Early Portuguese meteorological records (18th century)

Abstract

Abstract. Natural proxies, documentary evidence and instrumental data are the main sources used to reconstruct past climates. In this paper, we present the 18th century meteorologists (either Portuguese or foreigners), who made the first observations at several sites in Continental Portugal, Madeira Island and Rio de Janeiro (Brazil), from 1749 until 1802. Information is given concerning observation site, variables observed, measurement period, methodologies and sources (both manuscript and printed). Some examples from the data usefulness are given: rainfall variability in Madeira (1749–1753) and in Continental Portugal (1781–1793) was reconstructed, allowing to extend towards the late 18th century the well known negative correlation between the NAO index and seasonal rainfall. Furthermore, previously unpublished data for 1783–1784 has allowed analysing the consequences of the Laki eruption in Portugal: foggy and haze days are referred to in summer 1783, but unlike the hot summer observed in Northern and Central Europe, temperatures in Portugal were lower than average. Additionally, observations from Rio de Janeiro in Brazil show that the Laki consequences may well have spread to sectors of the Southern Hemisphere. Although the series are short, the data will be used for climate reconstruction studies focused in Southern Portugal and are also useful to improve the quality of large scale reconstruction datasets.