DER AUSBRUCH DES VULKANS TAMBORA 1815 UND DIE DOKUMENTATION VON SONNENFLECKEN AM STIFT ADMONT IM RAHMEN ZEITGENÖSSISCHER METEOROLOGISCHER BEOBACHTUNGEN.

When the Tambora volcano erupted in Indonesia in 1815 with the highest intensity ever measured in Modern Times, this had consequences for the whole world. This paper will not deal with the negative consequences such as climate deterioration or crop failures, but with a positive side effect: the increased atmospheric opacity caused by the volcanic eruption made observations of sunspots easier. At that time, the now confirmed assumption that there is a connection between sunspot activity and climate was discussed. Regular observations were required for confirming this hypothesis. At the Benedictine monastery in Admont (Styria) the first meteorological measurements were carried out by the monk and physicist Gotthard Wisiak in the years 1814-1818. During his recordings, which were carried out three times a day, Wisiak noted various climatic elements and sunspot phenomena. The latter form the focus of this contribution. Although Wisiak's observations fall within the so-called "Dalton Minimum" (ca. 1790--1820), a period of low sunspot activity, the year 1816 was well suited for such observations because the maximum of solar cycle 6 was in that year. Wisiak mentioned the term sunspot 64 times in his records, including 9 times of explicit absence and 55 times of sightings of them. The recorded number of sunspots varied between 1 and 30. Also sunspot formations like an "army" (meaning a rather large group of sunspots) were mentioned. According to Wisiak's meteorological data, the observations of sunspots were in most cases carried out at conditions with high air humidity causing additional opacity. Quantitative comparisons with contemporary sunspot studies by Augustin Stark (Augsburg, Germany) and Thaddäus Derfflinger (Kremsmünster, Upper Austria) show overall consistency with the Admont observations especially for the period July to October 1816, despite different sophisticated instruments, topographical constraints at Admont, and the difference between primary (focus on astronomical monitoring) and secondary (focus on meteorological monitoring) sunspot observation activities. This contribution thus also gives new hints on the evaluability of historical sunspot observations in Austria based on primarily meteorologically oriented archive records. [ABSTRACT FROM AUTHOR]