Predictability of low frequency modes

Summary In this paper we propose a procedure for the extended integration of low frequency modes of the time scale of 30 to 50 days. A major limitation of the extended integrations arise from a contamination of low frequency modes as a result of energy exchanges from the higher frequency modes. In this study we show an example on the prediction of low frequency mode to almost a month which is roughly 3 weeks beyond the conventional predictability. This was accomplished by filtering the higher frequency modes from the initial state. The initial state included a time mean state and a low frequency mode. The sea surface temperature anomalies on this time scale and the annual cycle were also prescribed.The specific experiment relates to the occurrence of a dry and a wet spell in the monsoon region. The meridional passage of an anticyclonic circulation anomaly over the lower troposphere and the eastward passage of a negative velocity potential anomaly over the upper levels of the Indian monsoon, on this time scale, are reasonably predicted. The aforementioned experiment was carried out with the 1979 data sets of the global experiment. A second example during an anomalous southward propagation of the low frequency waves over the Indian monsoon region during 1984 was also reasonably predicted by this model. Suggestions for further experimentation on the predictability of low frequency modes are proposed.With 16 Figures