Nobuo Sugimoto

Algorithm to Retrieve Aerosol Optical Properties From High-Spectral-Resolution Lidar and Polarization Mie-Scattering Lidar Measurements

We developed an algorithm to estimate the vertical profiles of extinction coefficients at 532 nm for three aerosol types that are water-soluble, soot, and dust particles, using the extinction and backscattering coefficients at 532 nm for total aerosols derived from high-spectral-resolution lidar (HSRL) measurements and the receiving signal at 1064 nm and total depolarization ratio at 532 nm measured with Mie scattering lidar (MSL). The mode radii, standard deviations, and refractive indexes for each aerosol component are prescribed by the optical properties of aerosols and clouds database; the optical properties for each aerosol component are computed from Mie theory on the assumption that their particles are spherical and homogeneous, except for dust. To consider the effect of nonsphericity, the dust lidar ratio at 532 nm is assumed to be 50 sr, the value that is reported for Asian dust from the other observational studies. We performed sensitivity study on retrieval errors. The errors in extinction coefficient for each aerosol component were smaller than 30% and 60% when the measurement errors were plusmn5% and plusmn 10%. We demonstrated the ability of the algorithm by applying to the HSRL + MSL data measured at Tsukuba, Japan. Plumes consisting of water-soluble aerosols, soot, dust, or their mixture were retrieved; these results were consistent with simulation with a global aerosol transport model. Introducing the dust lidar ratio significantly improved a correlation between the retrieved dust concentration and the aerosol depolarization ratio at 532 nm derived from HSRL + MSL than the use of spherical dust optical model in the retrieval.

Lidar Network for Monitoring Asian Dust and Air Pollution Aerosols

Network observations of Asian dust and air pollution aerosols are being performed in the East Asian region using automated two-wavelength (1064 nm, 532 nm) polarization (532 nm) lidars. At present, the lidars are continuously operated at 20 locations including cooperative observation sites, in Japan, Korea, China, Mongolia and Thailand. The data from the network are transferred to the data center and processed automatically to derive the extinction coefficients for Asian dust and spherical aerosol. (An iterative backward integration method with an assumption of the lidar ratio and the method using the depolarization ratio for estimating the contributions of non-spherical and spherical aerosols are used in the data processing.) The data from the network are used in various studies including validation/assimilation of dust transport models and the climatological studies of aerosols and clouds.

Multiple scattering simulations for the Japanese space lidar project ELISE

Spaceborne lidar observations have a great potential to improve our knowledge of the atmosphere. However, contrary to ground-based or airborne lidar measurements in observations from space multiple scattering (MS) has to be accounted for under all atmospheric conditions. A simple way to achieve this is to introduce the approximative MS factor F in the single scattering lidar equation. We determined F for measurements of aerosols, ice and water clouds as they were planned with the Japanese space lidar ELISE. We found that F is almost constant in cirrus clouds and in water clouds which are penetrable by lidar. In aerosol layers F depends on penetration depth, extinction coefficient and aerosol type. In comparison to LITE the MS factor is smaller (for aerosols and water clouds) or almost equal (cirrus).

Continuous lidar observations of aerosols and clouds in Tsukuba, Japan and Jakarta, Indonesia

To obtain a observational data set which can be used in the climate studies, the authors are conducting observations with ground based lidars. They started lidar observation with a scanning Mie scattering lidar at NIES in Tsukuba in 1979. They have developed the data analysis method which combines the lidar data and the simultaneous aureolemeter data, and obtained profiles of extinction coefficient of aerosols. This method, however, has a limitation, because it requires an assumption on spatial homogeniety of the optical property of aerosols. The observation, consequently, was limited on the clear days. To improve the frequency of the observation they developed a compact Mie scattering lidar which can be continuously operated. They also developed a high spectral resolution lidar (HSRL) for quantitative measurement of extinction and backscatter coefficients of aerosols and thin clouds. The authors also started observation with a similar Mie lidar in Jakarta in cooperation with Indonesian Institute of Science in 1997. The compact lidar at NIES is a simple vertically looking Mie scattering lidar. It employs a flashlamp pumped second harmonics Nd:YAG laser as a light source. The receiving telescope has a diameter of 35 cm. Photomultiplier tubes are used in the detection system, and the signals are recorded with analog-to-digital converters. Vertical profiles of scattering ratio are indicated for April 20, 1998. A Kosa event was observed on this day. The Mie lidar in Jakarta is a part of the lidar network system for measurement of air pollution in Jakarta.

Lidar method for determination of quartz concentration in the tropospheric mineral aerosols

We present a lidar method that enables the determination of quartz concentration in mineral aerosols. The method combines the Raman scattering lidar using a 466 cm-1 quartz line with a high-spectral resolution lidar (HSRL). The methodology and experimental results are described.

Stratospheric ozone layer observations over tsukuba, Japan by NIES ozone DIAL.

The paper presents results from differential absorption lidar (DIAL) observations of the vertical profiles of ozone, aerosols, and temperature at the National Institute for Environmental Studies (NIES) in Tsukuba (36degN, 140degE), Japan. Currently, the lidar system uses 308/355 nm (DIAL) for lower stratospheric ozone measurements. The 355 nm is also used for aerosol measurements. The lidar system is a part of the International Network for the Detection of Atmospheric Composition Change (NDACC). The version 2 algorithm was used for accurate determination of ozone, aerosols, and temperature profiles. Methods for correcting systematic errors have been applied to the algorithm. Aerosol corrections have been applied to the temperature and ozone calculations. The mean vertical ozone profiles of the NIES ozone lidar were compared with those of SAGE II; they agreed well within a 5% relative difference in the 20- to 40-km altitude range and within 10% up to 45 km. The long-term variations of ozone obtained by the NIES ozone lidar also showed good agreement with those by the ozone sondes and SAGE II at 20 km, 25 km, 30 km, and 35 km. The temperatures retrieved from the NIES ozone lidar and those given by the National Center for Environmental Prediction (NCEP) agreed within 7 (K) in the 35- to 50-km range.

Lidar Methods for Studying Asian Dust Phenomena

Continuous observations of Asian dust are performed with a network of two-wavelength Mie-scattering lidars. The data are used for validation/assimilation of dust transport models. A polarization lidar using two wavelengths, and a Raman lidar detecting quartz contained in dust particles were newly developed for studying characteristics of Asian dust.

A method for estimating mineral dust concentration in aerosol mixture using a polarization lidar

A method using the lidar depolarization ratio for estimating mineral dust concentration in aerosol mixture is described. The method is based on a simple assumption of an external mixture of two types of aerosols with different aerosol depolarization ratio. The method was applied to the lidar data observed in Beijing to estimate contribution of Asian dust in extinction coefficient profiles. The results showed the method is useful for separating contributions of Asian dust and air pollution aerosols. Further conversion to estimate dust mass concentration was tested. The mass/extinction conversion factor determined by the comparison with a high-volume sampler data was 1870 (/spl mu/g/m/sup 3/)/(km) for typical Asian dust in Beijing. The conversion factor is dependent on the particle size distribution and is much smaller for air pollution aerosols.

Development of a two-color dual-polarization pulsed bistatic lidar for measuring water cloud droplet size

A new bistatic lidar is being developed for measuring water cloud particle size. The system employs a pulsed two-color Nd:YAG laser and a receiver with a polarization analyzer located at a suitable scattering angle to measure water cloud droplet size.

Observation of aerosols and clouds planned with the Mission Demonstration Satellite Lidar (ELISE)

The space lidar which is named Experimental Lidar-In-Space Equipment (ELISE) is being developed by the National Space Development Agency of Japan (NASDA) for the Mission Demonstration Satellite II planned for launch in 2002. The primary purpose of ELISE is to demonstrate the space lidar technology and the feasibility of the Mie scattering lidar observation of clouds and aerosols from space. The planned mission period is one year. ELISE is a two-wavelength Mie scattering lidar (1053 nm and 527 nm) using a Nd:YLF laser. The receiver has three detection channels, an analogue channel and a photon counting channel at 1053 nm and a photon counting channel at 527 nm. The planned orbit for ELISE is a polar orbit with an altitude of 550 km. Specifications of ELISE are presented.