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| Titel |
Changes in the length of the seasons over the Iberian Peninsula for future conditions from ENSEMBLES regional climate models ensemble |
| VerfasserIn |
N. Lopez de la Franca, E. Sánchez |
| 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 |
250068519
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| Zusammenfassung |
| The estimation of spring season onset and length variation is an important issue because it is
related with the variability of growing season and also affects ecosystems and crop
production. Many studies show earlier onset and longer length spring trends in the past years
compared with the XXth century. Nevertheless, the study of the rest of seasons is also
important, because many natural hazards and natural systems are not only are related with
spring, like wildfire activity or floods in the Mediterranean areas. The overall increase in
temperature shown in all the future climate projections for the XXIst century is
expected to be translated into an increase of summer duration and a reduction of
winter length compared with present-climate conditions. There is more uncertainty
on what is going to happen on the transitional seasons (spring and autumn), how
are they going to be displaced, reduced or increased, from a mid-latitude climatic
perspective.
The main aim of this study is to define the onset and end for the four seasons and its
change in the future over the Iberian Peninsula (IP) as modelled from eleven Regional
Climate Models (RCMs) with high spatial resolution (25 km2) from the European Project
ENSEMBLES. The analysis periods are 2021-2050 and 2071-2100 under the A1B emissions
scenario. First, an evaluation of their performance during present climate period
(1961-1990) is done, comparing the SPAIN02 gridded temperature dataset and ERA-40
reanalysis.
There are many methods that use phenological, climatological criteria or the combination
of them to estimate the spring onset. Methods are usually based in fixed temperature and/or
precipitation thresholds, or in change of the annual cycle of temperature, in terms of its phase
and amplitude. Here, a threshold-based model is used in the onset season definition, not only
for spring, but for all the seasons. To avoid the potential arbitrariness or location-dependence
of using a fixes threshold, we propose a criteria to define the onset of the seasons from
25th and 75th temperature percentiles at each point, computed for present-climate
period. Both maximum and minimum daily temperatures are used to obtain these
indexes.
Results show that summer season tends to be longer and winter to be shorter in the
future for all the models. Autumn also exhibit an increase in its length, meanwhile
spring show a more uncertain behaviour, as some models give a small decrease, and
other a small increase, over the IP, for 2021-2050 period. The start of spring is
earlier, meanwhile the autumn start is delayed. Winter starts later and ends earlier.
For the far future period (2071-2100), these results present a pronounced similar
behaviour, with spring showing a more common pattern to a slight increase of its
duration. |
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