Surrogate climate-change scenarios for regional climate models

A methodology is presented for generating surrogate climate-change scenarios with a regional climate model. The procedure is simple to implement and dynamically consistent. It entails (i) adopting a realized or simulated atmospheric flow evolution and (ii) prescribing specific thermodynamic modifications of this realization to a regional model's initial fields and externally-specified time-dependent lateral boundaries fields. The resulting scenarios can be used for process and parameterization studies, to calibrate the regional response to a putative global climate change, and to intercompare different models. The approach is illustrated with two month-long regional climate model simulations. The experiment is designed to explore the response within Europe to a pseudo-global warming of 2 K with an accompanying increase in atmospheric water vapor content. Analysis reveals that there is a spatially-differentiated preciptation increase consonant with the domain-averaged increase of about 16% in the water vapor content.