This paper designs a style of particle counter which may measure the aerodynamic size and the
scattering intensity of two scattering angles of the aerosol particles. The scattering intensity can also be
calculated from the size and the refractive index according to the Mie theory. When the aerodynamic size is
equal to the optics size approximatively, we can inverse the refractive index of individual aerosol particles by
combining the relative results of the measurements.
Lidar is a powerful tool to monitor the variation of aerosol extinction coefficient profiles in atmospheric boundary layer. PM10, which is most familiar to environmental specialists, is the particle mass concentration whose diameter is not larger than 10μm. In this paper, PM10 profiles, measured by lidar and DA-OPC at Beijing, is given and their variation is discussed.
The measurements of aerosol extinction coefficient profiles and wind vertical structure were conducted by a lidar and a wind profiler respectively at Daxing southern boundary of Beijing in some periods of summer and winter during 2001-2004. The paper will discuss the variation ofaerosol pollutant layer and aerosol particles horizontal transportation by south-north direction at Daxing Beijing.
Raman frequency shifter is a useful method extending laser wavelength the first Stokes of CH4, H2, and D2 pumped by the fourth harmonic of Nd:YAG laser can be used in DIAL measurement of the trace gases. The stability and energy of SRS are related to focal length of lens active gas pressure input energy buffer gas elements and pressure. We detect the stability and energy of the first Stokes line under pure active and mixture with Ar or He. From our experiment the stability of pure CH4, H2 are almost same under different pressure however the stability of pure D2 changes with pressure. The energy conversion efficiency on Si is different among pure gas (CH4, H2, D2). Furthermore the optimal output energy of the first Stokes line of CH4, H2, D2 are got independently at moderate active gas pressure mixing with moderate buffer pressure.
The fourth harmonic (266nm) of a pulsed Nd: YAG laser is used to pump Raman cells filled with D2 and D2/He. The dependences of the energy conversion efficiency of stimulated Raman scattering radiations upon the system parameters such as the pump energy pressure of pure D2 and partial pressure of He in D2/He mixture were experimentally studied. The maximum energy conversion efficiency of the first Stokes radiation (S1, 289.O4nm) reaches 22.1% in D2/He. The conditions to improve the energy conversion efficiency of Si were found. The results have been used to optimize the laser transmitter system for a S02 differential absorption lidar (S02-DIAL).
A measurement experiment of horizontal visibility was conducted by using a micro pulse lidar (MPL) at Hefei Airport during March of 2003. Segment-average method is used for processing the data measured by MPL. A visibility-meter and an OPC were running simultaneously at same site. The results show that the visibility measured by MPL is of a positive correlation with the ones measured simultaneously by a visibility-meter and a negative correlation with the total number of particles measured by OPC which indicates that it is feasible for MPL to measure the visibility.
An iterative algorithm is presented for the determination of the aerosol optical thickness and the water-leaving radiance simultaneously from SeaWiFS measurements which is based on the wavelength relationships among the water-leaving radiance. The pixel which conforms to the wavelength relationships among the water-leaving radiance can be distinguished during the iterative process. The algorithm was used for the retrieval of the aerosol optical thickness and the water-leaving radiance in the Amoy from the SeaWiFS data. The aerosol optical thickness calculated at wavelength of O.55μm is very close to the values from the Sun-photometer measurements.
The 1064nm Doppler wind lidar with a dual Fabry-Perot etalon based on the edge technique has been developed to measure wind profile in the troposphere. The construction of the lidar system is described in the paper. The dual etalon with high-spectral resolution are used to discriminate the Doppler shift from the aerosol backscattering. The accuracy of the lidar system is analyzed and discussed especially for the etalon parameters. The transmittance curve of the etalon is measured and the results show that the standard deviation of the transmittance will cause the velocity error of 0.5m/s. The lidar system is estimated to measure the wind speed up to 10km with the accuracy of less than 2m/s. The preliminary result of the radial velocity measurements has been obtained.
KEYWORDS: Aerosols, Mass attenuation coefficient, LIDAR, Atmospheric particles, Solar radiation, Humidity, Troposphere, Clouds, Information operations, Signal attenuation
A Mie lidar was used to make observation of Asian dust over Hefei (31.90° N, 117.16° E) in the every spring from 1998 through 2004. This paper presents main features of vertical distribution and temporal variation of Asian dust extinction coefficient at 532 nm wavelength during the seven years.
There were two kinds of vertical distributions of Asian dust extinction coefficients. One indicated that the Asian dust particles intruded into the local boundary layer, causing the very thick dust layer with depth of about 3-4 km. The other showed that the Asian dust passed over Hefei area just above the boundary layer. The aerosol extinction coefficients in the elevated dust layer within the middle troposphere from 3 to 6 km were unusual large.
Seasonal average aerosol extinction coefficient profiles showed that larger aerosol extinction coefficients from 1 km to 10 km altitude range were observed in the springtime rather than in any other season.
A new applied differential absorption lidar system for measurement of SO2 and O3 in the lower troposphere is developed. The emission wavelengths 289.04, 288.38 and 299.05 nm are obtained by stimulated Raman shifting of a Nd:YAG laser. The concentrations of SO2 and O3 have been measured quasi-simultaneously by use of the three wavelengths for compensating measurement results each other. The lidar measurements agree with in situ measurements. The measurement errors, which are primarily attributable to statistical error and variations in atmospheric backscattering intensity during the experiment, are discussed.
ABSTRACT
This paper describes one Raman lidar system for measurements of optical parameters for tropospheric aerosol and cirrus at Hefei (31.9 N/117.17 E) station. Typical extinction and backscatter coefficients profiles of tropospheric aerosol and cloud are presented. Many observation cases show the positive relationship between aerosol optical parameters and water vapor distribution. Some aerosol distributions were captured for dust storm by this Raman lidar in the spring of year 2001~2002. Angstrom coefficient profiles of aerosol are derived in the free troposphere by combining two-wavelength Raman-elastic scattering channels, those values indicate smaller for dust aerosols. Optical thickness and scattering ratio profile of cirrus are obtained by this Raman lidar. The values of extinction to backscatter ratios are frequently found between 20 sr and 70 sr for free tropospheric aerosol, but less than 20 sr for cirrus clouds.
AML-1 Mobile Lidar system is the first mobile lidar system developed in China for measuring the polluted particles in atmosphere. This paper gives the basic principle to measure aerosol, and the way to compute the original data. Finally, As an example, it gives some results ofthe aerosol measured in January, 2002 in Beijing.
In this paper L625 UV-DIAL system was described, and ozone measurement method was briefly introduced. Some observation results were presented and discussed. Ozone data were obtained by L625 UV-DIAL system at Hefei for more than two hundred days. The characteristics of ozone vertical profiles are analyzed, its seasonal variation and stratosphere-troposphere exchange process. Two yearly averaged profiles and their standard deviations were presented.
The extinction-to-backscatter ratio, S1, is a crucial parameter for quantitative interpretation of lidar data. A new method will be presented for obtaining aerosol extinction-backscatter-ratio S in the aerosol layer near the ground by using OPC, visibility-meter and particle-monitors. According to the measured data in Beijing during two periods of August of 2001 and January of 2002, the variation of S will be discussed.
A differential absorption mobile lidar system for pollution monitoring for daytime and nighttime operation is described. It allows 3Dmeasurements by using a steering unit, and can measure four kinds of pollutants in atmosphere, Aerosol, so2, NO2, and 03. The lower detection limit ofthe SO2, NO2, 03, is a few ppb. The max. measurement range is about 3 —5 km. This system was developed at the Anhui Institute of Optics and Fine Mechanics, the Academy of Sciences of China. A few examples ofmeasured 03, SO2 , NO2, and aerosols distributions are presented. Keywords: Mobile lidar, differential absorption lidar, aerosols, 502, NO2, 03.
The violent eruption of Philippine volcano Pinatubo in mid June of 1991 caused a serious perturbation on the stratospheric aerosols for a long period. In the paper, we report L625 lidar observational results in the period of 1991 - 1996, including evolution of volcano Pinatubo cloud. The time variation and vertical distribution of the volcanic cloud height, thickness, peak-scattering ratio, and integrated backscattering coefficients will be analyzed. L625 lidar measurement data of stratospheric aerosol reveal the characteristics of background period before the volcanic eruption, the evolution of the Pinatubo volcanic cloud, and present new background level.
This paper systematically discussed the three-wavelength dual differential absorption lidar (dual-DIAL) method for measuring the stratospheric and tropospheric ozone profiles in the presence of high loading or inhomogeneous aerosols along the measurement path. Results of theoretical analysis and comparisons with DIAL and aerosol correction method show that the three-wavelength dual-DIAL method not only can greatly reduce the effect of aerosols on tropospheric and stratospheric ozone measurements, but also can get more accurate ozone profiles than DIAL after aerosol correction. The system error of three-wavelength dual-DIAL due to aerosols is kept in a low level. As the system error in the three-wavelength dual-DIAL is almost insensitive to the spatial inhomogeneity of aerosol loading and aerosol optical properties, this method does not need to known the detailed information about the spatial distribution of aerosol loading and aerosol optical properties. In the regions contained high loading or inhomogeneous aerosols, accurate ozone profile can be obtained directly from the lidar return signals with three wavelengths dual-DIAL method. Experimental results indicate the three wavelengths dual- DIAL method is effective.
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