Initial Spatio-Temporal Assessment of Aridity Dynamics in North Macedonia (1991–2020)

Aridity represents a fundamental climatic constraint governing water resources, eco-system functioning, and agricultural systems in transitional climate zones. This study examines the spatial organization and temporal variability of aridity and thermal con-tinentality in North Macedonia using observational records from 13 meteorological stations distributed across contrasting altitudinal and physiographic settings. The analysis is based on homogenized monthly and annual air temperature and precipitation series covering the period 1991–2020. Aridity and continentality were quantified using the De Martonne Aridity Index (IDM), the Pinna Combinative Index (IP), and the Johansson Continentality Index (JCI). Temporal consistency and trend behavior were evaluated using Pettitt’s nonparametric change-point test, linear regression, the Mann–Kendall test, and Sen’s slope estimator. Links between aridity variability and large-scale atmospheric circulation were examined using correlations with the North Atlantic Oscillation (NAO) and the Southern Oscillation Index (SOI). The results show a spatially consistent and statistically significant increase in mean annual air temper-ature, with a common change point around 2006, while precipitation displays strong spatial variability and limited temporal coherence. Aridity patterns display a strong altitudinal control, with extremely humid to very humid conditions prevailing in mountainous western regions and semi-humid to semi-dry conditions dominating lowland and southeastern areas, particularly during summer. Trend analyses do not reveal statistically significant long-term changes in aridity or continentality over the study period, although low-elevation stations exhibit weak drying tendencies. A mod-erate positive association between IDM and IP (r = 0.66) confirms internal consistency among aridity indices, while summer aridity shows a statistically significant relationship with the NAO. These results provide a robust climatic reference for North Mace-donia, establishing a first climatological baseline of aridity conditions based on multi-ple indices applied to homogenized observations, and contributing to regional assess-ments of hydroclimatic variability relevant to climate adaptation planning.