The Palmer Drought Severity Index (PDSI) as an indicator of soil moisture

Detailed observation of soil moisture time series has of practical importance either in strategic preparing of researches or in professional planning. Meteorological-related spatial and temporal connections of soil moisture were investigated on monthly Palmer Drought Severity Index (PDSI) time series of five meteorological stations in Eastern Hungary (Miskolc, Nyı́regyháza, Debrecen, Kecskemét and Szeged) for the period 1901-1999. The calculated PDSI values were compared with the soil moisture content of the upper one meter soil layer. The measured soil moisture time series come from the authors ([Dunkel, Z., 1994; Lambert, K., et al., 1993 (in Hungarian)]). Both the used soil moisture time series and the Pálfai-index, expressing numerically daily hydrological extremes ([Pálfai, I.,1991]), confirmed our result independently of each other according to which PDSI is a good indicator of the soil moisture fluctuations in the upper one meter soil layer of the Great Hungarian Plain. On the basis of the regression coefficients of the linear connection, the index values can be expressed in physical unit of the water content in the upper one meter soil layer, as well. As a result of our examinations, the index has favourable statistical features; namely, the distribution of monthly samples is normal. Analysing spatial and temporal connections of the varied hydrometeorological relations of the selected region, average spatial and strong temporal correlations were established and these results are functions of intra-annual variability of precipitation.