Deliverable D8a: Development of the rule-based downscaling methodology for BIOCLIM Workpackage 3. Work Package 3, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)

摘要

One of the tasks of BIOCLIM WP3 was to developuda rule-based approach for downscaling from theudMoBidiC model of intermediate complexity (seeudRef.1) in order to provide consistent estimates ofudmonthly temperature and precipitation for the specificudregions of interest to BIOCLIM (Central Spain, CentraludEngland and Northeast France, together with Germanyudand the Czech Republic). Such an approach has beenuddeveloped and used in a previous study funded by Nirexudto downscale output from an earlier version of thisudclimate model covering the Northern Hemisphere only,udLLN 2-D NH, to Central England, and evaluated usingudpalaeoclimate proxy data and General CirculationudModel (GCM) output for this region. This previous studyud[Ref.2] provides the starting point for the BIOCLIMudwork.udA statistical downscaling methodology has beenuddeveloped by Philippe Marbaix of CEA/LSCE for useudwith the second climate model of intermediateudcomplexity used in BIOCLIM – CLIMBER-GREMLINSud(see Ref.1). This statistical methodology is describedudin Deliverable D8b [Ref.3]. Inter-comparisons of all theuddownscaling methodologies used in BIOCLIM (includingudthe dynamical methods applied in WP2 – see Ref.4 andudRef.5) are discussed in Deliverable D10-12 [Ref.6].udThe rule-based methodology assigns climate states orudclasses to a point on the time continuum of a regionudaccording to a combination of simple thresholdudvalues which can be determined from the coarseudscale climate model. Once climate states or classesudhave been defined, monthly temperature andudprecipitation climatologies are constructed usingudanalogue stations identified from a data base ofudpresent-day climate observations. The most appropriateudclimate classification for BIOCLIM purposes is theudKøppen/Trewartha scheme (Ref.7 ; see Appendix 1).udThis scheme has the advantage of being empirical, butudonly requires monthly averages of temperature andudprecipitation as input variables.