Observation and modeling of the Kampachi Cloud (the cloud street over Tokyo in summer)

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Recently, a street of cumulus clouds (the so-called "Kampachi Cloud") was frequently observed over the Metropolitan Loop Road No.8 in Tokyo in summer. The lidar network and airborne observations were carried out at three lidar stations from 1995 to 1997 in order to investigate the mechanism of the Kampachi cloud. The main results are summarized as follows.(1) The analysis of surface wind and temperature distributions in Tokyo revealed that the geographical location of the cloud street was determined by the interaction between the heat island circulation and the land and sea breeze circulation in Tokyo.(2) The lidar network and radiosonde observations of the cloud were carried out in Tokyo in order to investigate the structure of the Kampachi Cloud. A typical cloud street was observed by lidar at 1200m just above the mixed layr in the afternoon on 8 August 1994, when the sea breezes from the Tokyo and Sagami Bays were blowing into the heat island of Tokyo.(3) The airborne observations in 1996 demonstrated that there was the aerosol layr over Tokyo due to the anthropogenic sources. In the daytime, the aerosol layr coincides the mixed layr. The results suggested that the condensation nuclei and water vapor for the Kampachi Cloud street may be supplied from the mixed layr.We proposed an observational model of the atmospheric environment and the Kampachi Cloud over Tokyo. Sea breezes from the Tokyo and Sagami Bays, the heat island along the Loop 8, the aerosol layr and the Kampachi Cloud characterize the atmospheric environment over Tokyo in summer.