Decadal changes in extreme daily precipitation in Greece (original) (raw)

Climate Change Impacts on Extreme Precipitation in Greek Areas

2015

In the current paper the effects of climate change on precipitation extremes in Greece are studied. The projections of RegCM3_10 climatic model in particular are evaluated, for a time period of 150 years (1951-2100) in four regions of Greece. The available precipitation data is separated in three parts of equal size (fifty years each), in order to represent the fifty years of the current, the short-term and the long-term future climate. Model precipitation data is found to hold bias, commonly detected in regional climate models, making it necessary to perform various methods of bias correction. Both parametric and non-parametric methods are used for all four regions analysed, selecting the most appropriate for each region. Extreme value theory (EVT) is then implemented for the bias corrected precipitation datasets and both GEV (Generalized Extreme Value Distribution) and GPD (Generalized Pareto Distribution) are fitted. For the GPD, declustering of the excesses over the selected thr...

Unravelling Precipitation Trends in Greece since 1950s Using ERA5 Climate Reanalysis Data

Climate

Precipitation is one of the most variable climatic parameters, as it is determined by many physical processes. The spatiotemporal characteristics of precipitation have been significantly affected by climate change during the past decades. Analysis of precipitation trends is challenging, especially in regions such as Greece, which is characterized by complex topography and includes several ungauged areas. With this study, we aim to shed new light on the climatic characteristics and inter-annual trends of precipitation over Greece. For this purpose, we used ERA5 monthly precipitation data from 1950 to 2020 to estimate annual Theil–Sen trends and Mann–Kendall significance over Greece and surrounding areas. Additionally, in order to analyze and model the nonlinear relationships of monthly precipitation time series, we used generalized additive models (GAMs). The results indicated significant declining inter-annual trends of areal precipitation over the study area. Declining trends were ...

Spatial variability and trends of the rain intensity over Greece

In this study, the spatial and temporal variability of the mean annual rain intensity in Greece are examined during a 41-year period (1962–2002). The meteorological datasets concern monthly rain amounts (mm) and the respective monthly durations (h) recorded at thirty two meteorological stations of the Hellenic National Meteorological Service, which are uniformly distributed on Greek territory, in order to calculate the mean monthly rain intensity. All the rain time series used in the analysis were tested by the application of the shortcut Bartlett test of homogeneity. The spatial distribution of the mean annual rain intensity is studied using the Kriging interpolation method, while the temporal variability, concerning the mean annual rain intensity trends along with their significance (Mann-Kendall test), is analysed. The findings of the analysis show that statistically significant negative trends (95% confidence level) appear mainly in the west sub-regions of Greece, while statistically significant positive trends (95% confidence level) appear in the wider area of Athens and the complex of Cyclades Islands. Further analysis concerning the seasonal rain intensity is needed, because there are different seasonal patterns, taking into account that, convective rain in Greece occurs mainly within the summer season.

Temporal and spatial variability of rainfall over Greece

Recent studies have showed that there is a significant decrease in rainfall over Greece during the last half of the pervious century, following an overall decrease of the precipitation at the eastern Mediterranean. However, during the last decade an increase in rainfall was observed in most regions of the country, contrary to the general circulation climate models forecasts. An updated high-resolution dataset of monthly sums and annual daily maxima records derived from 136 stations during the period 1940 – 2012 allowed us to present some new evidence for the observed change and its statistical significance. The statistical framework used to determine the significance of the slopes in annual rain was not limited to the time independency assumption (Mann-Kendall test), but we also investigated the effect of short-and long-term persistence through Monte Carlo simulation. Our findings show that (a) change occurs in different scales; most regions show a decline since 1950, an increase since 1980 and remain stable during the last 15 years, (b) the significance of the observed decline is highly dependent to the statistical assumptions used; there are indications that the Mann-Kendall test may be the least suitable method and (c) change in time is strongly linked with the change in space; for scales below 40 years relatively close regions may develop even opposite trends, while in larger scales change is more uniform.

ANALYSIS OF THE LONG-TERM PRECIPITATION SERIES AT ATHENS, GREECE

In this paper, the characteristics of the long-term precipitation series at Athens (1858-1985) have been statistically analyzed. This study covers both the history and the analysis of the data. The ten-year mean amounts, the monthly and annual amounts averaged over the intervals 1858-1890, 1891-1985, 1951-1980, 1858-1985, the mean number of hours of precipitation and the precipitation intensity are given. The analysis of long-term time series of climatic data (in particular precipitation) is a useful tool for the study of past climate. Different statistical techniques are used in order to depict monthly, seasonal and annual variations, as well as trends, periodicities and recurrence intervals of the amount, intensity and number of precipitation days. The analysis reveals many interesting characteristics. These characteristics of the precipitation regime are extended to a time scale from seasonal variation to a semi-secular trend. The study of such long-term series may be helpful not only in practical applications of rainfall, but also for explaining the possible physical or anthro-pogenic mechanisms of chmatxc fluctuations and tendencies. The series of precipitation at Athens is one of the longest in southeastern Europe.