Daily precipitation variability in the southern Alps since the late 19th century

Abstract

We analysed a data set of 18 homogenized daily precipitation series from the southern European Alps, covering approximately the last 150 years. Previously available data from stations in Northern Italy have been extended considerably by recent digitization work, and, for the first time, they have been combined with daily data from Swiss stations on a centennial scale. Precipitation frequency in the southern Alps decreased significantly over the period 1890–2017. We show that this trend is related to a step‐like reduction in cyclonic weather types over central Europe that occurred around 1940. This decrease is an example of the large variability that affects precipitation in the region over many different time scales. In particular, strong trends on a decadal scale are related to the Atlantic Multidecadal Oscillation and the North Atlantic Oscillation, although the influence of the latter is present only in the recent decades. Trends in heavy precipitation indices do not show a coherent pattern across the study area. We find a significant increase in heavy precipitation in Switzerland, while a decrease affects the southeastern subset in spring.

A multi‐century meteo‐hydrological analysis for the Adda river basin (Central Alps). Part I: Gridded monthly precipitation (1800–2016) records

“…After this decade, however, spring precipitation returns to be rather low, with another very severe drought at the beginning of the 21st century (see also Figure 8), and it shows significant negative trends even over 100‐year long periods starting around the 1910s. This spring trend is also highlighted by Brugnara and Maugeri (2019).…”

A multi‐century meteo‐hydrological analysis for the Adda river basin (Central Alps). Part II: Daily runoff (1845–2016) at different scales

“…Specifically, we used the record available at NOAA ESRL (https://www.esrl.noaa.gov/ psd/data/timeseries/AMO/). Some recent papers (see e.g., Zampieri et al, 2017;Brugnara and Maugeri, 2019) seem to indicate a relevant influence of this index on alpine precipitation. However, in our data, we found a significant positive correlation of AMO with precipitation only for the month of July (ρ = 0.155).…”

Causes of increased flood frequency in central Europe in the 19th century

“…Opposite anomalies, i.e., positive GPH anomalies and descent, are found for the flood-poor period, which was in fact associated with heat waves and strong droughts in central Europe. Brugnara and Maugeri (2019) find a regime shift in total precipitation and wet-day frequency for a southern region of the Alps and for a period after the 1940s which coincides with the flood-poor period.…”

“…To corroborate our results, we also consulted the Twentieth Century Reanalysis, version 2c (20CRv2c; Compo et al, 2011). Specifically, we used daily data of precipitation, precipitable water (PWAT), and u wind at 850 hPa for the grid point 48 • N, 6 • E, representing the Basel catchment.…”