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Drought in Northern Italy: Long Earth Observation Time Series Reveal Snow Line Elevation to Be Several Hundred Meters Above Long-Term Average in 2022
Koehler J, Dietz AJ, Zellner P, Baumhoer CA, Dirscherl M, Cattani L, Vlahović Ž, Alasawedah MH,
The hydrological drought in Northern Italy in 2022 was in large parts the consequence of a lack of snow in the Italian Alps in winter 2021/22 and the resulting deficit of melt water runoff. In this communication we assessed the snow cover dynamics in nine Alpine Italian catchments using long time series of satellite-derived snow line elevation (SLE) measurements. We compared the SLE of the hydrological year 2021/22 to the long-term dynamics of 1985-2021. In early 2022, the SLE was located several hundred meters above the expected median values in all of the nine catchments. The resulting lack of snow cover was more pronounced in the Western Alps than in the Eastern Alps. Although snow cover data from optical satellite imagery does not contain information about snow depth and water content, the derived SLE dynamics show good agreement with the Standardised Snowpack Index (SSPI), which is based on the snow water equivalent (SWE). While the exact relationships between SLE, SWE and runoff have to be explored further on the catchment basis, long-time series of SLE show the potential for use in drought early warning systems.
DOI: 10.3390/rs14236091
