An Evaluation of Meteorological Observations by Samuel Studer (1807 – 1818)

Early instrumental measurement series contain a vast amount of valuable climatological data. The focus of this study is a series of meteorological measurements and observations conducted by Samuel Studer over 48 years at the Burgerspital in Bern. The period 1807 to 1818 is evaluated within this study. The source itself is critically reviewed and the author is introduced. By thoroughly elaborating on the life of Studer and his social environment, this study works out the motivation behind the lengthy endeavour of noting sub-daily measurements and observations over such a long period. Studer was amongst many during the Age of Enlightenment with an urge to explore and understand nature. He was highly involved in the Oekonomische Gesellschaft Bern. The members of this and other societies were driven to learn more about nature. Meteorological observations became an essential part of their interest, since they aimed to improve their knowledge about agriculture to avoid and combat food crises, as the weather had a direct impact on the food and income situation of many people. The overarching aim of this study is to report on the potential and limitations of the series and to generally make the series more accessible for future research. The temperature and air pressure measurements by Studer underwent a homogeneity assessment. In addition, the precipitation observations are transformed into quantitative data. The homogeneity assessment mainly follows the WMO guidelines. As part of the metadata analysis, information on the instruments used, as well as on their location, position and exposure are investigated. The quality control is performed extremely thoroughly, as many errors as part of the digitization process could be found. For the breakpoint detection, several reference series are used, however, a reference series is only accepted if the Pearson correlation coefficient was higher than 0.6. The homogeneity assessment revealed the general scarcity of metadata available for this time series. Unlike the temperature and air pressure measurements, the precipitation observations are not available quantitatively, but as descriptive notes. Thus, these sub-daily observations are transformed to daily, binary, quantitative data on precipitation events. A major restriction for this process are the missing values, mostly found during the summer months, since Studer was then often travelling to the mountains. The final evaluation, namely, the case study, is eventually based on percentages of precipitation days per month. In addition, the achieved quantitative data is compared to the study conducted by Gimmi et al. (2007) and to the entries in the Euro-Climhist database. Finally, a case study further investigates the climatic consequences of the Unknown Eruption (1808/09) and the eruption of Mount Tambora (1815). The research question, whether the climatic consequences of these eruptions can be found in the Studer series in the two summers following each eruption, is answered by applying hypothesis testing to the monthly temperature, air pressure and precipitation data. The investigated period of 1807–1818 is divided into a reference period and investigated years. The two years following each eruption are considered to be the years perturbed by the volcanic eruptions and thus, are the investigated years. Overall, the study presents the Studer series and makes it more accessible to future research. The main limitations concern the availability of metadata for the entire Studer series and the vast amount of missing values during Studer’s travels (especially in the summer months). The length and high resolution of this series, however, provide a great opportunity to be embedded in studies that also include other early instrumental measurements series of Switzerland; thus, it is a valuable source of information for climate research on the so-called Dalton Minimum at the end of Little Ice Age.