Objective Definition of Climatologically Homogeneous Areas in the Southern Balkans Based on the ERA5 Data Set

Christos J Lolis,Georgios Kotsias,Aristides Bartzokas

doi:10.3390/cli6040096

Abstract

An objective definition of climatologically homogeneous areas in the southern Balkans is attempted with the use of daily 0.25° × 0.25° ERA5 meteorological data of air temperature, dew point, zonal and meridional wind components, Convective Available Potential Energy, Convective Inhibition, and total cloud cover. The classification of the various grid points into climatologically homogeneous areas is carried out by applying Principal Component Analysis and K-means Cluster Analysis on the mean spatial anomaly patterns of the above parameters for the 10-year period of 2008 to 2017. According to the results, 12 climatologically homogenous areas are found. From these areas, eight are mainly over the sea and four are mainly over the land. The mean intra-annual variations of the spatial anomalies of the above parameters reveal the main climatic characteristics of these areas for the above period. These characteristics refer, for example, to how much warmer or cloudy the climate of a specific area is in a specific season relatively to the rest of the geographical domain. The continentality, the latitude, the altitude, the orientation, and the seasonal variability of the thermal and dynamic factors affecting the Mediterranean region are responsible for the climate characteristics of the 12 areas and the differences among them.

Highlights

The Mediterranean Sea is located in a transitional climatic area between Europe, Africa, and Asia and its climate is widely known as “the Mediterranean climate”
The southern Balkans is such a region and the present study aims at examining this variability by defining climatologically homogeneous subregions within it, i.e., subregions with characteristic seasonal variations of the main climatic parameters
The data used in the present study are daily (00UTC and 12UTC) 0.25◦ × 0.25◦ grid point values of air temperature (AT), dew point temperature (DP), zonal (ZW) and meridional (MW) wind components, Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), and total cloud cover (TCC) for the southern Balkans area (19◦ –29◦ E, 34◦ –42◦ N) (Figure 1) for the 10-year period of 2008 to 2017, obtained from the ERA5 Reanalysis data set [22]

Summary

Introduction

The Mediterranean Sea is located in a transitional climatic area between Europe, Africa, and Asia and its climate is widely known as “the Mediterranean climate”. [1,2,3,4,5] These seasonal variations appear over the whole Mediterranean region, they present significant differences among the various subregions. These differences are connected to various atmospheric and geographical factors. The position and the variability of the large-scale atmospheric circulation systems (e.g., the subtropical anticyclone of the North Atlantic and the south Asian summer low) and the global atmospheric oscillations affecting the region are dominant atmospheric circulation factors connected to the significant spatial variability of climate within the Mediterranean region [6,7,8].

Methods

Results

Discussion

Conclusion