Daily atmospheric circulation patterns for Catalonia (northeast Iberian Peninsula) using a modified version of Jenkinson and Collison method

Abstract The Western Mediterranean, in common with other subtropical regions, has certain characteristics that make a purely surface-based synoptic classification inadequate. Sometimes, despite the surface synoptic situation not being conducive to precipitation, a depression aloft can trigger convection and produce strong rains and flash floods. To account for this, we develop a new synoptic classification centred on Catalonia (north-east of the Iberian Peninsula) which combines upper air and surface pressure situations. The existing Jenkinson-Collison classification of the surface pressure field is combined with a new simplified upper air classification based on 500 hPa geopotential height. Despite a reduced number of types at 500 hPa, the combination of both surface and 500 hPa gives many potential combinations. A reduction in the overall number was achieved by adjusting the combined classification to replicate the manual classification of Martin-Vide. The final classification is reduced to 13 synoptic patterns each of which provides a clear and well-defined daily synoptic situation. It is used to characterize days with/without cold air pool (CAP) events, derived from a network of 50 temperature sensors distributed across Cerdanya in Eastern Pyrenees. We show our new classification to be better at discriminating strong CAP days from no-CAP days than classifications based on surface pressure alone. Thus there is potential for the classification to be used by forecasters as a first step for predicting temperature inversions and weather in the Eastern Pyrenees.