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The assessment of future precipitation variations prevailing in an area is essential for the research regarding climate and climate change. The current paper focuses on 3 selected areas in Greece that present different climatic characteristics due to their location and aims to assess and compare the future variation of annual and seasonal precipitation. Future precipitation data from the ENSEMBLES anthropogenic climate-change (ACC) global simulations and the Climate version of the Local Model (CLM) were obtained and analyzed. The climate simulations were performed for the future periods 2021–2050 and 2071–2100 under the A1B and B1 scenarios. Mann–Kendall test was applied to investigate possible trends. Spatial distribution of precipitation was performed using a combination of dynamic and statistical downscaling techniques and Kriging method within ArcGIS 10.2.1. The results indicated that for both scenarios, reference periods and study areas, precipitation is expected to be critically decreased. Additionally, Mann–Kendall test application showed a strong downward trend for every study area. Furthermore, the decrease in precipitation for the Ardas River basin characterized by the continental climate will be tempered, while in the Sperchios River basin it will be smoother due to the influence of some minor climatic variations in the basins' springs in the highlands where milder conditions occur. Precipitation decrease in the Geropotamos River basin which is characterized by Mediterranean climate will be more vigorous. B1 scenario appeared more optimistic for the Ardas and Sperchios River basins, while in the Geropotamos River basin, both applied scenarios brought similar results, in terms of future precipitation response. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this paper is to study the spatial and temporal variability of the Aridity Index (AI) in Greece, per decade, during the 50-year period (1951–2000). Besides, the projected changes in ensemble mean AI between the period 1961–1990 (reference period) and the periods 2021–2050 (near future) and 2071–2100 (far future) along with the inter-model standard deviations were presented, based on the simulation results, derived from a number of Regional Climatic Models (RCMs), within the ENSEMBLE European Project. The projection of the future climate was done under SRES A1B. The climatic data used, concern monthly precipitation totals and air temperature from 28 meteorological stations (22 stations from the Hellenic National Meteorological Service and 6 stations from neighboring countries, taken from the Monthly Climatic Data for the World). The estimation of the AI was carried out based on the potential evapotranspiration (PET) defined by Thornthwaite (1948). The data processing was done by the application of the statistical package R-project and the Geographical Information Systems (GIS). The results of the analysis showed that, within the examined period (1951–2000), a progressive shift from the “humid” class, which characterized the wider area of Greece, towards the “sub-humid” and “semi-arid” classes appeared in the eastern Crete Island, the Cyclades complex, the Evia and Attica, that is mainly the eastern Greece. The most significant change appears during the period 1991–2000. The future projections at the end of twentieth century, using ensemble mean simulations from 8 RCMs, show that drier conditions are expected to establish in regions of Greece (Attica, eastern continental Greece, Cyclades, Dodecanese, eastern Crete Island and northern Aegean). The inter-model standard deviation over these regions ranges from 0.02 to 0.05 against high values (0.09–0.15) illustrated in western mountainous continental Greece, during 2021–2050. Higher values of inter-model standard deviation appear in the 2071–2100 ranging from 0.02 to 0.10 reaching even 0.50 over mountainous regions of the country. [Copyright &y& Elsevier]

Abstract: Measurements of positive and negative small atmospheric ion concentrations have been made regularly since 1968 at the National Observatory of Athens (NOA). In this paper the 17-year period 1968–1984 is summarized. The diurnal and annual variations are examined, and Fourier analysis is also used for the study of the diurnal variation. The concentrations of small ions follow a double diurnal course. The maxima occur near 3–5 h and 13–16 h local time (LT=GMT+2 h). The minima are observed at 6–8 h and 21–23 h. The annual course of small ions presents maximum concentration values around the summer season. The mean of the small ion concentration (SIC) for the 17-year period (1968–1984) is n + =188.8 ions/cm3 for positive ions and n − =151.1 ions/cm3 for negative ions. Their ratio is equal to 1.25. The year-to-year variation of SIC for the examined period shows a negative trend. The results from multiple regression analysis show that wind speed and SIC are positively correlated, while relative humidity, smoke and sulphur dioxide are negatively correlated. [Copyright &y& Elsevier]

Tornadoes and waterspouts occur in various parts of Greece and may often reach the media as remarkable events, depending of their intensity and the level of damage. This paper is based on a research started from the beginning of 2000 for identifying and recording tornadoes and waterspouts in Greece and evaluating their intensity and other fundamental characteristics. Search of historical events for obtaining more comprehensive tornado climatology is in progress. In an almost 3-year period, January 2000–September 2002, tornadoes and waterspouts have been reported from various parts of Greece, including western Greece, the Ionian islands and western Peloponnese mainly during autumn and winter. Northern Greece is affected by tornadic activity mostly during summer and early autumn. The geographical distribution showed a preference for tornado occurrence mainly in coastal areas. Based on this almost 3-year data sample, a mean number of six tornadoes per year has resulted, corresponding to a density of 0.45 10−4 km−2 year−1. Maximum intensity of tornadoes recorded was rated as T6 of the Tornado and Storm Research Organization (TORRO) scale (F3 of the Fujita scale). A basic synoptic typing scheme is presented, including four synoptic circulation patterns associated to tornado occurrence. [Copyright &y& Elsevier]