Measurement of Asian dust in the troposphere have been performed with Mie scattering lidars that are Multi-wavelength aerosol lidar (MWA lidar) and Automatic Continuous operated lidar (ACA lidar) at Suwon, Korea (37.2N-127.6E) in the spring of 2000-2004. These lidar systems are based on pulsed Nd:YAG and multi-receiving channels. It consists in two or three mode that MWA lidar are 355 and 532 nm backscatters and 532nm depolarization ratio, and ACA lidar are 532 and 1064 nm backscatters, 532 nm depolarization ratio, and 1064/532 nm aerosol color ratio. During five years (2000-2004) of intensive observation of Asian dust more than 56 episodes and 2,177 vertical profiles were successfully measured. The significant dust in March 2002 to May 2003 showed the dust layers are located in the altitude range of 0.2-3 km. In this case, the depolarization ratio is large than 15% and in some case up to 30%. The ratio of backscattering ratio and the aerosol color ratio are in teh range of 1-5 and 0.3-0.9 respectively. To identify the Asian dust, we retrieved the particle size distribution from the signals of 355nm and 532nm of MWA lidar. In the 12:35-12:40, March 21, 2000, the composition percentage of particle square distribution spectrum of small particles at 0.069-0.225 μm are higher value from 12-39%. Also large particles is lower that are about 17-19% at 0.752μm, 7% at 1.301 μm, and 5% at 2.355μm, respectively.
The study of backward trajectory carried out in this episode. The results coincide well with the lidar measurement profiles.
We conduct network observations using ground-based Mie-scattering lidars in Asian region in cooperation with various research organizations and Universities. Primary purpose of the network is for studying generation and transport of Asian dust, observing air pollution and biomass burning aerosols for atmospheric environment studies, observing aerosol vertical distribution and temporal variation for atmospheric radiation studies and climatology, and for validation of chemical transport models and satellite remote sensors. At present, lidars are operated continuously at twelve locations in Japan, China, Korea, and Thailand. The lidars used in the network are two-wavelength (532 nm and 1064 nm) Mie-scattering lidars having depolarization measurement function at 532nm. Flashlamp-pumped compact Nd:YAG lasers are used as the light source. We developed a method for estimating the extinction coefficient of non-spherical air-pollution aerosols separately using the depolarization ratio. This method is based on a simple assumption that observed aerosols are external mixture of two types of aerosols, but it is practically very useful especially for inter-comparison with chemical transport models. We also studied a method for characterizing aerosols using the depolarization ratio and the wavelength dependence of the backscatter coefficient. Asian dust phenomena were observed with the network since spring of 2001. The frequency of the occurrence of dust events and the vertical distribution characteristics were analyzed. Also, seasonal and year-to-year variations were analyzed. At the same time, transport of dust and air-pollution aerosols were studied by comparing the temporal variation of lidar profiles with chemical transport model results.
Asian-dust and Cirrus cloud have been measured by Multi-Wavelength aerosol lidar since 2000 and Automatic Controlled Aerosol lidar since 2002 at Suwon (127°E 37°N),Korea. These Lidars are Mie scattering scheme that use 355/532/1064 nm and 532 nm respectively. The vertical profiles of range corrected backscatter intensity and depolarization ratio on 16 days of Asian dust in springtime of 2002 are analyzed for this report. In Suwon, the Asiandust mainly showed at lower troposphere below 3 km but several cases showed in free troposphere of over 4 km. The peak depolarization ratios are in the range of 20-40%. The thickness of dust layer is about 2-2.5 km in case of lower tropospheric measurements. After event ofAsian dust the cirrus clouds are often measured in resemblance to Asian dust at upper troposphere. The maximum upper altitudes are about 8 to 12 km. The clouds falling down to about 3 km were measured which is a higher depolarization ratio of 10-30 %.
Asian dust have been measured by Multiwavelength lidar which supplied with three wavelengths (355, 532 and 1064 nm) laser and multimode receiver system. The system provides three modes of receiving system of Aerosol (355, 532 and 1064 nm), Raman (387, 408 and 355 nm) and Polarization (532 am) measurements. Six cases of Asian dust profiles from 5 km upto 12 km are achieved in spring of 2000. As the results, we can see the backscattering ratio of aerosol and Asian dust shows similar value that is in the range of 1.2 to 3, but the values of depolarization ratio is large that over 15% of Asian dust than below 10% of aerosol. Also, the concentration of large particle size over O.7O7tm is increased when in cases of Asian dust.
Multipass Ti:sapphire amplifier for the light source of DIAL was developed in an angular-multiplexing, and the characteristics of output energy and spectrum was investigated. In the two-stage multipass amplifier, we obtained the maximum output energy of 42 mJ, the amplification gain of 21 dB and the output efficiency of 26% on the wavelength of 790 nm. In the tuning range of 715 approximately 930 nm the spectral linewidth is 0.05 cm-1. The conversion efficiencies of 35% for SHG at 780 nm and 13% for THG at 390 nm are obtained respectively. The continuous tunabilities of 240 approximately 306 nm in UV region and 360 approximately 460 nm in deep-blue region could be achieved.
We have developed an excimer laser of compact coaxial type which the one line cross flow fan is only used. At 1 kHz repetitive operation, the average power of KrF laser is 56 watt. In this paper, the design parameters and CR characteristics are investigated for the attainment of the 1 kHz excimer laser. We have obtained the overall efficiency of 1.2% with KrF laser gas. At this time, CR and the variation of laser output are 2.97, +/- 9%, respectively. Laser gas volume and active volume are 10 liter, 1.8 (H) X 1.2 (W) X 30 (L) equals 64.8, respectively.
Amplification chracteristics of a discharge excited KrF laser with UV-preionized were investigated. The power gain(Iout/Iin) of a single-pass amplifier system were 20, 7 for input intensity of 50 kW, 0.5 MW, respectively. The small signal gain, absorption coefficient, and saturation intensity were calculated by one-dimensional propagation amplifier model. The KrF* formation efficiency, the extraction efficiency, and the power efficiency were also obtained with this numerical model.