Effect of evapotranspiration parameterisation on the Palmer Drought Severity Index

The aim of the study is to compare two popular parameterisations of potential evapotranspiration, applied in computation of the Palmer Drought Severity Index. Among other differences, Thornthwaite method considers bare soil, whereas Blaney–Criddle method estimates evapotranspiration after specification of a given plant. Monthly PDSI series in the April–October growing season of maize are analysed at five stations in Eastern Hungary for the period 1901–1999. When using Blaney–Criddle method both the inter-annual and inter-monthly variability, i.e. standard deviation and auto-correlation decrease. Trends and regression coefficients to hemispheric temperature changes are smaller for latter parameterisation, as well. Synchronous correlation among the stations also decreases in this latter approach, whereas normality of the distribution remains valid in majority of months and stations.