Requirements patterns for context aware system is challenging due to dynamic and ambiguous nature of context data which remain poorly characterized. A significant amount of research is being done on formalizing context aware systems. However, only few works has been done on requirement patterns which are mandatory to derive complete, consistent and deployable specifications for context data. Since context aware systems with its applications and simulation are still in pilot study. There is a need of formalizing context properties and a methodology to drive the contextual requirements in the system. Further to focus the research problem, empirical study was carried out to investigate context aware pattern properties and different context aware pattern aspects. The contribution of this paper work is to propose ontology based context aware requirement patterns (CaRePa). This CaRePa compared with existing models in context aware patterns. New set of context properties are identified and merged with the CaRePa template. Verification can be performed with the model created using ontology for context aware requirement patterns.