Research Topics in Typhoon Research Department

Study of typhoon prediction using a numerical model ( 1st laboratory )

Numerical simulation of a typhoon

Using a numerical model, we challenge clarification of generation, development, decay, and translation of typhoons for the purpose of improvement of typhoon forecasting. Elaborated numerical model expressed every cloud in the atmosphere enables to simulate a realistic typhoon shown in the figure. This study is not only helped to understand complicate mechanism of the typhoon but also leads to improve numerical prediction such as track, intensity, heavy rainfall, and gust.

(Figure) Cumulative cloud water [0.1kg/m2] of a simulated typhoon in the numerical experiment. Warm color indicates a large amount of cloud. The figure represents eyewall around the center of the typhoon and spiral bands outside the eyewall.

Typhoon-ocean interaction

Strong wind by a typhoon stirs and cools underlying sea water at the upper layer. Sea surface cooling is helped to decrease evaporation, which is a egergy source of typhoons, because evaporation suppresses from the ocean to the atmosphere. This is the reason why sea surface cooling should be accurately predicted in the typhoon intensity prediction. We developed a mixed-layer ocean model to predict sea surface cooling by typhoons. We further develop a typhoon-ocean coupld model to improve the intensity prediction.

(Figure) Sea surface temperature (℃) on August 31 in 1998 simulated in a mixed-layer ocean model. The circle indicates a position of Typhoon No.4 in 1998 every 6 hours. In the slow translation, sea surface cooling is greatly enhanced to sustain high wind at the same area.

Development of storm surge model including the effect of ocean waves.

Typhoon research department challenged studies of disasters concerning typhoons. We have developed a storm surge model for three yreas during 1993-1995. This model has been operationally run in Japan Meteorological Agency. However, it is necessary to install the effect of ocean waves to the storm surge model for the purpose of improvement of storm surge prediction at the coastal ocean like isolated islands and peninsulas.

　A renewal 3-dimensional storm surge model incorporated of the effect of ocean waves has been developed. Using the model, numerical simulation od storm surge was conducted. An enhanced storm surge under the influence of ocean wave was occurred at Hichijo-jima by typhoon No. 3 in 2000. The figure shows observation at Yaene(blue） and result of the numerical experiment(red）. The computed deviation from the astronomical level is improved from the previous model （yellow）in the renewal storm surge model with the effect of ocean waves.

(Figure) The storm surge deviation (cm) from the astronomical level at Yaene from 6 July to 7 July in 2000. The line with dots indicates tidal observation. The broken line indicates the result of previous model. The line indicates the result of renewal model with the effect of ocean waves.

Study of structual change of typhoons using remote sensing data. (2nd laboratory)

Utilization of satellite data to typhoon prediction

Because observation is insufficient to grasp a typhoon and its environment and to predict the typhoon, Remote sensing data, meteorological satellite data, is absolutely imperative. We have studied a methodology of structure of typhoons and environmental atmospheric and oceanic conditions, which contributes to the improvement of typhoon prediction.

(Figure) Information of sea surface wind within Typhoon and Hurricane will be increasingly required for studies using numerical models and disaster prevention. Microwave scatterometer of QuikSCAT, which is on board low orbital satellite, can provide information of the sea surface wind very precisely although we can get the data only twice a day. To utilize less QuikSCAT data more efficient, we have challenged new progressive method in retrieving the sea surface wind from another satellite observations.
Pictures shown above is one of the examples. We have developed a new algorithm in which sea surface wind is estimated from vertical profiles of atmospheric temperature obtained from Advanced Microwave Sounding Unit (AMSU) on meteorological satellite of NOAA. >From the validation in the case of Hurricane Floyd, estimated wind distribution by the algorithm using AMSU data is almost comparable to the wind distribution by QuikSCAT.

Report of Conferrence and Meeting

Other departments