Fine Structure of Vertical Motion in the Stratiform Precipitation Region Observed by a VHF Doppler Radar Installed in Sumatra, Indonesia

Noriyuki Nishi Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan

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Masayuki K. Yamamoto Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan

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Toyoshi Shimomai Interdisciplinary Faculty of Science and Engineering, Shimane University, Shimane, Japan

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Atsushi Hamada Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan

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Shoichiro Fukao Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan

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Abstract

Vertical motion W profiles in the stratiform precipitation region of mesoscale cloud clusters were investigated using wind data observed by VHF Doppler radar installed in western Sumatra Island (0.2°S, 100.32°E). A special mode for W observations was introduced in November 2003, and W data with high accuracy were obtained during most of the period, with fine resolutions of 3 min in time and 150 m in vertical direction. The typical fine structure of W within the nimbostratus in the stratiform precipitation region was investigated by the case study of 6, 8, and 20 November 2003. In the later 2 or 3 h of the stratiform precipitation period, gentle upward motions with small time and height fluctuations were observed over a several-kilometer height range from the middle to upper troposphere. Values of W were weakly positive (0–40 cm s−1) continuously, with little strong upward motion greater than 40 cm s−1 and downward motion.

Corresponding author address: Noriyuki Nishi, Division of Earth and Planetary Science, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake, Sakyo, Kyoto 606-8502, Japan. Email: nishi@kugi.kyoto-u.ac.jp

Abstract

Vertical motion W profiles in the stratiform precipitation region of mesoscale cloud clusters were investigated using wind data observed by VHF Doppler radar installed in western Sumatra Island (0.2°S, 100.32°E). A special mode for W observations was introduced in November 2003, and W data with high accuracy were obtained during most of the period, with fine resolutions of 3 min in time and 150 m in vertical direction. The typical fine structure of W within the nimbostratus in the stratiform precipitation region was investigated by the case study of 6, 8, and 20 November 2003. In the later 2 or 3 h of the stratiform precipitation period, gentle upward motions with small time and height fluctuations were observed over a several-kilometer height range from the middle to upper troposphere. Values of W were weakly positive (0–40 cm s−1) continuously, with little strong upward motion greater than 40 cm s−1 and downward motion.

Corresponding author address: Noriyuki Nishi, Division of Earth and Planetary Science, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake, Sakyo, Kyoto 606-8502, Japan. Email: nishi@kugi.kyoto-u.ac.jp

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