Climate ‘memory’ may aid long range forecasts

Researchers at Harper Adams University College, Shropshire, believe a ‘memory’ in the climate system could be tapped to improve long-range weather forecasts.

In the April edition of ‘Weather,’ the journal of the Royal Meteorological Society, an article co-written by Dr Peter Kettlewell will show how summer rainfall levels in the UK are affected by ‘remembered’ changes in winter air pressure over the North Atlantic ocean. The article is based upon the work of a team headed by Dr Kettlewell, a senior researcher at Harper Adams, and co-author Dr David Stephenson, Head of the Climate Analysis Group at the University of Reading. Sponsored by the Home Grown Cereals Authority (HGCA), this work has previously shown that the quality of UK wheat grain is directly affected by the climate changes over the North Atlantic Ocean. Large-scale alterations in air pressure between the northern and southern regions of the North Atlantic, known as the North Atlantic Oscillation or NAO, take place during the winter and affect the quality of wheat grain that is harvested during the following summer.

Continuing work on the phenomenon has now shown that the winter NAO affects wheat quality by influencing summer rainfall levels. High NAO levels in winter tend to be followed by a dry summer in England and Wales, while wet summers tend to be preceded by low NAO winters. This relationship holds true for much of northwestern Europe and southern Scandinavia and has allowed Dr Kettlewell to build up a two category forecasting system, of above or below average summer rainfall.