A drought climatology for Europe

Abstract

We present a high spatial resolution, multi‐temporal climatology for the incidence of 20th century European drought. The climatology provides, for a given location or region, the time series of drought strength, the number, the mean duration, and the maximum duration of droughts of a given intensity, and the trend in drought incidence. The drought climatology is based on monthly standardized precipitation indices (SPIs) calculated on a 0.5° grid over the European region 35–70 °N and 35 °E–10 °W at time scales of 3, 6, 9, 12, 18, and 24 months for the period 1901–99. The standardized property facilitates the quantitative comparison of drought incidence at different locations and over different time scales. The standardization procedure (probability transformation) has been tested rigorously assuming normal, log–normal, and gamma statistics for precipitation. Near equivalence is demonstrated between the Palmer drought severity index (PDSI) and SPIs on time scales of 9 to 12 months. The mean number and duration by grid cell of extreme European drought events (SPI ≤ −2) on a time scale of 12 months is 6 ± 2 months and 27 ± 8 months respectively. The mean maximum drought duration is 48 ± 17 months. Trends in SPI and PDSI values indicate that the proportion of Europe experiencing extreme and/or moderate drought conditions has changed insignificantly during the 20th century. We hope the climatology will provide a useful resource for assessing both the regional vulnerability to drought and the seasonal predictability of the phenomenon. Copyright © 2002 Royal Meteorological Society.