A new diagnostic for measuring the ability of atmospheric models to reproduce realistic low-frequency variability is introduced in the context of Held and Suarez’s 1994 proposal for comparing the dynamics of different general circulation models. A simple procedure to compute , the e-folding time scale of the annular mode autocorrelation function, is presented. This quantity concisely quantifies...

In Coupled Model Intercomparison Project Phase 5 (CMIP5) models, the zonal-mean tropospheric circulation shifts robustly poleward in the Southern Hemisphere extratropics in response to increased atmospheric CO2 concentrations. However, in the Northern Hemisphere (NH) extratropics, the circulation response to CO2 is largely absent in the zonal mean and is instead characterized by complex regiona...

The atmospheric state simulated by the National Center for Atmospheric Research (NCAR) Community Climate Model, version 3 (CCM3), is compared to that simulated by the NCAR Climate System Model, version 1 (CSM1). CCM3 is an atmospheric general circulation model that uses specified sea surface temperatures (SSTs) for a lower boundary condition. Observed monthly mean SSTs for 1979–93 were used in ...

The circulation response of the atmosphere to climate change–like thermal forcing is explored with a relatively simple, stratosphere-resolving general circulation model. The model is forced with highly idealized physics, but integrates the primitive equations at resolution comparable to comprehensive climate models. An imposed forcing mimics the warming induced by greenhouse gasses in the low-l...

The carbon monoxide cycle is studied by incorporating the known and hypothetical sources and sinks in a tracer model that uses the winds generated by a general circulation model. Photochemical production and loss terms, which depend on OH radical concentrations, are calculated in an interactive fashion. The computed global distribution and seasonal variations of CO are compared with observation...

The principal goal of the Atmospheric Radiation Measurement Program (ARM) is to obtain data that will be useful in improving the parameterization of clouds in General Circulation Models (GCMs). With this goal in mind, an extensive field program has been initiated in Oklahoma to obtain the necessary measurements. The field site consists of a central location where an enormous set of cloud and ra...

The formation of tropical storms in a low-resolution Atmospheric General Circulation model is studied over the western North Pacific region during the June–October season. The model simulates the mean annual cycle of storm number in this basin quite well. Time-dependent composites of the storms are formed and analyzed, with a focus on the temporal evolution of quantities averaged in space aroun...

5 The influence of clouds on the large-scale atmospheric circulation is examined in numerical 6 simulations from an atmospheric general circulation model run with and without atmospheric 7 cloud radiative effects (ACRE). 8 In the extratropics of both hemispheres, the primary impacts of ACRE on the circulation 9 include: 1) increases in the meridional temperature gradient and decreases in static...