We performed synergy observation of subvisual cirrus clouds (SVC) with 1064-nm lidar, 95-GHz cloud radar and radiosondes launched every 3 hours at 2¿N, 138¿E for one month from 9 November to 9 December 2001. The estimated effective radius reff of SVC is 9--16 ¿m (5--9 ¿m in mode radius). This assumes that the shape of cloud particles is spherical and the number concentration of the particles is 105 m-3. SVC disappear when temperature anomalies exceed +1.5¿C. The fall velocity of SVC is same as the downward velocity of the phase propagation of the Kelvin wave, and the terminal velocity of hexagonal particles. Thus sedimentation and phase propagation are important for dissipation of SVC. In addition, it was noted that SVC tended to disappear at midday during the observational period except on 27 November 2001.