Centennial Trends in Precipitation, Air Temperature, Evapotranspiration and Water Balance over Romania from Observational Data (1924–2023)

While climate variability in Romania since 1961 is well documented, studies spanning on longer periods are few, and use either modelled, or sparse observational data. This paper presents the 100-year trends in precipitation, air temperature (average, minimum and maximum), monthly air temperature range, potential evapotranspiration and water balance over Romania using data from 156 weather stations. The recently released, freely available RoCliHom dataset has been used for this purpose. Trend analysis was conducted with the nonparametric Mann-Kendall test, as it allows a direct comparison with the vast majority of previous studies on climatic changes in Romania. Our results indicate that, since 1924, air temperature had increased over the entire country in all months except autumn, showing that the warming signal has been consistent over the 100-year period. In contrast, annual precipitation amount looks stable at most stations, while 28% show increasing trends. Monthly temperature range had mostly decreased. Potential evapotranspiration has increased in winter, spring and especially in summer, when all stations present upward trends. Water balance had declined in August at almost half of the stations. Generally, the patterns of change are clear, without mixed trends (i.e., trends showing opposite signs for the same variable). Trend magnitudes of annual precipitation and air temperature are strongly correlated (p-value 0.001) with elevation.