Abstract
By parameterizing various types of heat sources (sinks) a linear model of coupled oceanatmospheric system has been established. By means of frequency analysis it is shown that in this model there are two different types of waves, one corresponding essentially to the travelling Rossby wave in non-adiabatic atmosphere which has a period of several days, and the other is a slowly varying wave which are driven by anomaly heating in ocean. Evidently the existence of this short time-scale weather process presents difficulties for the long-range numerical weather forecasting, because the evolution of the long-range weather process of smaller amplitude will be distorted by the short-range weather process of large amplitude. In order to overcome these difficulties the travelling Rossby wave are filtered as a "noise" from the model of the long-range weather forecast. A simple method of filtering is given. Then a practical model for predicting the monthly mean anomalous fields of 500mb geopotential height and earth's surface temperature is given and the experimental results are reported. This tentative study shows that the filtering method mentioned in this paper may be a promising way for making long-range weather forecast.
