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Dept. of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen,
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- PublicationRestrictedOn the internal variability of simulated daily precipitation(2015-05)
; ; ; ; ; ; ; ; ;Schindler, A.; MeteoSwiss ;Toreti, A.; JRC ;Zampieri, M.; CMCC ;Enrico, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Silvio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Fukutome, S.; MeteoSwiss ;Xoplaki, E.; Justus-Liebig University of Giessen ;Luterbacher, J.; Justus-Liebig University of Giessen; ; ; ; ; ; ; Climate model simulations are currently the main tool to provide information about possible future climates. Apart from scenario uncertainties and model error, internal variability is a major source of uncertainty, complicating predictions of future changes. Here, a suite of statistical tests is proposed to determine the shortest time window necessary to capture the internal precipitation variability in a stationary climate. The length of this shortest window thus expresses internal variability in terms of years. The method is applied globally to daily precipitation in a 200-yr preindustrial climate simulation with the CMCC-CM coupled general circulation model. The two-sample Cramér–von Mises test is used to assess differences in precipitation distribution, the Walker test accounts for multiple testing at grid cell level, and field significance is determined by calculating the Bejamini–Hochberg false-discovery rate. Results for the investigated simulation show that internal variability of daily precipitation is regionally and seasonally dependent and that regions requiring long time windows do not necessarily coincide with areas with large standard deviation. The estimated time scales are longer over sea than over land, in the tropics than in midlatitudes, and in the transitional seasons than in winter and summer. For many land grid cells, 30 seasons suffice to capture the internal variability of daily precipitation. There exist regions, however, where even 50 years do not suffice to sample the internal variability. The results show that diagnosing daily precipitation change at different times based on fixed global snapshots of one climate simulation might not be a robust detection method.110 18 - PublicationRestrictedAtlantic multi-decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summerWe analyze the influence of the Atlantic sea surface temperature multi-decadal variability on the day-by-day sequence of large-scale atmospheric circulation patterns (i.e. the “weather regimes”) over the Euro-Atlantic region. In particular, we examine of occurrence of weather regimes from 1871 to present. This analysis is conducted by applying a clustering technique on the daily mean sea level pressure field provided by the 20th Century Reanalysis project, which was successfully applied in other studies focused on the Atlantic Multi-decadal Oscillation (AMO). In spring and summer, results show significant changes in the frequencies of certain weather regimes associated with the phase shifts of the AMO. These changes are consistent with the seasonal surface pressure, precipitation, and temperature anomalies associated with the AMO shifts in Europe.
62 2 - PublicationOpen AccessProjections of global changes in precipitation extremes from CMIP5 models(2013)
; ; ; ; ; ; ; ; ; ;Toreti, A.; Dept. of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen, ;Naveau, P.; IPSL-CNRS ;Zampieri, M.; CMCC ;Schindler, A.; Dept. of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen, ;Scoccimarro, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Xoplaki, E.; Dept. of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen, ;Dijkstra, H. A.; Dept. of Physics and Astronomy, Utrecht University, Utrecht, The Netherlands. ;Gualdi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Luterbacher, J.; Dept. of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University of Giessen,; ; ; ; ; ; ; ; Precipitation extremes are expected to increase in a warming climate, thus it is essential to characterise their potential future changes. Here we evalu- ate eight high-resolution Global Climate Model simulations in the twenti- eth century and provide new evidence on projected global precipitation ex- tremes for the 21st century. A significant intensification of daily extremes for all seasons is projected for the mid and high latitudes of both hemispheres at the end of the present century. For the subtropics and tropics, the lack of reliable and consistent estimations found for both the historical and fu- ture simulations might be connected with model deficiencies in the repre- sentation of organised convective systems. Low inter-model variability and good agreement with high-resolution regional observations are found for the twentieth century winter over the Northern Hemisphere mid and high lat- itudes.245 404