TITLE: Amami Ceilometer data AUTHOR: Toshiyuki Murayama Tokyo University of Mercantile Marine Department of Physics 2-1-6 Ecthujima Koto-ku, Tokyo, JAPAN Tel: +81-3-5245-7464 Fax: +81-3-5245-7339 murayama@ipc.tosho-u.ac.jp 1.0DATA SET OVERVIEW: A ceilometer (Visala CT25K) of Tokyo University of Mercantile Marine was temporally installed at Amami-Ohshima (28.44N, 129.70E), the observation site of APEX-E2. The purpose is to support the flight planning and to obtain the vertical distributions of aerosol and cloud. The data presents the attenuated backscatter coefficient at 905nm from the surface to 7.5km in height. The data were collected continuously from April 13, 2001 08:34 to April 26, 2001, 02:42 UTC. 2.0INSTRUMENT DESCRIPTION: The ceilometer CT25K is manufactured by Visala Oyj (http://www.vaisala.com). The principle of the instrument is lidar using laser diode. The wavelength of the laser diode is 905nm +- 5nm at 25 degree in centigrade. Each measurement was accomplished with 65,536 laser shots within 11.7 seconds. The interval of measurement was set as 15 seconds. A special option, "algorithm scale", was added in this apparatus. Then the backscattter signals were recorded with the resolution 100 times higher than normal model. The range resolutions of reported cloud base and backscatter profile are 15m and 30m, respectively. The maximum detection range is 7.5km. The instrument was inclined with 5 degree to the zenith. 3.0DATA COLLECTION AND PROCESSING: The backscatter record were averaged for 40 profiles, i.e., every 10 minutes, to increase the signal to noise ratio. Because we increased the resolution of record by the algorithm scale, the detection range is limited to 0.032768/km/sr. Then the backscatter signals from low-level clouds and precipitation were often exceeded the range. The instrument was calibrated by the manufacture before the shipping (on Feb. 8, 2001). 4.0DATA FORMAT Data file is tab delimited ASCII file. The data are given in ASCII matrix format. The whole data was separated to two files. The unit of attenuated backscatter coefficient, i.e., no collection of attenuation, is [/km/sr]. The first column indicates the height above AGL in [km], which is corrected for the 5-degree inclination. The first raw indicates the mid-time of averaged profiles in UTC. The second one is the date and time in decimal days of the mid-time. 5.0DATA REMARKS: The signal to noise ratio decreased considerably at high altitudes in the daytime due to the large acceptance of background light. The local time is 9 hour ahead of UTC. 6.0REFERENCES: 1.V. V. Tanner, A. K. Piironen, J. Räsänen, and J. Lönnqvist, "Urban aerosol detection with the vaisala ceilometer", 26-28, 2000, in Symposium on Lidar Atmospheric Monitoring (AMS, Long Beach, California) Acknowledgements The infrastructure, e.g., computer, housing, communication, and the installation were supplied by National Institute of Environmental Studies (PI: Nobuo Sugimoto) and APEX project (PI: Teruyuki Nakajima, CCSR, University of Tokyo).