A new index for climate change evaluation - An example with the ALADIN and RegCM regional models for the Balkans and the Apennines

A new index for climate change assessment has been introduced. It is a ratio between the number of cases from a future period and the cases of a control experiment (reference period) falling within a predefined interval of the reference period. By "case" we mean the value of a meteorological element that meets certain conditions. Additionally, its conservation is a necessary condition for reducing the risk of losing a reliable signal of the modeled variability of future climate when applying bias correction methods (BCM's). The spatial distribution of this index is presented by using two regional climate models, ALADIN and RegCM4, over an area including the Balkan and Apennine Peninsulas. The assessment is performed for the average monthly temperature and precipitation. Both models have similar indices in broad areas. In winter, spring, and summer this refers to temperature and in spring and summer to rainfall.