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| Titel |
Precipitation Variability in Finland and Relationships with Climate Teleconnection Indices |
| VerfasserIn |
Masoud Irannezhad, Hannu Marttila, Björn Klöve |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072296
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| Zusammenfassung |
| Annual, seasonal, and monthly variations in precipitation over Finland during the period
1911-2011 were evaluated using spatially interpolated monthly precipitation records at 237
stations with more than 10 years data (of which 166 stations with over 30 year data). The
non-parametric Mann-Kendall test and Fourier series method were used to determine
significant historical trends and cyclic patterns in precipitation, respectively. Further,
relationships between precipitation variability and different climate teleconnection indices
were analyzed based on Spearman’s correlation coefficient (rho). At 5% significance level (p
< 0.05), the annual precipitation over Finland increased by 0.93 (mm/year), and associated
strongly with the East Atlantic/West Russia (EA/WR) pattern (rho = -0.41). However, there
were spatial differences between regions from north to south and east to west. Time cycle
(λ) for annual precipitation was estimated about 180 years (R2 = 0.19), and year
1966 was indicated as turning point from negative (dry) to positive (wet) phase.
Analysis of seasonal precipitation indicated increasing trends for both winter by
0.51 (mm/year) and autumn by 0.48 (mm/year), while no clear trend was found for
spring and summer precipitation (p > 0.05). The most significant correlation of
winter precipitation was found with the North Atlantic Oscillation (NAO) index
(rho = 0.59, p < 0.05). The Scandinavia (SCA) pattern was the most significant
teleconnection index influencing the precipitation variations in both spring (rho = -0.40, p <
0.05) and summer (rho = -0.35, p < 0.05) seasons. There was a strong negative
relationship between autumn precipitation and the EA/WR pattern (rho = -0.25, p < 0.05).
The time cycles of seasonal precipitation were about 188 years for winter, 4 years
for spring, 6 years for summer, and 135 year for Autumn, where R2 > 0.10.
Monthly precipitation analysis determined significant increasing trends for January,
February, March, November, and December months, and no clear trend for the
other months. Maximum increasing trend was for January by 0.23 (mm/year) and
minimum increasing was found for November by 0.14 (mm/year). The precipitation
variability in January, February, May, June, August, September and October showed
strong negative correlation the SCA pattern. The NAO was the main teleconnection
index affecting precipitation in March and December, while precipitation in April
and July was strongly in relation to the EA/WR pattern. The East Atlantic (EA)
pattern was the most significant teleconnection index that influenced precipitation
in November. Periodicity analysis of monthly precipitation indicated long time
cycles for December-April (120 < λ < 225 years), and short time cycles for
May-November (2 < λ < 8 years). Results clearly indicate that precipitation
patterns have changed in Finland during last decades and precipitation is controlled by
various climate teleconnections, which has major influence on water resources and
management.
Keywords: Precipitation, trend, teleconnection indices, cyclic pattern, Finland |
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