2002 Annual

Wednesday, 16 January 2002: 4:45 PM
Stationary Wave Responses to Climate Change in the GFDL GCM
Mingfang Ting, University of Illinois, Urbana, IL; and R. Joseph and P. J. Kushner
Regional climate changes due to greenhouse gas increases in the atmosphere are closely related to the changes in the atmospheric stationary wave patterns. In this study, the stationary wave responses to the greenhouse gas increase in the GFDL Climate Dynamics Group coupled GCM are studied. In particular, stationary wave changes from a control simulation with fixed pre-industrial CO2 and sulphate aerosol concentrations and from three ensemble "IPCC IS92a" scenario simulations with gradually increasing concentrations are examined. The coupled-model simulations are compared to linear and non-linear baroclinic stationary wave models.

The stationary wave changes in January and July is found to be very robust. In January, anticyclone pairs in the eastern subtropical Pacific and cyclone pair over the subtropical Western Pacific, and a deep low over the Aleutian region in the upper troposphere are found. The deep low over Aleutian region and the anticyclone over the eastern subtropical Pacific induces an eastward extended subtropical jet which bring more precipitation to Northwest US. The linear model reproduces the stationary wave changes in the GCM fairly well. The main contributors to the enhanced subtropical jet are diabatic heating and stationary non-linearity. It is also noted that the stationary wave changes in midlatitudes are strongly equivalent barotropic, indicating that global warming does not greatly alter the transport of heat by midlatitude stationary eddies. The non-linear baroclinic stationary wave models will help in understanding the nature of the stationary non-linearity forcing seen in the linear model results. We will also explore the seasonality of the stationary wave changes and their maintenance using the linear and nonlinear models.

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