15C.2
Spatial and temporal variability of spring phenology in Europe in relation to large-scale atmospheric circulation
Rein Ahas, University of Tartu, Tartu, Estonia; and J. Jaagus and A. Aasa
We studied European spring phenology with aim to analyse spatial and temporal variability of phases in relation to large-scale atmospheric circulation. Studied early spring, spring and summer season phenological phases were selected from the European phytophenological database of the EU 5th Framework programme project "POSITIVE". We used phytophenological data from Austria, Check, Estonia, Germany, Latvia, Poland, Russia, Slovenia, Switzerland and Ukraine with a time period between 1951-1998. Data on large-scale atmospheric circulation consisted a subjective circulation classification worked out in Arctic and Antarctic Research Institute of St. Petersburg (Wangenheim 1952, Girs 1971); two NAO indices (Hurrell & van Loon 1997, CAS 2001, Jones et al. 1997, CRU 2001); Arctic Oscillation index (Thompson & Wallace 1998); teleconnection indices for the Northern Hemisphere (CPC, 2001). Relationaships of phenological phases and atmospheric circulation has similarities with climatic seasons and temperature patterns studied (Jaagus et al 2002). Early spring phases depend more on intensity of westerlies during the second half of winter. The higher intensity of the zonal circulation the earlier ends winter and starts early spring. The influence of atmospheric circulation on start date of spring and spring phases is weaker than in the previous period. Start date of summer phases has significant correlations with frequency of circulation forms according to Wangenheim-Girs and with teleconnection indices but not with NAO indices. Due to different start dates at different latitudes and longitudes, the influence of atmospheric circulation reveals at different months.
Session 15C, Phenology: Climate Variability and Adaptation Issues
Friday, 1 November 2002, 1:00 PM-2:30 PM
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