Specific climate classification for Mediterranean hydrology and future evolution under Med-CORDEX regional climate model scenarios

Abstract

Abstract. The Mediterranean region is one of the most sensitive regions to anthropogenic and climatic changes, mostly affecting its water resources and related practices. With multiple studies raising serious concerns about climate shifts and aridity expansion in the region, this one aims to establish a new high-resolution classification for hydrology purposes based on Mediterranean-specific climate indices. This classification is useful in following up on hydrological (water resource management, floods, droughts, etc.) and ecohydrological applications such as Mediterranean agriculture. Olive cultivation is the characteristic agricultural practice of the Mediterranean region. The proposed approach includes the use of classic climatic indices and the definition of new climatic indices, mainly precipitation seasonality index Is or evapotranspiration threshold SPET, both in line with river flow regimes, a principal component analysis to reduce the number of indices, K-means classification to distribute them into classes, and finally the construction of a decision tree based on the distances to class kernels to reproduce the classification without having to repeat the whole process. The classification was set and validated by WorldClim-2 at 1 km high-resolution gridded data for the 1970–2000 baseline period and 144 stations' data over 30 to 120 years, both at monthly time steps. Climatic classes coincided with a geographical distribution in the Mediterranean ranging from the most seasonal and driest class 1 in the south to the least seasonal and most humid class 5 in the north, showing the climatic continuity from one place to another and enhancing the visibility of change trends. The MED-CORDEX ALADIN and CCLM historical and projected data at 12 and 50 km resolution simulated under the RCP4.5 and 8.5 scenarios for the 2070–2100 period served to assess the climate change impact on this classification by superimposing the projected changes on the baseline grid-based classification. RCP scenarios increase the seasonality index Is by +80 % and the aridity index IArid by +60 % in the north and IArid by +10 % without Is change in the south, hence causing the wet season shortening and river regime modification with the migration north of moderate and extreme winter regimes instead of early spring regimes. The ALADIN and CCLM regional climate models (RCMs) have demonstrated an evolution of the Mediterranean region towards arid climate. The classes located to the north are slowly evolving towards moderate coastal classes, which might affect hydrologic regimes due to shorter humid seasons and earlier snowmelts. These scenarios might look favourable for Mediterranean cultivation; however, the expected impact on water resources and flow regimes will surely expand and directly hit ecosystems, food, health, and tourism, as risk is interconnected between domains. This kind of classification might be reproduced at the global scale, using the same or other climatic indices specific to each region, highlighting their physiographic characteristics and hydrological responses.

Assessment of future climate change impact on rainfed wheat yield in the semi-arid Eastern High Plain of Algeria using a crop model

“…4c, d). Allam et al (2020) found that increase in the mean temperature in the South Mediterranean including Algeria by 2070-2100 had a lower rate during winter and a higher rate during summer under RCP 4.5. Their findings disagree with that for the S2 scenario at both sites because increase in Tms is lower in summer and higher in winter in this study (Fig.…”

Optimal industrial localization by using geographic information systems in the Nador province (northeast of Morocco)

“…It is bordered to the north by the Mediterranean Sea, to the south by the provinces of Guercif and Taourirt, to the northwest by the province of Driouch and to the southeast by the province of Berkane. The province has a Mediterranean climate [13]. The geographical location of industrial companies is linked to the productivity and competitiveness of industries, as well as to the attractiveness of land These aspects of habitat [14], its nature and its factors are widely studied in the geography of the economy, A series of management problems on the ground result from industrial dynamism through the form and nature of the internal relationships that structure economic conditions on the ground from the geographical area in which they are endemic.…”

Impact of ocean-atmosphere coupling on present and future Köppen-Geiger climate classification in Europe

“…For an assessment of the applications of RCMs over Europe see e.g., the perspective of EURO-CORDEX (Jacob et al, 2020). High spatial resolution regional models are also important for other regions of the world, see for example the different results of the Coordinated Regional Climate Downscaling Experiment (CORDEX) initiative in (Allam et al, 2020;Cabos et al, 2019;Giorgi and Gutowski, 2015;Giorgi et al, 2021).…”

“…Climate classifications are algorithms that group locations with climate similarities into classes, each class being defined as a climate type (Jacobeit, 2010). The climate types for a certain classification are usually mapped to some other characteristic shared by the locations in each class, e.g., vegetation type, solar radiation, water availability (Allam et al, 2020), thermal comfort (Wan et al, 2010), suitability for a certain crop (Tonietto and Carbonneau, 2004), biodiversity (Metzger et al, 2013), habitat distribution (Guisan and Zimmermann, 2000), paleoclimate analyses (Willmes et al, 2017) or climate change (Belda et al, 2016) among others. The selection of an appropriate climate classification depends on the question being tackled.…”

“…Previous works have demonstrated the importance of high spatial resolution for climate classification in areas with a complex orography and also to improve the simulation of the atmosphere and ocean circulation, see e.g., the applications of Skalák et al (2018) for Central Europe climate change analysis, Andrade and Contente (2020) for the Iberian Peninsula, Barredo et al (2020) for European Alpine Tundra and Allam et al (2020) for Mediterranean hydrology analyses. The main objectives of this work are (i) to examine the sensitivity of present-time K-G climate types distribution in Europe to air-sea coupling processes and (ii) to understand how these processes affect the distribution of K-G types over Europe by the end of the 21st century assuming the Representative Concentration Pathway 8.5 (RCP8.5) scenario of the Coupled Model Intercomparison Project 5 (CMIP5).…”