Historical Climate Change in Sardinia (Italy): The dramatic runoff decrease in the last three decades and the effect of atmospheric circulation.
Abstract
In the last decades, climate change increased desertification process in Mediterranean regions, with dramatic consequences for agriculture and water availability. The position of the Sardinia island in the center of the western Mediterranean sea basin, its low urbanization and human activity and the interesting hydrologic database collected for the whole region from 1922 appoint Sardinia as a perfect reference laboratory for Mediterranean ecosystems studies and for investigating the impact of historical climate change on main hydrologic variables. Runoff data of 28 Sardinian basins are analyzed, showing a strong runoff decrease for all the basins in the last 40 years (hystorical trends are detected using the Mann Kendall test). Runoff decrease is mainly related to precipitation. We collect an innovative database of rainfall observations from 400 rain stations. The precipitation historical trend is still negative but the decrease is lower than the runoff decrease. This is because main runoff is in winter, which also plays a key role for the dam water supply, and winter precipitation shows a systematic stronger decrease. Interestingly, the decrease is more marked for the rain and discharge stations of the Sardinian west coast, which are exposed to the west European climate dynamics. In this sense, several studies have shown a significant correlation between the main meteorological variables and indices related to fluctuations in global scale, NAO (North Atlantic Oscillation) in Mediterranean regions, which controls the direction and strength of westerly winds and storm tracks into Europe. We found high negative correlations between NAO and precipitation and runoff during the winter season, and the correlations decrease with the increase of rain station longitudes. The results show a strong negative correlation at the stations of the Sardinian west coast, which is due to the exposure to the storm track dynamics. Instead a less negative correlation has been estimated for the east coast stations due to the impact of the orography which attenuate the large scale atmospheric dynamics, when storms cross Sardinian island from west to east. Hence, local effects - the mountain - can strongly impact and alter large scale atmosphere phenomena.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H33C1558M
- Keywords:
-
- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 1807 Climate impacts;
- HYDROLOGYDE: 1817 Extreme events;
- HYDROLOGYDE: 1833 Hydroclimatology;
- HYDROLOGY