Drought Variability and Trend Over the Lombardy Plain from Meteorological Station Records
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The spatial and temporal variability of droughts over the period 1951–2017 for a portion of Lombardy plain (Northern Italy) was reconstructed starting from a quality-checked and homogenized database of long precipitation and temperature station records covering the study region. The monthly meteorological series were interpolated over the period 1951–2017 onto a 30-arc second resolution grid covering the area by means of an anomaly-based procedure and the gridded fields were used to extract for each cell the series of two standardized drought indices: Standardized Precipitation Index (SPI) and Standardized Precipitation-Evapotranspiration Index (SPEI). SPI and SPEI trend analyses were performed on annual and seasonal scales at both regional and grid-point levels. Theil-Sen test on SPI values highlighted a significant drying tendency (Mann-Kendall p-value <0.05) for summer only (−0.14 decade−1), while SPEI series exhibited a more negative summer trend (−0.22 decade−1) and significant reductions also in spring and annual values (−0.14 and −0.17 decade−1, respectively), suggesting an increase of evapotranspiration rates driven by higher temperature. Moreover, the trend analyses at grid cell level highlighted a greater negative and significant tendency for the western and southern part of the domain. Similar outcomes were obtained by assessing the temporal evolution of drought features over the decades in terms of frequency, duration and severity.
KeywordsDrought SPI SPEI Trend analysis Observations
The activity presented in the paper is part of the research grant “SO-WATCH—SOft path WATer management adaptation to CHanging climate”, funded by Fondazione CARIPLO (www.fondazionecariplo.it).
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