The effect of simulated shallow convection in the tropics and extra-tropics

Shallow convection strongly interacts with deep convection in the tropics and therefore to a degree it contributes to the large-scale mechanisms of the ITCZ. The moistening effect of shallow convection in the tropics is often referred to as pre-conditioning for deep convections and plays an important role for the diurnal cycle of precipitation, especially over the land. On the other hand, a transition from stratocumulus to shallow convection and post-frontal shallow convections affect the cloudiness, radiation budget and precipitation in the extra-tropics. In this study, the role of shallow convection is focused on to investigate the forecast performance of the global numerical weather prediction (NWP) model of the Japan Meteorological Agency (JMA) under the KAKUSHIN project (funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology). The comparison of the model forecast with satellite data helped to give a more accurate estimation of the JMA global NWP model, although the satellite data may have unique characteristics in some situations. The preliminary results suggest that there seems to be an inadequate shallow convection trigger and a sensitive balance between deep and shallow convection in the JMA global model, which causes a dry bias in the middle troposphere. The forecasted results and the further impact of the revised convection scheme will be analyzed and discussed.