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Earth Planets Space, Vol. 56 (No. 2), pp. 259-268, 2004

Fog observations with a millimeter-wave scanning radar at Miyoshi basin, Japan

Michihiro Teshiba1, Hiroyuki Hashiguchi1, Akihisa Uematsu1, Hisamichi Tanaka2, Yasunobu Ohmori2, and Shoichiro Fukao1

1Radio Science Center for Space and Atmosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
2Communication Systems Center, Mitsubishi Electric Corporation 8-1-1 Tsukaguchi-honmachi, Amagasaki 661-8661, Japan

(Received September 8, 2003; Revised February 24, 2004; Accepted February 24, 2004)

Abstract: A special fog observation campaign was conducted in the Miyoshi basin, Hiroshima prefecture, Japan during the period November 7-15, 2000. We observed the spatial distributions of fogs and their movements using a millimeter-wave scanning radar. This is the first time that the distribution of basin fogs associated with fog development and decay processes has been examined. Echo intensity observed with the radar, which is mainly associated with fog particle size, was almost under -23 dBZ at levels below 200 m in height. The horizontal distribution of echo intensity changed with time. Namely, weak echoes were observed over nearly all observation areas at first, and then the echoes gradually became stronger as the fogs developed, although the echoes were weaker at higher levels. After sunrise, the echoes decayed. During the developing periods, the occurrence ratio of the echo intensity between -38 and -23 dBZ increased from the lower height, while the ratio decreased from the higher levels during the decay periods. This feature in the developing period is consistent with the results of optical measurements but the feature in the decaying period is inconsistent. It is suggested that this inconsistency is due to the difference in sensitivity between the two measurement approaches.
Key words: Fog, remote sensing, millimeter-wave radar, mesoscale meteorology, boundary layer meteorology.


Corresponding author E-mail: teshiba@kurasc.kyoto-u.ac.jp


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