Estimate of predictability of monthly means in tropics from observations

A method of separating the contributions from slowly varying boundary forci ng and internal dynamics (e.g. intraseasonal oscillations) that determine t he 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 shoes that the Indian mons oon climate is only marginally predictable, as the contribution of the boun dary forcing in this region is relatively low and that of the internal dyna mics is relatively large. Pt is also shown that excluding the Indian monsoo n region, the predictable region is larger and predictability is higher in the tropics during northern summer. Even though the boundary forced varianc e 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).