 |
| Titel |
The annual cycle of intensity and frequency of extreme precipitation events across the UK in observations and future projections |
| VerfasserIn |
Anne Schindler, Douglas Ma, Jurg Luterbacher |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055479
|
|
|
|
|
|
| Zusammenfassung |
| Precipitation in the UK shows a pronounced annual cycle. For the assesment of past, present
and future agricultural and hydrological impacts it is important to study intensity and
frequency of extreme events together with their spatial and temporal occurrence throughout
the year. Especially in a downscaling approach it is important to model intensity and
occurence frequency independently, since different predictors might act differently on
intensity and occurrence.
We design a statistical model based on extreme value statistics (EVS) and fit the statistical
model to a selection of daily precipitation series based on the MIDAS land surface
observation data provided by the British Atmospheric Data Centre. The selection comprises
689 rain gauges covering the whole UK and a period from 1961 to 2006. We study
spatial and temporal patterns of the annual cycle of intensity and rate of occurrence
respectively.
Here we model extreme precipitation in the UK as a Poisson process with a non-stationary
threshold. We determine the threshold by normalizing the data relative to the “day of the
year” mean precipitation, then calculating a high quantile, e.g. 95% quantile, of the
normalized data and by transforming these values back to the original scale we obtain the
threshold values for each day of the year. We use a sinusoidal model for the location and scale
parameter of the corresponding generalized extreme value (GEV) distribution and a constant
shape parameter.
In a second step we validate the representation of the annual cycle of extreme precipitation
events simulated by 14 regional climate models (RCMs) with a resolution of 25km,
used in the ENSEMBLES project. As a reference data set we use the gridded UK
Metoffice data set. We fit the statistical model to the reference data set and the
ERA40 driven RCMs and the annual cycle of intensity and frequency simulated
by the RCMs with the observational results. We then assess future changes of the
local scale annual cycle in extreme precipitation in the ensemble of RCMs. To this
end we analyse the projection of the validated RCMs driven by the SRES scenario
A1B.
We detect a shift in the annual cycle of the frequency or a trend in the annual cycle of the
intesity of extreme precipitation events. |
|
|
|
|
|
|