Downloaded 09/25/21 07:57 AM UTC Earth Interactions D Volume 14 (2010) D Paper No

Earth Interactions d Volume 14 (2010) d Paper No. 5 d Page 1 Copyright Ó 2010, Paper 14-004; 46114 words, 7 Figures, 0 Animations, 0 Tables. http://EarthInteractions.org Storminess and Environmental Changes in the Mediterranean Central Area Nazzareno Diodato and Gianni Bellocchi* Met European Research Observatory, GEWEX-CEOP Network, World Climate Research Programme, Benevento, Italy Received 11 October 2009; accepted 7 April 2010 ABSTRACT: Earth ecosystems are not static, and they respond to environmental changes, particularly climatic and anthropogenic. Precipitation varying in its extremeness, with shifts to greater or lesser intensity of individual storms and/or to change in the length and frequency of wet and dry periods, can ad- versely affect both urban and rural ecosystems. Here, the authors review long- term precipitation records of the central Mediterranean area and employ a Web geographical information system (GIS)-based analytical approach to compare current rainfall impact with historical data on different spatial and temporal scales. Autumn (September–November) was recognized as the most hazardous season that marks the evidence of a changing climate, with a shift toward more intense rainfalls in recent times. In the first decade of the third millennium, areas of peninsular and insular Italy have been especially affected by extreme rains. A focus was put on the island of Sicily, where extraordinary rain events occurred in September 2009, discussed in the context of upcoming trends and climate histories. An improved knowledge and understanding of the scale at which changes on extremes occur is essential for dealing with the forthcoming challenges regarding soil and water conservation practices. The characteristics of changes in natural rainfall, its role on terrestrial ecosystems, and its effect on * Corresponding author address: G. Bellocchi, Met European Research Observatory, via Monte Pino, 82100 Benevento, Italy. E-mail address: [email protected] DOI: 10.1175/2010EI306.1 Unauthenticated | Downloaded 09/25/21 07:57 AM UTC Earth Interactions d Volume 14 (2010) d Paper No. 5 d Page 2 surface water erosion dynamics are discussed. It is argued that understanding these issues are major priorities for future research to promote a better understanding of the Earth interaction with water resources and related hydrological issues. KEYWORDS: Climate change; Extreme rainfall; Mediterranean central area 1. Introduction A march of waters; mustering from above, Ne` di rado dal ciel scende dirotto, D’acque il The clouds roll up the tempest, heaped and diluvio: in procelloso nembo; grim Vedi repente le aggruppate nubi, Fosche With angry showers: down falls the height addensarsi, e con opaco velo; of heaven, Tutto il mondo oscurar. Disciolto in acqua, And with a great rain floods the smiling Sembra cadere il ciel; scorre a crops, torrenti, La pioggia, e inonda i seminati, e Theoxen’slabour:nowthedikesfillfast, strugge Le fatiche de’ buoi: And the void river-beds swell thunderously, s’empion le fosse, Gonfiansi i fiumi, e And all the panting firths of Ocean boil. la sonante piena Cacciano al mar (...). Publio Virgilio Marone, Georgiche, Book I, written 29 BCE There is growing evidence at global, regional, and local scales that intra-annual precipitation regimes have already become more extreme (Easterling et al. 2000; Groisman et al. 2005; Knapp et al. 2008). However, the uncertainty of climate information poses challenges for the analysis of observed rain data because the heaviest areas of precipitation may fall between recording stations (Willmott and Legates 1991). For instance, assertions about extreme precipitation changes may be more reliable for regions with dense networks because of the small radius of correlation for many intense rainfall events (Groisman et al. 2005). Few literature sources are available worldwide regarding the extreme precipitation, especially about rainstorm effects on terrestrial ecosystems and water resources (e.g., Clarke and Rendell 2007; Curtis et al. 2007; Zolina et al. 2009). This also poses another question related to the development of dynamic hydrological models, which is hampered by incomplete understanding of spatially varying processes and the lack of adequate datasets to spatially characterize varying rain inputs. According to Wei et al. (Wei et al. 2009), secular records of historical precipitation data are required to deal with long-term studies and cross-site comparisons. This is especially so in the Mediterranean region, where human pressure and erratic rainfall patterns with marked interannual variability expose landforms to exacerbated, damaging hydrological processes (van Leeuwen and Sammons 2003; Sańchez et al. 2004; van Rompaey et al. 2005) and also to spur the emergence of new hazards, such as coastal and urban flooding (Papathoma and Dominey-Howes 2003; Barroca et al. 2006). Mediterranean storms and cyclones tend to be characterized by short life cycles, with average radius ranging from 300 to 500 km (after Lionello et al. 2006), many of which are a combination of both frontal and convective rainstorms. Heavy flooding and storms occurring at Mediterranean sites were found to be characterized by a complex property, known as multifractality, which is the spatial distribution organized into clusters of high rainfall localized cells embedded within a larger cloud system or clusters of lower intensity (Mazzarella 1999). Unauthenticated | Downloaded 09/25/21 07:57 AM UTC Earth Interactions d Volume 14 (2010) d Paper No. 5 d Page 3 Figure 1. (a) Economic losses from damaging hydrological events worldwide (from APFM) and (b) expected value of the expected cost as a function of different daily rainfall threshold values (Martina et al. 2006; modified). For the Holocene—the geological epoch started around 10 000 BCE and con- tinues to the present—there is continued debate about the relative impact of anthropogenic activity, but there is also increasing recognition that Mediterranean- type ecosystems should not be regarded as fragile, degraded landscapes but instead as disturbance-adapted systems (Allen 2003). Nevertheless, conservation measures face increasing challenges from contemporary human forcing and rainstorm events. The increase in sealed surfaces resulting from changes in land use together with a decrease in forest cover has increased the frequency and size of storm runoff too, causing flooding, mudflows, and landslides. These events may be grouped in some particularly rainy years or months according to storms climatic variability over interannual to century scales (Garcıá-Oliva et al. 1995; D’Odorico et al. 2001; Peterson et al. 2002; Cavazos and Rivas 2004). Rainfall variables such as depth, duration, and intensity (and its erosive power) are becoming more and more changeable (Diodato and Bellocchi 2009a) and with a regimen that would still markedly change over time and space in the following years (Richard 2007). The environmental and economic impact of these events can be high in several regions (Kunkel et al. 1999; Alcańtara-Ayala 2002), especially in agricultural and river-torrential areas (Thornes and Alcańtara-Ayala 1998; Camarasa Belmonte and Segura Beltrań 2001; Ramos and Mulligan 2003). The European southernmost regions are especially more sensitive to erratic rainfalls and are currently threat- ened by land degradation leading to a lowering in water resource availability and agricultural productivity (Poesen and Hooke 1997). Over the 1980–90 decade, for example, flash floods caused billions of euros of damage in Europe (Gruntfest and Handmer 2001). This is also evident with more recent data that show (Figure 1a) the extent to which economic losses from worldwide hydrological disasters tend to increase [World Meteorological Organization Advanced Programme on Flood Management (APFM); available online at http://www.apfm.info/index.htm]. In Figure 1b, one can see instead how the shape of expected-value cost of disasters affected by a given cumulated volume of rainfall during a storm event (i.e., 50 mm day21) separates decreasing cost from increasing cost. This is so because dry periods are associated with expected-value costs related to environmental drought Unauthenticated | Downloaded 09/25/21 07:57 AM UTC Earth Interactions d Volume 14 (2010) d Paper No. 5 d Page 4 stress, whereas excessive rains (wet periods) turn into expected-value costs associated with multiple damaging hydrological events. Threshold behavior manifests itself as an indicator of economic losses, and its characteristics are of importance for understanding and extrapolating the dynamics and stability of climate systems (Pitman and Stouffer 2006), the dynamics and resilience of geoecosystems, and the dynamics of fluxes in hydrologic systems (Zehe and Sivapalan 2009). Despite the general recognition that land degradation is a serious and widespread problem in Mediterranean countries, the same has not been quantified for many locations, and its geographical distribution and real extent are not accurately known, because pre- vailing studies only target subregional scales or isolated places (Clarke and Rendell 2007). There is a need to update and estimate the current overall hazard related to rainstorms and to assess in what measure hazardous rainstorms evolved with climate variability. The present work aims at prospecting, for the central Mediter- ranean and for multiple spatial and temporal scales, rain-intensity trends related to recorded extreme rainfalls. To achieve this goal, precipitation

Load more