Weather, winter severity, Danube floods and low flows at Bratislava in 1435-1595:analysis of daily/weekly resolution weather data in the Bratislava town accounts

Written mainly in German and partly in Latin, the town or chamberlain accounts of historical Pozsony/Pressburg (present-day Bratislava), almost continuously available between 1434-1435 and 1595, contain daily/weekly resolution data on Danube floods, snow and ice cover and occasional data on rainfall, strong winds, (unintentional) fires, cold days and low flows of the Danube. The source provides systematic, annual accounts of incomes and expenses, with only a few years missing: flood and weather related reports were mainly included in the bridge masters’, the ice-cutters’, the ferrymen’s, the town messengers’, and the road and wall maintenance accounts. Furthermore, weather and water-level related information occasionally was also identified in other sections of the accounts, regarding smaller bridges, river transportation, fishing, meadows and hayfields, woods, and other utilities of the nearby island area. Because of the high density of weather and flood data and the available (mainly qualitative) descriptions, it is possible to present a three-scaled index-based quantitative reconstruction of Danube floods and, for some of the years, index reconstructions of winter severity, temperature and precipitation (rainfall, snowfall).

In the presentation, the following major topics are addressed:

• reconstruction of Danube flood intensity (three-scaled), seasonality, and flood types;
• (annual, seasonal) number of intensive rainfall and snowfall events and the (three-scaled) precipitation intensity reconstruction;
• temperature reconstruction, based on three-scaled intensity indices – primarily related to winter;
• weather extremes and corresponding hazards: strong winds and storms, (unintentional) fires, torrential rains (resulting mass erosion);
• documented Danube low-flow events, mainly reflecting on prolonged dry periods in the Upper-Danube catchment.

In the final part of the presentation, long-term climate variability processes are discussed in brief. With applying additional information available in the Bratislava area in other contemporary sources such as charters, letters, a diary (of Zsigmond Torda) and other narratives, it is possible to define periods richer in floods, hard winters and reported extreme events. Apart from the period of the early Spörer solar minimum (1430s-1440s), anomalous periods are identified around the turn of the 15^th and 16^th centuries (ca. 1480s-1510s), in the mid- and late 16^th century.