ACCORD: Atmospheric circulation, classification and regional downscaling

• Forschungsstelle: EU FRP
• Projektnummer: 97.0084
• Projekttitel Englisch: ACCORD: Atmospheric circulation, classification and regional downscaling

Schlüsselwörter (Englisch)

Atmospheric circulation patterns; automated schemes; climate variability; NAO; downscaling; surface weather variables; precipitation.

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Coordinator: University of East Anglia (UK); 07 (U.BERN) , Assoc. Contractor der UEA-Norwich (UK)

Abstract (Englisch)

One of the reasons for the current high interest in climate variability is the likelihood of a growing anthropogenic influence. It's magnitude and timescale are such that it's detection demands a characterisation of climate variability over as long a period as possible. Europe is becoming one of the key areas of focus for investigations into climate variability because the North Atlantic is now recognised as being amongst the most important areas for ocean/atmosphere coupling, with climate manifestations - through the North Atlantic Oscillation (NAO) on the decadal timescale. Major modelling studies are underway or are planned. There are also studies to further explore seasonal predictive capabilities from sea-surface temperatures. Both types of study require a much better characterisation of the variability of climate in the North Atlantic/Europe sector than is currently available.
Much effort is also expended on GCM (and higher resolution) simulations of present climate and the projection of future climates. Across Europe, impact studies are dependent on climate scenarios generated by 'downscaling' from such models. The assumptions upon which such scenarios are based - that the model control runs adequately simulate present climate and are internally consistent, and that the relationships between large-scale and local climate are stationary over time - are too rarely tested at the regional and sub-regional scales. A prime reason for the inadequate testing of these assumptions is the current absence of robust, automated methodologies for classifying circulation patterns.
ACCORD addressed the essential requirements and current shortcomings highlighted above. It undertook a comprehensive assessment of existing methods of circulation classification, and developed emerging techniques to produce automated schemes, taking into account space-scales, transportability, powers of discrimination and robustness. Primary information was the surface pressure from 1881, but upper-air (reanalysis) data were also used. ACCORD also examined whether clustering of surface weather variables provided more discriminating power than spatial recognition schemes for pressure.
ACCORD characterised North Atlantic and European circulation variability over 115 years; this work ranged across time- and space-scales, analysed circulation modes, synoptic and subsynoptic features and characteristics, and included blocking, cut-off lows, Mediterranean and lee cyclones, and thunderstorms and precipitation types.
One of ACCORD's main aims was the identification of the importance of the NAO - the most important controlling circulation characteristic for Europe - for seasonal, annual and multiannual distributions of temperature and precipitation. The recent increases in precipitation over many areas of northwest Europe were examined for links both with large-scale and sub-regional circulations. The adopted automated circulation schemes were used to better discriminate observed surface variables (improved downscaling) in European sub-regions.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0084