The Role of Tropical Diabatic Heating for the Indian Monsoon

Seasonal ensemble re-forecast experiments are performed each year over the satellite era in order to diagnose the role of diabatic heating over the tropical Indo-Pacific for the Indian Monsoon. Using the Climate Forecast System version 2, ten-member ensemble re-forecasts are initialized in early May and analyzed over June through September. The re-forecasts are then repeated with heating/cooling fields added to the temperature tendencies produced by the model over the tropical Indo-Pacific region, an approach that alters the total diabatic heating without interfering with internal model feedbacks. The added fields are obtained from an iterative process that greatly reduces the error in the seasonal mean, trend and parabolic fit of the ensemble mean model diabatic heating (compared to reanalysis estimates). A significant reduction in bias is found in the global circulation in terms of both the climatological seasonal cycle and inter-annual variability. There is an improvement in the representation of teleconnections between the Indian Monsoon and tropical diabatic heating. This provides an improved estimate of potential predictability of the Indian Monsoon and reinforces the need to improve the representation of diabatic heating in climate models.