Day‐to‐day temperature variability trends in 160‐ to 275‐year‐long European instrumental records

Abstract

Day‐to‐day temperature variability is investigated in eight European series of daily mean temperatures beginning between 1722 and 1833. Eight statistical measures of day‐to‐day temperature variability are compared. The intramonthly standard deviation of daily temperature anomalies is found to be a good measure. The absolute change in temperature anomaly from one day to the next is sensitive to changes in observational procedures and is suggested as a diagnostic tool for identification of inhomogeneities in instrumental temperature series. Because many changes in observational procedures have taken place, quantitative estimates of trends in day‐to‐day variability, based on all series, could only be calculated for 1880–1998. A trend analysis over this period indicates an increase by 5% in southwest Europe, 0 to −5% change in the northwest, and a decrease by 5 to 10% in northeast Europe. On a longer time perspective, day‐to‐day temperature variability in winter, spring, and autumn in northern Europe has decreased over the last 200–250 years. The frequency of extremely cold winter days in northern Europe was lower in the twentieth century than in the eighteenth and nineteenth centuries. Day‐to‐day temperature variability in winter in northern Europe was negatively correlated with a North Atlantic Oscillation index in the period 1826–1997, but some other factor must also have contributed to the long‐term variability decrease. More long daily temperature series, and development of homogenization methods for such data, are needed for an improved knowledge of long‐term changes in day‐to‐day temperature variability.