HR: 09:45h
AN: GC51B-08    [Abstracts]
TI: Statistical Downscaling of Rainfall for Romania From six European GCMs for Present Day and Future Climate
AU: * Huebener, H
EM: huebener@met.fu-berlin.de
AF: Institute for Meteorology, Free University Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12165, Germany
AU: Cubasch, U
EM: cubasch@zedat.fu-berlin.de
AF: Institute for Meteorology, Free University Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12165, Germany
AB: Circulation Weather Types calculated from ERA40 SLP fields are correlated to rainfall for selected Romanian stations in the lower Danube catchment. The western, central, and eastern parts of the area show differing correlations between rainfall and CWTs in the observations. For all all regions and most CWTs, precipitation amount per rain day is larger in summer while occurrence frequency of rain days per CWT is larger in winter. Rain amount and frequency show high positive (negative) correlation with cyclonic (anti-cyclonic) days. In the western region rain amounts are highest for SE CWT, associated with synoptic disturbances originating from the central Mediterranean. In the central and eastern region N to E CWTs provide the highest rain amounts, associated with low pressure over the black sea and the eastern Mediterranean. SW to NW CWTs are negatively correlated with rain in the eastern part of the area due to diffluence south of the Carpathians. In the scope of the EU-Project ENSEMBLES, CWTs are also calculated using six European GCMs (BCC, NERSC, Norway; CNRM-CM3, CNRM, France; EGMAM, FU-Berlin, Germany; ECHAM5/MPI-OM1, MPI-M, Germany; HadGEM1, Hadley-Centre, UK; IPSL-CM4, Institute Pierre Simone Laplace, France). Comparison of the occurrence frequency of CWTs for present-day simulations to the ERA40 results shows a positive bias of W CWT in Romania, associated with a too strong northern polar low in all models. Additionally an overestimation of cyclonic and an underestimation of anti-cyclonic days is found in the models. This feature is consistent with a general tendency of GCMs to underestimate blocking situations. The annual cycle of CWTs for Romania is displayed in the different models in varying quality: while ECHAM5/MPI-OM shows an annual cycle close to observations, some of the other models are not suited to represent the annual cycle correctly. All models show an increase of anti-cyclonic days combined with a decrease of cyclonic days for the SRES A1B scenario when compared to the respective present-day simulation. For the other CWTs the signals are either not significant or differ between the participating models. With respect to future rainfall in the lower Danube basin a drying tendency is expected due to the shift from cyclonic to anti-cyclonic CWT occurrences.
DE: 1637 Regional climate change
DE: 1655 Water cycles (1836)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3337 Global climate models (1626, 4928)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting