The role of the balance between deep convection and shallow convection in the JMA High-Resolution Global NWP Model

It is widely understood that cumulus convection plays a key role in determining the vertical structure of temperature and moisture fields of the atmosphere. Under the KAKUSHIN project (funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology), the forecast performance of the global numerical weather prediction (NWP) model of the Japan Meteorological Agency (JMA), which is utilized to evaluate severe weather events in future climate, was investigated.

To represent cumulus convection adequately, a cumulus convection scheme in the NWP model and its characteristics have to be evaluated. This study analyzed both suppressed and active convection forecasts in tropics with the aid of the CloudSat satellite observational data and experimental forecast during Tropical Ocean Global Atmospheric Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE).

The preliminary results suggest that there is an imbalance between deep convection and shallow convection. In our model, less contribution of shallow convection including cumulus congestus, influences to maintain temperature and moisture profile of the atmosphere, which results into the dry bias in the middle troposphere. Further results of the investigation and impact of the modifications to the parameterizations will be evaluated and discussed.