CR 75:143-154 (2018)  -  DOI: https://doi.org/10.3354/cr01514

ABSTRACT: Changes in the reference evapotranspiration (ET₀) and precipitation (P) patterns in the Nemunas River basin (Baltic Sea catchment) are evident today and will be even more significant in the future. Nemunas basin aridity dynamics (1901-2010) and projections (2081-2100) were evaluated using the UNEP aridity index (AI). Historical analysis (CRU TS3.24.01) and future projections (EURO-CORDEX) of monthly air temperature and precipitation were used for the AI estimation. Projections of the meteorological parameters according to 4 Representative Concentration Pathway scenarios (RCP2.6, 4.5, 6.0 and 8.5) were used in the analysis. In the Nemunas River basin, evapotranspiration exceeded precipitation from April to August, and in a large part of the basin the climatic conditions during this part of the year could be described as dry subhumid (AI < 0.65). Since the 1980s, increased aridity has been observed between April and August due to a strong positive trend of ET₀ and a strong negative trend of P. Future projections (2081-2100) show that despite large uncertainties in the climate projections, it is more likely that the Nemunas basin climate will become more humid in April and May and drier between June and August. The increase in climate aridity during these months is more likely in the southern and central parts of the basin.

KEY WORDS: Nemunas basin · Reference evapotranspiration · Precipitation · Aridity index · AI · EURO-CORDEX · Climate change