- Meteorological Society of Japan
- Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)
To elucidate the formation of a localized rainfall on a basin with heat and aridity under weak synoptic disturbance in summer, the characteristics of atmospheric conditions on the Kofu Basin preceding the appearance of primary precipitating cells were described from 23 localized rainfall events on the Kofu Basin on days of weak synoptic disturbance at the surface from 1 June to 30 September in 2012 to 2014. Furthermore, using the case study conducted on 25 July 2014, the formation of the atmospheric conditions was described from the standpoint of moisture behavior.
Owing to the thermal contrast between the Kofu Basin with heat and aridity and the outside environment, the south-component wind blowing in the valley connecting it to the coastal region of Suruga Bay and the east-component wind blowing in the valley connecting it to the Kanto Plain entered the Kofu Basin as southwesterly wind and southeasterly wind, respectively, which caused an increase in the water vapor mixing ratio and a slight decrease in temperature at the surface. After that, the amount of precipitable water vapor derived by the global navigation satellite system observation (GNSS-PWV) at Nakamichi in the central region of the Kofu Basin increased abruptly after the moderate increase in GNSS-PWV at all the observation points on the Kofu Basin. Finally, a cloud appeared over the local region between the southwesterly wind and the southeasterly wind; the precipitating cells appeared here at 3.25 to 6.25 km above sea level.
From the above results, the moisture transport to the Kofu Basin, the moisture concentration in the local region, and the appearance of precipitating cells were discussed as the formation of atmospheric conditions leading to a localized rainfall on a basin with heat and aridity.