Studying the process of climate change using the continuous form of the Feddema climate classification

An important field of application of climate classifications is the study of climate change. Feddema’s climate classification scheme, which is a simplified water-budget based Thornthwaite-type method set out to better define climate parameters to interpret climate change processes for both research and educational purposes. However, pre-defined classes can limit the analysis. For example, grid points with values of the variables required for climate classification close to the climate boundaries can switch to a value belonging to another climate type interval without significant change in the climate variables, and similarly, a significant change is not necessarily will change the category. Feddema's method is suitable not only for determining the direction and extent of expected shifts in the climate and seasonality type changes, but also through the shift of indices expressing annual and seasonal characteristics: annual heat and water availability, seasonal variability, and the seasonally changing variable.

In this study, projected annual and seasonal changes of the Larger Carpathian Region (LCR)'s climate during the 21^st century are analysed based on the Feddema-continuous approach. Observational data are taken from the CarpatClim which is the best open access dataset for the region. Projected changes are estimated using an RCA4-EC-EARTH simulation with EUR-11 resolution, following the RCP8.5 scenario from EURO-CORDEX.  According to the results, the Feddema-continuous method allows to show the magnitude and direction of changes of an area classified in a specific climate or seasonality type based on the Feddema-indices determined per grid point. Moreover, it is also presented how the newly occurred warm thermal-category developed according to the changes in the water-budget. The method also allows to determine the trajectory of changes in different climate characteristics during the 21^st century.