Climate Signals on the Regional Scale Derived with a Statistical Method: Relevance of the Driving Model’s Resolution

Abstract

When assessing the magnitude of climate signals in a regional scale, a host of optional approaches is feasible. This encompasses the use of regional climate models (RCM), nested into global climate models (GCM) for an area of interest as well as employing empirical statistical downscaling methods (ESD). In this context the question is addressed: Is an empirical statistical downscaling method capable of yielding results that are comparable to those by dynamical RCMs? Based on the presented ESD method, the comparison of RCM and ESD results show a high amount of agreement. In addition the empirical statistical downscaling can be applied directly to a GCM or a GCM-RCM cascade. The paper aims at comparing the consequences of employing various CGM-RCM-ESD combinations on the derived future changes of temperature and precipitation. This adds to the insight on the scale dependency of downscaling strategies. Results for one GCM with several scenario runs driving several RCMs with and without subsequent empirical statistical downscaling are presented. It is shown that there are only small differences between using the GCM results directly or as a GCM-RCM-ESD cascade.

The Weather Generator Used in the Empirical Statistical Downscaling Method, WETTREG

“…Frequently, the development stages were published in reports to the funding agencies (e.g., [25,28,29,55,56]). This was accompanied by peer reviewed papers (e.g., [23,24,26,27,41,57]) in which important aspects of the WETTREG method and its evolution can be found.…”

“…Most of these studies are available as reports, i.e., not in peer-reviewed journals, e.g., [51][52][53]. A comparison for a subregion from Germany has been published in [24].…”

“…Recently, also, Regional Climate Models (RCMs) have been run for a similarly large area, enabling WETTREG to use them as an alternative input data source [24]. Eight upper air fields, i.e., geopotential height (at 1,000, 850, 700 and 500 hPa), temperature and humidity at 850 and 500 hPa are extracted for the description of the 12 UTC conditions, as is simulated by the circulation model.…”

“…[23,24]). The method's development dates back to projects in the mid-1990s [25] and is in a process of continuous refinement [26,27].…”

Regionale Klimamodellierung

“…In weiteren Projekten wurden Klimarechenläufe auch bis zu einer Auflösung von 7 km, teilweise 2,8 km verfeinert . In der Klimafolgenforschung und für verschiedene Anwendungen setzt man zudem statistische oder statistisch-dynamische Regionalisierungen globaler Modelle ein (Enke et al 2005;Spekat et al 2007Spekat et al , 2010Kreienkamp et al 2011aKreienkamp et al , 2013. (Heise et al 2003), VEG3D (Schädler 2007), CLM2 (Davin et al 2011;Edouard et al 2011) und REMO-iMOVE (Reick et al 2013;Wilhelm et al 2014).…”