One of the key objectives of ESCAPE-2 is the development and application of a “domain-specific language (DSL) concept for the weather and climate community in order to maximize flexibility, programmability and performance portability to heterogeneous hardware solutions across different weather and climate models”. The realization of this objective has been structured into several steps containing the definition of a DSL concept, the development of an open source toolchain, and the demonstration of its applicability. These steps have been described in deliverables D2.1-D2.5 [8, 4, 9, 5, 7]. Deliverable D2.6 at hand here reports on the usability and performance of applying the DSL toolchain and depends on the above list of previous deliverables. The aim, as formulated in task T2.4, is "an in-depth evaluation of the DSL in terms of usability and performance [...], including a comparison between the original code and the DSL version and their behaviour on different systems." 
Usability also has been discussed based on concrete algorithms of selected dwarfs in D2.4 [5] which are not repeated here but only summarized. Four main aspects of usability are considered: programmability, completeness, modularity and the ability to integrate the DSL solution into the model. In addition to the evaluation of usability by reviewing previous results and experiences there are now first performance measurements on GPUs available. These are presented in comparison with OpenACC and discussed with respect to their sensitivity and to the applied optimizations.