Search results for "PRECIPITATION"

Carbonate precipitation in the alkaline lake Specchio di Venere (Pantelleria Island, Italy) and the possible role of microbial mats

2016

Abstract Alkaline lakes like the hydrothermally affected lake Specchio di Venere (Pantelleria Island, Central Mediterranean) are typical geological settings harbouring calcified microbial mats. The present work is focused on the discrimination between biotic and abiotic processes driving carbonate precipitation in this lake, using hydrochemical, mineralogical and isotopic data. Hydrochemical analyses demonstrate that the lake is nearly 10−fold supersaturated with regard to aragonite and seasonally reaches hydromagnesite supersaturation. Microscopic observations depict organosedimentary laminated structures consisting of microbial communities and aragonitic precipitates, which are rather dis…

2018

Abstract. The 4.2 ka BP event is defined as a phase of environmental stress characterized by severe and prolonged drought of global extent. The event is recorded from the North Atlantic through Europe to Asia and has led scientists to evoke a 300-year global mega-drought. For the Mediterranean and the Near East, this abrupt climate episode radically altered precipitation, with an estimated 30 %–50 % drop in rainfall in the eastern basin. While many studies have highlighted similar trends in the northern Mediterranean (from Spain to Turkey and the northern Levant), data from northern Africa and the central-southern Levant are more nuanced, suggesting a weaker imprint of this climate shift on…

Sensitivity of extreme rainfall to temperature in semi-arid Mediterranean regions

2019

Abstract Warmer air has the potential to hold more water vapour and, therefore, to provide more water to rainfall events. Studying the relationship between rainfall and temperature represents an emerging issue in hydrology and meteorology, since it can be considered fundamental for evaluating the effects of global warming on future precipitation. Various approaches have been tested across different parts of the world, in many cases observing an intensification of extreme precipitation at higher temperatures consistent with the well-known thermodynamic Clausius-Clapeyron relation (CC-scaling rate of 6–7%°C−1). However, at different locations for hourly time-scales, the temperature-extreme ra…

Multiple imputation of rainfall missing data in the Iberian Mediterranean context

2017

Abstract Given the increasing need for complete rainfall data networks, in recent years have been proposed diverse methods for filling gaps in observed precipitation series, progressively more advanced that traditional approaches to overcome the problem. The present study has consisted in validate 10 methods (6 linear, 2 non-linear and 2 hybrid) that allow multiple imputation, i.e., fill at the same time missing data of multiple incomplete series in a dense network of neighboring stations. These were applied for daily and monthly rainfall in two sectors in the Jucar River Basin Authority (east Iberian Peninsula), which is characterized by a high spatial irregularity and difficulty of rainfa…

Pre‐instrumental summer precipitation variability in northwestern Greece from a high‐elevation Pinus heldreichii network

2021

The spatiotemporal variability of precipitation is of vital importance to Mediterranean ecology and economy, but pre‐instrumental changes are not well understood. Here, we present a millennial‐length June–July precipitation reconstruction derived from a network of 22 Pinus heldreichii high‐elevation sites in the Pindus Mountains of northwestern Greece. Tree‐ring width chronologies from these sites cohere exceptionally well over the past several hundred years (r1467–2015 = 0.64) revealing coherence at inter‐annual to centennial timescales across the network. The network mean calibrates significantly against instrumental June–July precipitation over the past 40 years (r1976–2015 = 0.71), even…

Future Projection of precipitation changes in the Júcar and Segura River Basins (Iberian Peninsula) by CMIP5 GCMs Local Downscaling

2021

The basins of the Júcar and Segura rivers, on the Mediterranean coast of the Iberian Peninsula, present a special water problem and are of particular interest regarding climate change. These basins are very vulnerable to a possible scenario of decreasing water resources. Recent studies on historic rainfall since 1955 have indicated an ongoing loss of precipitation in their headwaters, especially in the case of the Júcar river. The aim of the present study is to perform climate projections for the precipitation variable for several future periods (2021–2040, 2051–2070, 2081–2100) and emission scenarios (RCPs 4.5, 8.5) within the Júcar and Segura River Basin authorities. For this purpose, a s…

Isotopic composition of single rain events in the central Mediterranean

2008

[1] The ratios of stable isotopes of single rain events were investigated during the period October 2005 to September 2006 in the central Mediterranean. Clear seasonal trends were identified in both oxygen isotope ratios and the deuterium-excess parameter, and these were ascribed to the dominant circulation systems during both cold and hot intraannual periods. Rain events were classified on the basis of the origin of rain-bearing systems. Air masses coming from the south usually give rise to rainwater with a low deuterium excess. Air masses coming from the north and the northeast are often dry and cold, and are associated with high evaporation from the Mediterranean Sea that occurs under is…

Isotopic composition of the precipitations in the central Mediterranean: Origin marks and orographic precipitation effects

2006

The isotopic composition of the rainfall in northwestern Sicily (Italy, central Mediterranean) was investigated in the period February 2002 to March 2003. A rain gauge network was installed and sampled monthly. The monthly values of the D and 18O ratios showed a wide range that reflected seasonal climatic variations. Mean weighted values were used to define an isotopic model of precipitation. Temporal variations in deuterium excess were also investigated. Using mean volume weighted values, the Local Meteoric Water Line (LMWL) can be represented by the equation: δD = 4.7δ18O - 8.2 (r2 = 0.96). Deuterium excess (d = δD - 8δ18O) was found to be strongly related to orography. The coastline samp…

Co-evolution of hydrological components under climate change scenarios in the Mediterranean area

2015

ABSTRACT The Mediterranean area is historically characterized by high human pressure on water resources. Today, while climate is projected to be modified in the future, through precipitation decrease and temperature increase, that jointly and non-linearly may affect runoff, concerns about water availability are increasing. For these reasons, quantitative assessment of future modifications in the mean annual water availability are important; likewise, the description of the future interannual variability of some hydrological components such as runoff and evapotranspiration are highly wished for water management and ecosystems dynamics analyses. This study investigates at basin spatial scale …

Climate of the Mediterranean

2012

This chapter considers a set of issues related to the synoptic climatology of the Mediterranean region (MR). The main Northern Hemisphere teleconnections affecting the MR and their role on temperature, precipitation, and atmospheric cyclones are described. The characteristics of the cyclones in the MR are presented. The role of teleconnections and atmospheric regimes on temperature and precipitation is discussed. The content includes extremes of temperature, precipitation, wind, and storminess (considering also marine aspects such as waves and storm surges).