Trends of mean and extreme temperature indices since 1874 at low‐elevation sites in the southern Alps. Issue 7 (8th April 2016)

• Record Type: Journal Article
• Authors: Brugnara, Yuri; Auchmann, Renate; Brönnimann, Stefan; Bozzo, Alessio; Berro, Daniele Cat; Mercalli, Luca
• Is Part Of: Journal of geophysical research. Volume 121:Issue 7(2016)
• Page Start: 3304
• Page End: 3325
• Publication Date: 2016-04-08
• Subjects: homogenization -- climate change -- temperature -- extremes; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2015JD024582
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: We describe the recovery of three daily meteorological records for the southern Alps (Domodossola, Riva del Garda, and Rovereto), all starting in the second half of the nineteenth century. We use these new data, along with additional records, to study regional changes in the mean temperature and extreme indices of heat waves and cold spells frequency and duration over the period 1874–2015. The records are homogenized using subdaily cloud cover observations as a constraint for the statistical model, an approach that has never been applied before in the literature. A case study based on a record of parallel observations between a traditional meteorological window and a modern screen shows that the use of cloud cover can reduce the root‐mean‐square error of the homogenization by up to 30% in comparison to an unaided statistical correction. We find that mean temperature in the southern Alps has increased by 1.4°C per century over the analyzed period, with larger increases in daily minimum temperatures than maximum temperatures. The number of hot days in summer has more than tripled, and a similar increase is observed in duration of heat waves. Cold days in winter have dropped at a similar rate. These trends are mainly caused by climate change over the last few decades. Key Points: Three new daily instrumental series dating back to the late nineteenth century are presented Cloud cover is a valuable constraint for the homogenization of daily temperature series Summer hot days in the southern Alps have increased by over 200% in the last 140 years