Rescue of historical snowfall data collected in the Italian Apennines

Over the last decades, increasing attention has been directed toward the investigation of historical snowfall variability on a global scale, with a particular focus on mountainous regions. Snow represents a fundamental element of the hydrological cycle and plays a key role in the Earth’s energy balance by regulating surface albedo. Moreover, it exerts a strong influence on mountain ecosystems and on biogeochemical processes. In the context of ongoing climate change, which is increasingly threatening the cryosphere and high-altitude environments, the reconstruction and analysis of long-term historical snowfall records are essential to evaluate past variability and identify prevailing trends.

However, for several reasons, many mountain areas remain under-researched. In the Mediterranean, an example in this sense is represented by the Apennine region (Italy). A considerable lack, in fact, exists in the knowledge of the past snowfall variability for this area, although it has a good heritage of past in situ observations.

In this context, the present work seeks to partially bridge this gap by rescuing historical snowfall measurements collected in the Apennines. More specifically, the recovered dataset consists of monthly observations of the three snow-related variables, i.e. snow cover duration, number of days with snowfall and total height of new snow, collected at 395 stations located between 288 and 2165 m a.s.l. The data, originally available as scanned images in portable document format, have been digitized following the World Meteorological Organization standard practices. After a cross-check, the digitized data went through three different quality control tests: the gross error test, which verifies whether the data are within acceptable range limits; the consistency test, which involves an inter-variable check; and the tolerance test, which is focused on outlier detection. In addition, the available time series were subjected to homogenization tests using the Climatool toolbox.

The result of this process is a new historical dataset that includes digitized and quality-controlled snow-related observations collected from 1951 to 2001 in the Apennines. These data are critical to enhancing and complementing previously rescued historical datasets in the mountain regions and constitutes an added value for research focused on the comprehension of climate dynamics in mountainous areas, as well as on future changes in snow precipitation in the Mediterranean region.