Vær og klima over indre strøk av Østlandet 1781 - 1790

Abstract

Each of the four observers, Hans Strøm, Christian Sommerfelt, Axel Christian Smith and Hans Jacob Wille, is presented with a short biography, followed by their respective observations. Strøm’s observations also include instrumental readings of air pressure and temperature. e instrumental readings have been converted into modern units and their representativity has been discussed. e observations form the basis for a discussion of circulation, weather and climate during the decade 1781-1790 for Southern Norway month by month. For the pentade 1781-1785 the observations of the four observers are generally in good accordance with the well-known daily historical weather maps carried out by Dr. John Kington (Kington 1988) for this period. As part of this pentade, observations of volcanic ashes from the eruption of Laki in Iceland during the summer 1783, and certain meteorological implications as observed by three of the four observers, are discussed in relation to regional and general circulation. In the pentade 1786-90 sketches of main features of regional circulation patterns over Eastern Norway for individual days have been made and discussed on the basis of Strøm’s observations and other Nordic historical sources. “Stor-Ofsen” – the catastrophic rain flood in Gudbrandsdalen and Østerdalen in July 1789 – is discussed separately based on Dr. John Kington’s historical weather maps prepared especially for this event (Kington 1979). An index table on a scale between 0 and +/- 2 is presented for Eastern Norway, indicating the author’s suggestions of deviations of the monthly mean temperatures of the decade 1781-90 from the normals of the period 1961-90. A table of indexes in a scale from 0 to +/-2 is presented for Eastern South Norway indicating deviations of the monthly mean temperatures from those which the observers experienced as normal means of their own times.