Redefining the climate regions of Romania through objective methods

The south-eastern part of the European continent is known as a region where the types of climate are hard to be delimited, being indicated by Trewartha since 1961 among the so-called Earth's Climate Problem regions of the world. This is given especially by its position at the merges of arid and cold climate of the temperate zone in Europe. Taking to account this aspect, it is not surprisingly that after almost 100 years of climate classification attempts, there is still no agreement regarding the climate type of Romania and its corresponding subdivisions. Even if a weak majority of the Romanian climatologists plead for a temperate continental climate, some others consider that Romania has a typically temperate transitional climate specific for central Europe. However, most of previous regionalizations are highly subjective with no proper quantitative assessment of climate conditions. 

In our study a climate regionalization of Romania’s territory is proposed, based on an objective approach. For this purpose, 9 monthly climate parameters extracted from interpolation gridded data sets (ERA-5 land and ROCADA) were used.

The regionalization was performed by mixing two objective methods. Firstly, all the 108 input variables were reduced at 8 major factors using factor analysis. Secondly, those factors were used in a k-means clustering method and a new scheme of climate regionalization of Romanian territory was obtained. Through this, we succeed to delimitate 8 different climate subtypes within Romania's territory which we aggregated firstly in 2 major zonal climate types: (i) temperate transitional climate (TTC) from maritime to continental type, extended in the north-east part of Romania and (ii) temperate orographically sheltered climate (TOSC) with 2 major subtypes. The first sub-type of TOSC is extended within the Carpathian mountain arch (an extension of pannonian climate) and the second one covers the romanian part of the region between Carpathian and Balkan Mountain (lower danubian climate). Besides these two zonal types the major landforms of Romania impose specific climate conditions: (iii) the Carpathian mountains and sub-mountains area have their own climate features (CMSC) with 3 climate subtypes (precarpathian, eastern Carpathian and alpine climates), while the (iv) Black Sea shapes the main climate conditions of the south-eastern side of the country especially along the coast with 2 climate subtypes (ponto-deltaic and western pontic type). The main features of these climate types/subtypes are presented in detailed in the study.

In the meantime, the proposed climate regionalization covers partially the neighbor countries in an attempt to homogenize the different national perspectives on the climate types along the states boundaries in central and south-eastern Europe.