Comment on nhess-2021-46

Abstract

In this study we analyze the drought features at European level over the period 1901 -2019, using three drought indices: the Standardized precipitation (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI) and the self-calibrated Palmer Drought Severity Index (scPDSI). The results based on the SPEI and scPDSI indices point out to the fact that central Europe (CEU) and the Mediterranean region (MED) are becoming dryer, due to an increase in the potential evapotranspiration and the mean air 15 temperature, while the northern part of Europe (NEU) is becoming wetter. By contrast, the SPI drought index does not reveal these changes in the drought variability, mainly due to the fact that the precipitation does not exhibit a significant change, especially over CEU. SPEI12 indicates a significant increase both in the frequency and area over the last three decades for MED and CEU, while SPI12 is not capturing these features. By analyzing the joint probability of compound events (e.g. high temperatures/droughts), 20 we show that the potential evapotranspiration and the mean air temperature are becoming essential components for drought occurrence over CEU and MED. This, together with the projected increase in the potential evapotranspiration under a warming climate, has significant implications concerning the future occurrence of drought events, especially for MED and CEU regions.