Daily Weather Observations in Sixteenth-Century Europe
By Christian Pfister, Rudolf Brázdil, Rüdiger Glaser, Anita Bokwa, Franz Holawe, Danuta Limanowka, Oldřich Kotyza, Jan Munzar, Lajos Rácz, Elisabeth Strömmer, Gabriela Schwarz-Zanetti
Climatic Change, Vol. 43 (1999)
Abstract: Thirty-two weather diaries written in astronomical calendars in central Europe in the late fifteenth and sixteenth centuries are presented and discussed. Systematic weather observations were promoted by the rise of planetary astronomy and its application in astro-meteorology. The practice of keeping weather diaries spread from Cracow (Poland) to Ingolstadt (Germany) and from there to other universities. The data obtained from these sources provided the backbone for setting up series of precipitation indices for Poland, Germany and Switzerland. Month1y statistics of days with precipitation, snowfall and frost were computed by counting the relevant entries in the most important diaries. The results were compared with either those obtained from instrumental measurements in the same place or with those from modem instrumental measurements in a neighbouring place.
The final results show that autumn was considerably colder in the early sixteenth century. April was considerably drier and July was wetter during the period 1508-1531 than during 1901-1960. In order to highlight the impact of weather patterns on grain prices in a year of crisis, the timing of wet and dry spells in southern Poland and southern Germany is compared for the year 1529. Winters became 1.7°C colder from 1564 to 1576 and the month of July tended to be wetter than in 1901-1960. Details noted in the diaries kept between 1585 and 1600 by the astronomers Brahe (near Copenhagen) and Fabricius (in the Ostfriesland region of northwestern Germany) closely agree. It rained more often in June and July and temperatures dropped. The winter months were more frequently dominated by winds from easterly directions, the frequency of snowfall was higher and a deficit occurred in precipitation. This points to a higher frequency of high pressure in the Fennoscandian area with cold air advection from the east or northeast.
The earliest known daily weather observations in Europe – for the brief period 1269-1270 – appear in a volume written by Roger Bacon (ca. 1214-1294), one of the forerunners of empirical methods in scientific studies. The Reverend William Merle in Lincolnshire (England) kept a weather diary from January 1337 to January 1344. A further journal, covering the period 1399-1405, is anonymous. It belonged to a Dominican monastery in the town of Basle (Switzerland) and is now in the manuscript collection of the university library there. It is not clear whether the observations recorded therein were made in Basle or in the adjacent region of France. In Japan, several weather diaries were already being kept from about AD 1000.