Fine structure of vertical motion in the stratiform precipitation region observed by Equatorial Atmospheric Radar (EAR) in Sumatra, Indonesia

Vertical motion (W) profiles in the stratiform precipitation region of three mesoscale cloud clusters were investigated using wind data observed by VHF Doppler radar installed in the western Sumatra Island (0.2S, 100.32E) named EAR. 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 minutes 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 two or three hours 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) continuously, with little strong upward motion greater than 40 cm/s and downward motion.