HR: 1020h
AN: PP52A-0648    [Abstracts]
TI: European Climate Patterns and their Variability 1766-2000
AU: * Casty, C
EM: casty@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern, 3012 Switzerland
AU: Wanner, H
EM: wanner@giub.unibe.ch
AF: Climatology and Meteorology, Institute of Geography, University of Bern, Hallerstrasse 12, Bern, 3012 Switzerland
AU: Wanner, H
EM: wanner@giub.unibe.ch
AF: NCCR Climate, University of Bern, Erlachstrasse 9a, Bern, 3012 Switzerland
AU: Luterbacher, J
EM: juerg@giub.unibe.ch
AF: Climatology and Meteorology, Institute of Geography, University of Bern, Hallerstrasse 12, Bern, 3012 Switzerland
AU: Luterbacher, J
EM: juerg@giub.unibe.ch
AF: NCCR Climate, University of Bern, Erlachstrasse 9a, Bern, 3012 Switzerland
AU: Stocker, T F
EM: stocker@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern, 3012 Switzerland
AU: Stocker, T F
EM: stocker@climate.unibe.ch
AF: NCCR Climate, University of Bern, Erlachstrasse 9a, Bern, 3012 Switzerland
AB: Independent climate field reconstructions covering Europe and the North Atlantic for the 500 hPa geopotential height field (Z500), land surface temperature (LST) and precipitation (LSP) are assessed regarding their main patterns of variability. We independently reconstructed monthly Z500, LST and LSP on a 2.5° grid for the North Atlantic/European region (30--80°N and 50W--40°E) using principal component regression for the period 1766 onwards. The reconstructions fully rely on early instrumental measurements. The reconstructions are independent in the sense that no common station data are used for the reconstruction of each parameter. The statistical models are fitted on the NCEP reanalysis (Z500) and CRU TS 2.1 for LST and LSP in order to receive 'paleoreanalyses' for the period prior to 1900.
Firstly, we investigate the evolution of LST and LSP since 1766 for each climatological season. Secondly, we comprise Z500, LST and LSP into a combined state vector. We then investigate the first few combined empirical orthogonal functions and principal components for each season. Finally, the resolved principal components are correlated with independent reconstructions of natural and anthropogenic radiative forcing, i.e., volcanic, solar and greenhouse gas forcing. The dominant pattern of variability in winter resembles the well-known North Atlantic Oscillation pattern. Its pressure, temperature, and precipitation fields explain 25.2% of the total climate variability over the studied area. The second pattern (16.8%) is similar to a blocking centred over Scandinavia associated with cold (warm) and dry (wet) conditions over Northern (Southern) Europe. Spring patterns are very similar, however, they explain less variability. Summer (autumn) patterns are more complex, revealing a blocking (trough) for combined EOF1 and blockings in case of EOF2 situated over Central Europe. Again, explained variances are reduced compared with the winter patterns.
The study shows that paleoreanalyses are a useful tool to study the variability of climate patterns on much longer time scales than offered by classical reanalyses. However, one has to take into account the uncertainties of the reconstructions.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1637 Regional climate change
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005