Precipitation and Cloud

Local Heavy Rainfall

Extreme heavy rainfall is sometimes happening in urban area which may paralyzed the city functions. Especially at noonday in summer season, the cumulonimbus cloud is growing up by the instability air, and the local convection rainfall is happened.

Because of the complex topography in Japan, it is very hard to expound the mechanism so clearly.

In our laboratory, we try to use the statistic way or WRF model to do the numerical simulation to figure out the factor of the phenomena.

Study area:The simulation result of local heavy rainfall used WRF ideal experiment in Kansai region.

Simulated results of 3-hourly accumulated precipitation from the WRF model
Left panel: Control experiment
Center panel: Sensitivity experiment without mountains
Right panel: Sensitivity experiment without ocean.

  • Kuno, Y., H. Kusaka, 2014: Climatological study of the heavy precipitation around the Nobi plain in summer. Tenki, 61(8), 661-667. 2014/08/31(Acknowledgement:RECCA) .
  • Kusaka, H., T. Hanyu, and K. Nawata, 2010: Case study of local heavy rainfall, focusing on GPS precipitable water vapor-rainfall event observed in Tokyo on July 4, 2000-. Geophysical Review of Japan., 83(5), 479-492. 2010/09/01 (Acknowledgement: S5) .

Urban Rainfall

→ Please read Urban Climate page.

Fair Weather Cumulus

Now describing.


 Some areas in Japan are among the most prone to fog formation in the world. In particular, basin fog and sea fog appearing on the Pacific coast are well known. Fog can cause a serious traffic hazard because of poor visibility. On the other hand, fog creates beautiful and fantastic scenery, which can be a tourism resource.

In our laboratory, we mainly focus on fog appearing around Ibaragi Airport and in the Aizu basin. Currently, we investigate the mechanism of fog formation using live-camera image data, the WRF model and LES model.


(1) Fog in the Aizu basin
The Aizu basin is located in the northwestern part of Fukushima Prefecture where fog frequently appears. We have developed a method for predicting fog in this basin, which has higher accuracy than the previous approach.

(2) Fog around Ibaragi Airport
Ibaragi Airport, located about 85 km north of Tokyo in eastern Japan, opened in 2010, where fog frequently appears. We investigate the horizontal distribution of the fog, using a live-camera image data.

(3) Fog in HAKONE

(4) Developing Fog-models

Fog observation around Lake Ashi by the live cameras
Pictures token by Live cameras (Left), in Sunny day (Center), in Fog day (Right)
  • Akimoto,Y., H.Kusaka, 2015: A climatological study of fog in Japan based on event data. Atmos. Res., 151, 200-211. 2015/01/01(Acknowledgement: SOUSEI, RECCA) .