,

,

,

with initial conditions

,

Here represents time, stands for the strength of the symmetric, globally averaged westerly wind current, and and are the cosine and sine phases of a chain of superposed waves transporting heat toward the poles. and are thermal forcings: is the symmetric cross-latitude heating contrast and accounts for the asymmetric heating contrast between oceans and continents; is the angular frequency. The parameters of interest are the thermal forcings and their angular frequency; the values of the parameters and are set to 20 and 18.