Expert Knowledge and Multivariate Emulation: The Thermosphere–Ionosphere Electrodynamics General Circulation Model (TIE-GCM)

The thermosphere–ionosphere electrodynamics general circulation model (TIE-GCM) of the upper atmosphere has a number of features that are a challenge to standard approaches to emulation, including a long run time, multivariate output, periodicity, and strong constraints on the interrelationship between inputs and outputs. These kinds of features are not unusual in models of complex systems. We show how they can be handled in an emulator and demonstrate the use of the outer product emulator for efficient calculation, with an emphasis on predictive diagnostics for model choice and model validation. We use our emulator to “verify” the underlying computer code and to quantify our qualitative physical understanding.