has been compiled for the European Climate Assessment (ECA). As of December 2001, this ECA dataset comprises 199 series of minimum, maximum and/or daily mean temperature and 195 series of daily precipitation amount observed at meteorological stations in Europe and the Middle East. Almost all series cover the standard normal period 1961-90, and about 50% extends back to at least 1925. Part of the dataset (90%) is made available for climate research on CDROM and through the Internet (at http://www.knmi.nl/samenw/eca).A comparison of the ECA dataset with existing gridded datasets, having monthly resolution, shows that correlation coefficients between ECA stations and nearest land grid boxes between 1946 and 1999 are higher than 0.8 for 93% of the temperature series and for 51% of the precipitation series. The overall trends in the ECA dataset are of comparable magnitude to those in the gridded datasets.The potential of the ECA dataset for climate studies is demonstrated in two examples. In the first example, it is shown that the winter (October-March) warming in Europe in the 1976-99 period is accompanied by a positive trend in the number of warm-spell days at most stations, but not by a negative trend in the number of cold-spell days. Instead, the number of cold-spell days increases over Europe. In the second example, it is shown for winter precipitation between 1946 and 1999 that positive trends in the mean amount per wet day prevail in areas that are getting drier and wetter.Because of its daily resolution, the ECA dataset enables a variety of empirical climate studies, including detailed analyses of changes in the occurrence of extremes in relation to changes in mean temperature and total precipitation.

Long‐term in situ observations are widely used in a variety of climate analyses. Unfortunately, most decade‐ to century‐scale time series of atmospheric data have been adversely impacted by inhomogeneities caused by, for example, changes in instrumentation, station moves, changes in the local environment such as urbanization, or the introduction of different observing practices like a new formula for calculating mean daily temperature or different observation times. If these inhomogeneities are not accounted for properly, the results of climate analyses using these data can be erroneous. Over the last decade, many climatologists have put a great deal of effort into developing techniques to identify inhomogeneities and adjust climatic time series to compensate for the biases produced by the inhomogeneities. It is important for users of homogeneity‐adjusted data to understand how the data were adjusted and what impacts these adjustments are likely to make on their analyses. And it is important for developers of homogeneity‐adjusted data sets to compare readily the different techniques most commonly used today. Therefore, this paper reviews the methods and techniques developed for homogeneity adjustments and describes many different approaches and philosophies involved in adjusting in situ climate data. © 1998 Royal Meteorological Society

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. ; : : , , _ 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 Bight. 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.

No abstract

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. ; : : , , _ 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 Bight. 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.