Spatial coherence of meteorological droughts in the UK since 1914

We apply the drought severity index (DSI) on a multi-temporal basis to a monthly precipitation dataset to study the spatial coherence of meteorological droughts in the UK since 1914. Analyses are undertaken for the wet (OctoberMarch) and dry (AprilSeptember) seasons and for moderate and extreme drought severities. We develop a drought covariance index that allows us to quantify the spatial coherence of droughts based on the fraction of years with extreme (or moderate) droughts that each pair of grid points has in common. Results show greater coherence in (and more widespread) moderate, short duration and wet season droughts. Results are discussed in terms of the relationship between the North Atlantic Oscillation and precipitation, the spatial variability of precipitation and the detectability of droughts. Finally, we examine the implications of our study for drought management with a focus on water transfers.