de Elvira, A. R., and P. Lemke, 1982: A Langevin equation for stochastic climate models with periodic feedback and forcing variance. Tellus, 34, 313-320.

Abstract: The concept of stochastic climate models developed by Hasselmann is generalized to include periodic feedback coefficients and random forcing with periodic variance, in order to take into account the seasonal variability of the mean atmosphere-ice-ocean interaction and of the atmospheric noise. Our results show marked departures from the original model, seen as seasonal modulations of the amplitudes of the covariances both with respect to seasonal and to lag times.