Title: INDOEX: Six-wavelength lidar measurements at Hulule Contact: Dietrich Althausen Institute for Tropospheric Research Permoserstr. 15 04318 Leipzig, Germany Phone: +49 341 235 2460 Fax: +49 341 235 2361 Email: dietrich@tropos.de Web: http://www.tropos.de 1. Data Set Overview: The data set contains height profiles of particle backscatter coefficient, particle extinction coefficient and particle lidar ratio at 532 nm derived from the six-wavelength lidar measurements at Hulule (4.1 N, 73.3 E) during INDOEX. Datafiles for 7 days (16.02.,18.02.,04.03.,07.03,16.03.,21.03.,25.03. 1999) are included, which show the typical conditions during the northeast monsoon. There is also included a table with our measurement times. If you wish height profiles from other days, please contact us. 2. Instrumentation and data processing The measurements were realized by using a six-wavelength lidar, which is described in detail by Althausen et al. (2000). Two Nd:YAG and two dye lasers emit laser pulses at 355, 400, 532, 710, 800, and 1064 nm simultanously. The elastically backscattered signals at the six laser wavelengths, and additional the Raman signals of nitrogen at 387 and 607 nm and of water vapor at 660 nm are detected. From these signals height profiles of the particle backscatter coefficient at the six laser wavelengths, and the particle extinction coefficient and the particle lidar ratio at 355 and 532 nm, as well as the water vapor mixing ratio are determined. The Raman-method used to derive the particle extinction coefficient and the particle backscatter coefficient from the Raman signal is described by Ansmann et al. (1990, 1992). The particle extinction coefficients are determined from the nitrogen Raman signals. Because of height uncertainties in the correction for the incomplete overlap between the laser beam and the receiver field of view the particle extinction coefficient is available only for heights above 1000 m. The particle backscatter coefficient is calculated from the ratio of the elastic backscatter signal to the respective nitrogen Raman signal. Here the overlap effect cancels out, and thus allows to retrieve reliable profiles down to the ground. The ratio of the extinction coefficient to the backscatter coefficient yields the lidar ratio, a crucial input parameter in the calculation of the backscatter profile from the elastic backscatter signal using the Klett-method. The Raman lidar signals could be detected only at night and with relatively high integration times of 30-120 minutes. Before signal averaging the signal profiles indicating clouds were removed. The averaged, background corrected profiles were smoothed with window length of 180 m (backscatter coefficient) and 600 m (extinction coefficient). The vertical resolution is a factor of 1.15 higher, because the observations were done under a zenith angle of typically 30 deg. In case of the lidar ratio calculation the backscatter and extinction coefficients were derived with smooth window lengths of 180 m. Then the lidar ratio profiles were smoothed by gliding averages of 600 m. The relative errors of the particle backscatter and extinction coefficients are approximately 5-15% and 10-30%, respectively. Thus the relative errors of the particle lidar ratio is approximately 15-40%. 3. Data Set Description data file structure: ascii file naming convention: ex_bc_lr_yymmdd_ta-te_a.dat (The file contains height profiles of the particle extinction coefficient (ex), particle backscatter coefficient (bc) and particle lidar ratio (lr). yymmdd means the date of the measurement, ta-te means start and end time of the integration interval (UTC), and 'a' means the integration time in min) remarks: All profiles are calculated with the Raman-method for the wavelength 532 nm. 4. References Althausen, D., D. M=FCller, A. Ansmann, U. Wandinger, =20 H. Hube, E. Clauder, and S. Z=F6rner,=20 Scanning six-wavelength eleven-channel aerosol lidar,=20 J. Atmos. Ocean. Tech., 17, 1469-1482, 2000. =20 Ansmann, A., M. Riebell, and C. Weitkamp,=20 Measurement of atmospheric aerosol extinction profiles with a Raman lidar, Opt. Letts., 15, 746-748, 1990. Ansmann, A., U. Wandinger, M. Riebell, C. Weitkamp, and W. Michaelis,=20 Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar,=20 Appl. Opt., 31, 7113-7131, 1992.