The joint occurrence of extreme temperature and precipitation patterns associated with the synoptic systems activity over the Mediterranean
Abstract
The synoptic weather systems are often related with high impact phenomena; from cold-spells and floods to prolonged droughts and heatwaves, and, thus, they can significantly affect fauna and flora, public health or human infrastructure. Here, we study the association of the synoptic activity with the joint occurrence of extreme temperature and precipitation over the Mediterranean, which can reflect extreme conditions better than temperature or precipitation statistics considered separately (Beniston, 2009).
The joint modes of temperature and precipitation extremes are represented by four combined extreme indices, concerning the co-occurrence of Cold/Dry days (CD), Cold/Wet days (CW), Warm/Dry days (WD), Warm/Wet days (WW). They count the number of days over a period (here seasons) having at the same time: i) temperature below the 25th (Cold day) or above the 75th (Warm day) percentile of the mean temperature and ii) precipitation below the 25th (Dry day) or above the 75th (Wet day) percentile of mean daily precipitation amounts over a reference period (here 1981-2010). The respective daily data are derived from the high resolution gridded E-OBS datasets (0.25°x0.25°; v.17) from 1950 to 2017 (Haylock et al., 2008) that are based on the European Climate Assessment & Dataset information (ECA&D, Klein Tank et al., 2002). The synoptic system activity, which maxima exhibit significant spatial and temporal variability around the Mediterranean, is determined by the density and the depth of the cyclonic and anticyclonic systems, respectively. These properties of the synoptic activity have resulted from the comprehensive climatology of Mediterranean cyclones and anticyclones assembled using the cyclone finding and tracking algorithm of the University of Melbourne (Murray and Simmonds, 1991), based on the ECMWF ERA-Interim mean sea-level pressure fields for 1979-2017 (Dee et al., 2011). The co-examination of the temporal (seasonal and inter-annual) and spatial variations of the CD, CW, WD, WW indices along with the shifts of the cyclonic and anticyclonic activity, point out the particularity of the different regions of the Mediterranean, which can be attributed to the effects of its complex topography and to the role of the large-scale conditions that determine to a great extent the synoptic activity.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC21E1163H
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 1620 Climate dynamics;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 4313 Extreme events;
- NATURAL HAZARDS