Specification and prediction of monthly and seasonal rainfall over the south-west peninsula of England

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Abstract

An assessment of the extent to which atmospheric variables add to the specification and predictability of rainfall over the south-west peninsula of England (SWPE), as provided by North Atlantic sea surface temperatures (SSTs), is undertaken. To this end multivariate specification and prediction models are developed, describing rainfall variations over the SWPE at monthly and seasonal time-scales. Results reveal that synchronous variations in atmospheric circulation characteristics are the main specifiers of monthly and seasonal rainfall variability, chiefly mean monthly sea-level pressure, vorticity and atmospheric water vapour flux. In contrast, the predictability of rainfall for one- and two-months, and one- and two-seasons ahead is more dependent on SST than atmospheric circulation variability. Both the tropical Atlantic and the Greenland–Iceland (Norwegian Sea) regions of the North Atlantic appear important as centres of action in terms of SST–SWPE rainfall links. Although SSTs account for the majority of variance in monthly and seasonal rainfall, a moderate improvement of rainfall prediction is achieved with the inclusion of atmospheric water vapour flux in prediction models for one-month to two-seasons ahead, as it acts as an atmospheric bridge between the ocean and land in terms of precipitation delivery. The empirical relationships revealed between SWPE rainfall, and atmospheric and SST variability are discussed in terms of the main components of the North Atlantic climate system. Copyright © 2004 Royal Meteorological Society

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