Hybrid Isentropic Coordinate Modeling at the University of Wisconsin - Madison

In the 1970s, Professor Donald Johnson and his research group at the University of Wisconsin – Madison (UW) initiated a research program to develop and utilize hybrid isentropic coordinate models for the study of atmospheric circulations on a wide range of scales. In this paper we provide an overview of hybrid isentropic coordinate modeling activities at the UW that have proceeded through a hierarchy of models from a series of preliminary channel models to the global model in use today. Model development has entailed studies of a wide variety of numerics employing both Eulerian and semi-Lagrangian numerics and different algorithms for boundary layer and dry and moist convective parameterizations. Ensuring the accuracy of the transports of energy, entropy, water vapor and other trace constituents has guided development.

Emphasis will be on results from the UW global hybrid model illustrating the excellent transport characteristics of isentropic coordinate models and demonstrating the capabilities of hybrid isentropic coordinate models for both numerical weather prediction and climate simulation. Results from the current application of the UW global hybrid model will also be presented. The UW hybrid isentropic coordinate model comprises the meteorological/transport component of the Real-time Air Quality Modeling System (RAQMS). RAQMS, a global meteorological and chemical modeling system, is run daily at the UW assimilating remote and in-situ observations of atmospheric chemical composition and providing global five day chemical and aerosol forecasts on a 1x1 degree grid. Spaced-based observations of column ozone, 3-d distributions of stratospheric ozone and aerosol optical depth are currently assimilated in RAQMS. RAQMS forecasts have frequently been used to provide flight planning support for scientific field missions, and by other research groups as initial conditions and lateral boundary conditions.