Radiative‐dynamical climatology of the first‐generation Canadian middle atmosphere model

The Canadian Middle Atmosphere Modelling (MAM) project is a collaboration between the Atmospheric Environment Service (AES) of Environment Canada and several Canadian universities. Its goal is the development of a comprehensive General Circulation Model of the troposphere‐stratosphere‐mesosphere system, starting from the AES/CCCma third‐generation atmospheric General Circulation Model. This paper describes the basic features of the first‐generation Canadian MAM and some aspects of its radiative‐dynamical climatology. Standard first‐order mean diagnostics are presented for monthly means and for the annual cycle of zonal‐mean winds and temperatures. The mean meridional circulation is examined, and comparison is made between the steady diabatic, downward controlled, and residual streamfunctions. It is found that downward control holds quite well in the monthly mean through most of the middle atmosphere, even during equinoctal periods. The relative roles of different drag processes in determining the mean downwelling over the wintertime polar middle stratosphere is examined, and the vertical structure of the drag is quantified.