On long-term evolution of seasonal precipitation in southwestern Europe
Annual cycles in long time series of precipitation from sixteen southwest European observatories have been analysed using complex demodulation. The stations have been clustered into two distinct regions and a hybrid one. They are referred to as the southwestern Europe precipitation Atlantic regi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1996-09-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/14/976/1996/angeo-14-976-1996.pdf |
| Summary: | Annual cycles in long time series of
precipitation from sixteen southwest European observatories have been analysed
using complex demodulation. The stations have been clustered into two distinct
regions and a hybrid one. They are referred to as the southwestern Europe
precipitation Atlantic regime (SEPAR) and the southwestern Europe precipitation
Mediterranean regime (SEPMER), with the hybrid regime referred to in terms of
the mean amplitude ratios between semiannual and annual rainfall components.
Some evidence of linking between seasonal cycle harmonic amplitudes and the
zonal circulation has been found for SEPAR stations and a more obscured
relationship for the SEPMER region. Within the SEPAR region the strength of the
relationship is diminished towards the north. A trend analysis of the amplitudes
against time since 1920 has also been carried out and the results reveal a
divergent pattern in trends between annual and semiannual component amplitudes
for the SEPAR region. In fact, both an increasing annual-amplitude trend and a
decreasing semiannual-amplitude trend are observed, in each case statistically
significant. The fact that the seasonal cycle variability of rainfall in
southwestern Europe becomes more sensitive southwards to changes in atmospheric
zonal circulation over the North Atlantic might, in our opinion, be related to
the swing of the circumpolar vortex. |
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| ISSN: | 0992-7689 1432-0576 |