Cloud computing has drastically changed the way in which IT resources can be consumed. The properties of clouds – elasticity, pay-per-use, and standardization of the runtime infrastructure – enable cloud providers and users alike to benefit from economies of scale, faster provisioning times, and reduced runtime costs. However, to achieve these benefits, application architects and developers have to respect the characteristics of the cloud environment. To reduce the complexity of cloud application architecture and design, we propose a pattern-based approach for cloud application architecture and development. We defined a pattern format to describe the principles of cloud computing, available cloud offerings, and cloud application architectures. Based on this format we developed an architectural pattern language of cloud-based applications. Through interrelation of patterns for cloud offering descriptions and cloud application architectures, developers are guided during the identification of patterns applicable to their problems. We cover the proceeding how we identified patterns, give an overview of previously discovered patterns, and introduce one new pattern. Further, we propose a framework for the organizations of patterns and the guidance of developers during their instantiation.