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| Titel |
Future of the hydrological cycle over Europe - Lessons learned from a surrogate climate change scenario |
| VerfasserIn |
E. M. Zubler, D. Lüthi, C. Schär |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060956
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| Zusammenfassung |
| The hydrological cycle is known to be a very sensitive component of the climate system. It
has been shown that the variability of the atmospheric moisture content in the mid-latitudes
largely depends on temperature rather than relative humidity. Given the higher water holding
capacity of the atmosphere in a warmer climate, global circulation models suggest an
invigoration of the hydrological cycle in the future, resulting in an increase of global mean
precipitation.
In this study, a surrogate climate change scenario is used to investigate the hydrological
impact of a warming increment of 3Â K imposed on the large-scale circulation. For this
purpose, the regional climate model COSMO-CLM is applied at a horizontal resolution of
50Â km over Greater Europe. It is driven by the ERA-interim reanalysis over the period from
1989 to 2009. The control simulation (CTRL) uses the original forcing of the reanalysis at
its lateral boundaries, whereas the scenario (W3K) includes the aforementioned
temperature increment. The latter is associated with an increase of the atmospheric
moisture content in W3K according to the Clausius-Clapeyron relation (roughly
+21%).
The large-scale warming leads to a substantial upward shift of the freezing level by about
400Â m in winter over European land with an attendant reduction of ice, snow and graupel
below 700Â hPa. As a consequence, snowfall becomes less frequent in W3K. The ratio of
snowfall to total precipitation declines by 10–30% over Central and Eastern Europe. The total
amount of precipitation increases by about 15% on average. As a result of the reduced
snowfall, the surface albedo decreases by more than 20% in large parts of Europe, leading to
a strong snow-albedo feedback that amplifies the local warming beyond the imposed
3Â K.
In summer, the effective warming near the surface is found to be below 2Â K in Central
and Eastern Europe. This can be attributed to an increased fraction of low clouds
(+4–6%). This effect reduces the downward surface shortwave radiation by more than
10Â WÂ m-2 on average in summer. Furthermore, deep convective becomes more frequent,
particularly in summer, leading to a higher cirrus cloud cover over large parts of Europe. |
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