TITLE: TUMM/Tokyo lidar data (Updated on 13 May 2002) 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 1.0 DATA SET OVERVIEW: Ground-based lidar observation of aerosols by Aerosol lidar Currently, we intend to submit all profiles of normalized backscatter signal, depolarization ratio, and derived extinction coefficient at 532nm during March, April and May in 2001 by separating the data sets for few to several days. Tokyo University of Mercantile Marine is located at Tokyo Bay area influenced by urban and marine environments (35.66N, 139.38E). Reference web page is http://info.nies.go.jp:8094/AsiaNet/tumm/home/tumm/index.html. Detailed observed time is found in the lidar inventory in ACE-Asia data archive. 2.0 INSTRUMENT DESCRIPTION: TUMM aerosol lidar is based on Nd:YAG Q-SW laser. The observation wavelengths are 532 and 1064nm. Depolarization ratio, which is a good measure of non-sphericity of aerosol and useful for detection of mineral dust, was obtained at 532nm. The lidar receivers are composed from three telescopes, and those have different functions. Two receivers (near and far-range one) are used for 532nm polarization-diverse channels to obtain the profiles of backscattering signal and depolarization ratio as low as possible without the correction of overlapping factor between the laser beam and the field-of-view of telescope. The laser pulse power except Raman lidar mode was 20mJ at 532nm. The repetition rate was 10Hz. The laser beam is deflected to vertically. The lidar signals detected by the photo-multipliers (PMTs) were recorded in analog mode with 12-bit lidar transient recorders by Licel (http://www.licel.com) and 8-bit digital oscilloscopes by LeCroy for far and near-range channels, respectively. We relay on the high resolution data obtained by Licel transient recorders, TR40-160. 3.0 DATA COLLECTION AND PROCESSING: The lidar were started and stopped by manually. Normally the data were averaged for 4094 shots, namely every about 7minutes including the data transfer time. The range resolutions of recorded signals were 7.5m (50ns) or 6.0m (40ns). The lidar profiles are obtained by combining two (or three in normalized backscatter signal) receivers' signals from 0.2km to 15km without corrections of the overlapping factor. Using the inversion method developed by Fernald (1984), we retrieved extinction coefficients of aerosol. The range resolution of original lidar profiles were reduced to 30m to increase the signal to noise ratio. Firstly, we find the matching height (typically around 9km under clear condition) with Rayleigh scattering by air molecules by using the atmospheric air density obtained from routine radiosonde data (00 and 12UTC) Tateno (36.05N, 140.13E). By setting the scattering ratio (total to molecular) as 1.00-1.05 at the matching height and assuming the constant lidar ratio in daily, we derived the extinction coefficients with the Fernald's scheme in backward and forward (if necessary). In this processing, we applied the smoothing for the normalized backscatter signals with a window of 150m or 90m above 4 or 6km. The constant lidar ratio, which ranged from 40 to 70 sr, was determined from the comparison with sun-photometer derived optical depth at 532nm. Sun/sky photometer measurements were simultaneously done with the lidar measurement. When such comparison could not been made, we used the lidar ratio of 45sr. Estimated uncertainty of thus derived extinction coefficient is less than +/-25%. The smaller extinction values tend to have more errors. In case of the depolarization ratio, the relative error and the offset error ranges are approximately about +/-5% and 1%, respectively. The depolarization ratios at high altitudes in the daytime or above cloud signals have poor signal to noise ratio (not usable). Some more information is provided in the header of the data files. 4.0 DATA FORMAT Data file is tab delimited text file. The data are given in ASCII matrix format in the coordinates of time and altitude. These are easily read by Microsoft EXCEL. 1st period: April 2-6, 2001 2nd period: April 8-10, 2001 3rd period: April 11-16, 2001 4th period: April 17-19, 2001 5th period: April 20-23, 2001 -99 unavailable data, removed 5.0 DATA REMARKS: Normalized backscatter is the normalized backscattering light intensity by range, laser power and PMT gain. The gain ratios of P- and S-channels in polarization-diverse channels are regularly calibrated. In the connections of lidar signals, the depolarization ratios are connected at 0.6km in range but the normalized backscatter is connected at arbitrary heights depending on the matching conditions. 6.0 REFERENCES: 1. T. Murayama, H. Okamoto, N. Kaneyasu, H. Kamataki, "Application of lidar depolarization measurement in the atmospheric boundary layer: Effects of dust and sea-salt particles", J. Geophys. Res., 104, D24, 31781-31792, 1999. 2. T. Murayama, N. Sugimoto, I. Uno, K. Kinoshita, K. Aoki, N. Hagiwara, Z. Liu, I. Matsui, T. Sakai, T. Shibata, K. Arao, B.-J. Sohn, J.-G. Won, S.-C. Yoon, T. Li, J. Zhou, H. Hu, M. Abo, K. Iokibe, R. Koga, and Y. Iwasaka, "Ground-based network observation of Asian dust events of April 1998 in east Asia", J. Geophys. Res., 106, D16, 18345-18359, 2001. 3. F.G. Fernald, "Analysis of atmospheric lidar observations: some comments", Appl. Opt., 23, 652-653, 1984.