North Atlantic sea surface temperature, atmospheric circulation and summer drought in Great Britain

Improved understanding of climate system variation that leads to the development of streamflow drought will improve prospects of forecasting drought occurrence, and also inform drought mitigation and adaptation strategies. This research need is addressed here through investigation of the chain of processes linking concurrent and antecedent ocean-atmosphere variation to summer drought occurrence in four British drought regions. Results reveal that in some regions, drought development is associated with a horseshoe pattern of North Atlantic sea surface temperature (SST) anomalies that are most apparent in the six months preceding drought onset. This horseshoe pattern is similar to the pattern of SST anomalies associated with the North Atlantic Oscillation (NAO). However, analyses of geopotential height fields prior to drought onset reveal ocean-atmosphere forcing of drought events to be more complex than can be described simply by correlation of NAO and drought indices.