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Overview

The Neelin-Zeng Quasi-Equilibrium Tropical Circulation Model (QTCM), developed at the UCLA Department of Atmospheric Sciences by J. David Neelin and Ning Zeng [1, 2], is an intermediate-level atmospheric model that assumes the atmosphere is in a state of ``quasi-equilibrium''. By quasi-equilibrium, we mean that the changes in energy at the large-scales are roughly balanced by changes in energy associated with small-scale convective activity. Thus, the vertical profiles of temperature are assumed to be ``defined'' by a ``reference'' profile; the model will restore departures from that profile back to the reference profile.

The assumption of quasi-equilibrium is valid in the tropical deep convective regions, where the atmosphere is unstable and highly convective throughout the tropospheric column. Away from the deep tropics, dry dynamics predominate, and the quasi-equilibrium assumption is generally no longer valid. However, because the QTCM provides a robust treatment of the moist dynamics that dominate in the tropics, the QTCM should also provide a reasonable description of atmospheric dynamics in areas where quasi-equilibrium does not locally apply, up to approximately one Rossby radius away from the tropics.

By making the quasi-equilibrium assumption, the QTCM does not divide the atmosphere into multiple vertical layers as most general circulation models do. This gains simplicity and dramatically cuts computational time, while retaining a realistic simulation of the climate system. The current version takes approximately eight minutes of wall-clock time to run one year of model simulation on a SUN Ultra 2 workstation.

The current version of the model includes the following major features:


next up previous contents
Next: Model Spatial and Temporal Up: Introduction and Model Description Previous: Introduction and Model Description

Johnny Wei-Bing Lin
Mon Jun 30 12:27:46 PDT 1997