Estimate of monthly mean predictability in the tropics form observations

Abstract

A method of separating the contributions from slowly varying boundary forcing and internal dynamics (e.g. intraseasonal oscillations) that determine the predictability of the monthly mean tropical climate is presented. Based on 33 years of daily low level wind observations and 24 years of satellite observations of outgoing long wave radiation, we show that the Indian monsoon climate is only marginally predictable, as the contribution of the boundary forcing in this region is relatively low and that of the internal dynamics is relatively large. It is also shown that excluding the Indian monsoon region, the predictable region is larger and predictability is higher in the tropics during northern summer. Even though the boundary forced variance is large during northern winter, the predictable region is smaller as the internal variance is larger and covers a larger region during that period (due to stronger intraseasonal activity).