Project Subjects
Severe Storm Prediction and Impact Assessment ofElectric Facilities Under Global Warming
Background and Objective
In recent years, meteorological disasters by rain storms and the heavy snows happen frequently, and its
relationship with global warming has been pointed out. The inﬂuence of the global warming might be graduallyactualized in 20 or 30 years in the future, and there is a possibility to affect electric power industries in Japan.
One purpose of this study is to improve the accuracy of the numerical weather prediction model for assisting themaintenance and operation of electric power facilities, such as delivery equipment and water power dam. The
second purpose is to predict the climate change over Japan by using the improved forecast model, and to make anassessment of the climate change effect on the electric power equipment.

Main results
1. Research on climate change prediction over Japan due to global warming.
We have developed the numerical weather forecast and analysis system (NuWFAS) to predict severe
storms with the resolution of 3 or 5km. The numerical model of the system has been improved for evaluating soil
water contents, soil temperature, and sea ice, which have an effect on the accuracy of weather and climate simulations. We evaluate the performance of the system from one year long-term simulation (Fig. 1) [N09024]. For thenext step, long-term simulation for the climate change prediction will be carried out.
2. Research on the climate change prediction of ocean currents and waves around JapanWe developed regional ocean current model and ocean wave model for the short range forecast of storm
surges and the near future assessment of that on the climate change. These models were applied to Japan Sea inDec 2005, and are compared with the observed time series of signiﬁcant wave height and sea surface elevation.
The model outputs agreed with observations induced by the storms, although the model could not calculate thesea level for the descending period at some observation points due to lack of information of eddies propagatingfrom the outside of the boundaries (Fig. 2).
3. Research on the improvements of the weather forecast and analysis
To evaluate wind gust intensity, which is very important for wind load design of transmission lines,
we developed the numerical model. As usual, it is very difﬁcult to estimate the intensity of wind gusts throughmeteorological models using coarse grids. However, we show that the Large Eddy Simulation (LES) model withthe grid scale of 50m can capture wind gust features observed in the ﬁeld (Fig. 3) [N09010].
In order to improve accuracy of heavy rain and snow amounts, we investigate the cloud micro physics
in NuWFAS. The models with different cloud micro physics were applied to typhoons, heavy rain events, andcyclones in winter, and were compared with observations. We settled the dual polarization Doppler radar at
Abiko, and observed heavy rain and snow due to thunderstorms, typhoons, and tornados (Fig. 4). These observed
data and cloud micro physics information will be used for the data assimilation model developed in this study.

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Environmental and Energy Utilization Technology

Snow Depth（cm）

120
90
60
30

Observation
NuWFAS0
2008/12/1

2008/12/16

2009/1/1

2009/1/16

2009/2/1

2009/2/16

2009/3/1

Fig. 1 Snow depth comparison
Snow depth results from NuWFAS were compared with the observational data at the National Agricultural Research Center in Hokkaido,
Japan. The results are in good agreement with the observations.

Wind direction →(a) Large-eddy simulation

Wind direction →(b) conventional simulation

Fig. 3 Comparison of surface wind predictions（area:6km×6km ）A large-eddy simulation has a capability to capture stream-wise streaky
structures with low speed ﬂuid motions, which is the source of wind
gusts (“kaze no iki”), whereas predictions with conventional simulations show only mere disturbed wind ﬁelds.

Fig. 2 The comparison of the simulated
and measured water surface elevation at the ﬁve stations (Sado, Noto,Toyama, Maizuru and Hamada)around Japan Sea in Dec. 2005.
The black line is the observation by JMA which has
been removed is periodical astronomical tide. The
red and blue lines are the simulation results driven
by the atmospheric data from NuWFAS model andJMA, respectively. The calculated magnitude andoccurrence time of peak surge agreed with the measurements, although the model could not reproduce
the sea level for the descending period at some stations.

Fig. 4 Images of data observed by our polarimetric Doppler radar(Observation range is 60 kilometers; Left: ｒadar reﬂectivity factor, Right: differential propagation phase)
Precipitation amount is estimated from radar reﬂectivity factor in the conventional radar system. Such a method, however,can lead to a difﬁculty that the accuracy of estimation degrades largely in areas (circled in Fig. 4) far beyond heavy rainfall,because of severe attenuation of radio waves. Polarimetric radar can radiate and receive both horizontally- and verticallypolarized radio waves. Differential phase between waves is not affected by the attenuation effect, so that the accuracy ofprecipitation estimation based on differential phase is expected to be better than the conventional method.

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