LINEAR VERSUS NONLINEAR TECHNIQUES IN DOWNSCALING

Standard linear and nonlinear downscaling models are compared using id entical atmospheric circulation forcing fields. The target variables c hosen were observed daily values of average temperature (TAV), precipi tation (PRC), and vapor pressure (HPR) at a Central European station. Being without much sophistication, both models show acceptable perform ance on this time scale only for TAV and HPR; PRC, which behaves in a predominantly nonlinear fashion, handled very poorly. By considerably refining the evaluation it is nevertheless possible to distinguish sig nificant differences between the 2 models and, with the nonlinear mode l, to describe specific rainfall conditions. We argue that this differ ence is caused by the limitations of the linear approach, and discuss how this might affect the downscaling of nonlinear quantities in gener al.