"expressing a fundamental structural organization schema for software systems. It provides a set of predefined subsystems, specifies their responsibilities, and includes rules and guidelines for organizing the relationships between them."
The book describes 8 architectural patterns that mostly follow this definition.
The Patterns Almanac[ISBN 0-201-61567-3 (alternate, search)] lists 79 architectural patterns. Not all of these patterns meet the POSA1 definition. According to Linda Rising, the developer of the Patterns Almanac, the categorization of the patterns in the patterns almanac was left to the authors.
A much broader view of an architecture pattern might emerge if we consider that the purpose of the software architecture is to ensure that the system meeta the goals of the stakeholders with respect to various software qualities such as maintainability, scalability, testability, etc. A full taxonomy of software qualities has been published by the SEI: http://www.sei.cmu.edu/str/taxonomies/view_qm.html And there are other issues such as security that may cross-cut the design of a large system.
However, the difficulty is we want to make distinctions as clearly as possible between a 'design pattern' and an architectural pattern. Clearly, design patterns will also have an impact on these various software qualities, so what is it that then distinguishes an architecture pattern from a design pattern?
A different way of looking at the difference between a design pattern and an architecture pattern is think about the questions considered in the development of the software architecture. These include things like:
Amnon H. Eden, Rick Kazman: Architecture, Design, Implementation: http://www.eden-study.org/articles/2003/icse03.pdf
It gives a formal distinction between architecture, design, and implementation based on the so-called Intension and Locality criteria. Design and architecture specifications (e.g. patterns) are both intensional but design has local effects while architecture considers program-wide properties (therefore is non-local).