Research Topics in Typhoon Research Department


Sophistication of the nonhydrostatic atmospheric model and improvement of the associated data assimilation technique

Numerical study of severe storms using the non-hydrostatic model

A nonhydrostatic typhoon model is being developed aiming at understanding the physical mechanisms governing the genesis, intensification and decay of typhoons, which is a key task in improving typhoon forecasts


  • Improvement of the nonhydrostatic typhoon model


    The nonhydrostatic typhoon model under development has a multiply-nested movable mesh configuration with a two-way interactive nesting strategy and explicit microphysics to correctly represent typhoon inner-core structure and its evolution in a cost-effective manner. During the course of the model development, the model is integrated not only for a short term such as 24 hours but also for a long time period including initial development stage, landfall event and decaying process of typhoons to evaluate its performance as a typhoon forecast model and improve it further.
    　　　　　

    　Output of NHM Typhoon model

    　(Figure) Precipitation distribution simulated by the nonhydrostatic typhoon model（mm／hour）
    　　　　　

    　Inner-core Structure of Typhoon　

    　(Figure) Inner-core Structure of Typhoon
    Shaded in colors is the asymmetric pressure field with the asymmertic winds.

  • Introduction of the effect of air-sea interaction into the nonhydrostatic typhoon model


    The air-sea interaction is one of important factors to be incorporated into the numerical models for an accurate typhoon intensity forecast since the strong wind associated with a typhoon significantly reduces SST and subsequently the reduced SST suppresses the typhoon intensification. The cooling effect becomes more pronounced as the model resolution is increased and stronger winds are simulated. A mixed-layer ocean model developed at MRI (Meteorological Research Institute), is coupled to the MRI/NPD (Numerical Prediction Division) unified nonhydrostatic model with a horizontal resolution of 6 km and some preliminary numerical experiments are conducted for the case of Typhoon Bilis (2000). Figure gives an example of the model-generated SST distribution along with a corresponding observation. The model successfully reproduces the significant features of SST field such as a pronounced SST decrease to the right of the storm motion.
    　　　　　

    　Output of numerical simulation

    　(Figure) SST (shaded in color), sea surface pressure (contoured in blue) and cloud water (shaded in green) at hour 36 of the coupled model integration from 1200 UTC 20 August, 2000 (left panel) and SST estimated from 3-day average TRMM/TMI data (right panel).
    　　　　　

  • Improvement of typhoon vortex initialization method


    A set of bogus observations are created based on available typhoon vortex information and injected into the data assimilation procedure to introduce a realistic typhoon structure in the model initial fields. An optimal injection method of the bogus observations are being explored within the framework of the four-dimensional variational data assimilation method.
    　　　　　
Typhoon Department