The atmospheric drought and its spatial differentiation in Poland

The identification of dry events in Poland and the evaluation of the efficacy of various drought indices was conducted from April to September. Utilising meteorological data from 46 stations provided by the Polish Institute of Meteorology and Water Management National Research Institute, the study examined the Standardised Precipitation-Evapotranspiration Index (SPEI), the thermal-precipitation index (Ped index), and the Sielianinov index spanning from 1966 to 2020. The research primarily concentrated on detecting the frequency of dry months and verifying trends within these indices. Results indicate that drought conditions predominantly impact Central and Southwestern Poland, notably in April and the period from June to August. The frequency of atmospheric drought varied with each index: it exceeded 0.3 for the SPEI, ranged from over 0.2 to more than 0.5 for the Ped index, and surpassed 0.6 for the Sielianinov index. Trends depicted dryness with changes in drought indices surpassing 0.2 per decade. A comparative analysis of these indices revealed that the SPEI is most effective for detecting dry events, as evidenced by its consistent performance across meteorological and hydrological drought assessments. This study not only compares the application of different indices but also highlights regions more prone to atmospheric droughts. As a result, the regionalisation of drought risk in Poland was prepared according to the drought frequency and trends; therefore, three regions were extracted (Northern, Central and Southern Poland). The detection of meteorological dry events is crucial for predicting soil and hydrological droughts and assessing their detrimental effects on agriculture.