WG4: Extremes
Inventory
In the first phase, an inventory of extreme definitions, downscaling methods and validation measures will be carried out.
The inventory of extreme definitions will build on inventories of earlier projects (e.g. STARDEX, EMULATE), modified and extended to meet the needs of VALUE.
The inventory of downscaling methods will encompass the range of state-of-the-art RCMs, empirical statistical downscaling methods, and MOS methods. Additionally, the inventory will search for new methods based on stochastic models and downscaling of PDFs. The inventory will group the methods according to the downscaling approach as well as to its applicability (e.g., number of downscaled variables, local vs. spatially distributed, time scales provided). The inventory will be based on a literature review of methods to downscale extremes.
A range of validation measures will be compiled with a focus on extreme events. For this purpose existing validation studies will be analysed and limitations will be identified. Guidelines will be compiled for the validation of extremes.
Validation
In a second phase, the actual validation will be carried out.
To enable a smooth and objective validation, the chosen measures will be coded as a software package (R, FORTRAN).
The validation of extremes will be carried out against the observational benchmark data set. To isolate GCM errors and to enable a comparison of observed and modelled weather sequences, perfect boundary conditions will be used. Empirical statistical downscaling methods will use predictors from ERA40 reanalysis, and RCMs – both for the validation of MOS SDS methods and for the validation of the RCMs themselves - will be forced by ERA40 reanalysis data. The validation of variability on long time scales will be carried out in a pseudo reality. Passing the pseudo reality validation is a minimum requirement for a downscaling method to be sensibly applied for climate change studies.
Development of methods
Based on the initial inventory, WG4 will identify key problems related to extremes. Possible approaches for improvements and possible new directions of research will be discussed. In a later stage, the results of the validation exercise will be integrated into the development. Possible directions of research are the development of downscaling methods for spatially extended extremes and MOS methods specifically for extremes.
A suite of software packages for a range of well performing state-of-the-art downscaling methods will be developed and made available for the public.
Guidelines on the strengths and limitations of state-of-the-art downscaling methods directed towards researchers applying downscaling methods will be compiled.
Years 1-4
- D2: Inventory of downscaling methods, validation studies and gaps of knowledge
- D4: A set of validation measures for the different aspects addressed
- D5: Validation results (publications in international peer-reviewed scientific journals, including a special issue)
- D6: 21st century scenarios for regional climate change in Europe, simulated within existing projects coordinated by VALUE, based on the best performing methods and tailored to specific end user needs
- D7: Tailored guidelines for downscaling scientists and end-users (scientific and non-scientific) on suitable downscaling methods for different purposes