Zongming Tao

Measurements of aerosol phase function and vertical backscattering coefficient using a charge-coupled device side-scatter lidar

By using a charge-coupled device (CCD) as the detector, side-scatter lidar has great potential applications in the near range atmospheric detection. A new inversion method is proposed for CCD side-scatter lidar (Clidar) to retrieve aerosol phase function and vertical backscattering coefficient. Case studies show the retrieved results from Clidar are in good agreements with those obtained from other instruments. It indicates that the new proposed inversion method is reliable and feasible and that the Clidar is practicable.

Retrieving aerosol backscattering coefficient for short range lidar using parameter selection at reference point

A new method is proposed based on the analysis of lidar equation which selects aerosol backscatter ratio at a reference point for short range lidar in data processing. Simulation computation and experimental comparison results show that this method is reasonable and feasible. The method is applied to short range lidars, such as atmospheric monitoring lidar-2 (AML-2) and micro-pulse lidar (MPL).

New experimental method for lidar overlap factor using a CCD side-scatter technique

In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter technique using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. A new experiment approach to determine the overlap factor for vertically pointing lidar is presented in this study, which can be applied to Mie lidars. The effect of overlap factor on Mie lidar is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD side-scatter method and Fernald method. This method has been successfully applied to Mie lidar measurements during a routine campaign, and the comparison of experimental results in different atmosphere conditions demonstrated that this method is available in practice.

Cirrus cloud properties measurement using lidar in Beijing

Cirrus cloud has an important effect on the radiation balance between the earth’s surface and the atmosphere. The vertical structures, optical depth and effective lidar ratio of cirrus cloud detected by Mie scattering-polarization-Raman lidar system in Beijing from April 11 to December 31, 2012 are analyzed. The results show that the cloud height in Beijing is lower in spring and higher in autumn, with a mean value of about 8km. The mean of cloud thickness is 0.74km. The mean of optical depth is 0.092, and most observed cirrus cloud is thin while optical depth is less than 0.3. The effective lidar ratio of cirrus is lower in summer and higher in winter, inversely related to local temperature, with a mean value of 32.29Sr.

Software design of control system of CCD side-scatter lidar

Because of the existence of blind zone and transition zone, the application of backscattering lidar in near-ground is limited. The side-scatter lidar equipped with the Charge Coupled Devices (CCD) can separate the transmitting and receiving devices to avoid the impact of the geometric factors which is exited in the backscattering lidar and, detect the more precise near-ground aerosol signals continuously. Theories of CCD side-scatter lidar and the design of control system are introduced. The visible control of laser and CCD and automatic data processing method of the side-scatter lidar are developed by using the software of Visual C #. The results which are compared with the calibration of the atmospheric aerosol lidar data show that signals from the CCD side- scatter lidar are convincible.

A system design of data acquisition and processing for side-scatter lidar

A system for collecting data of Side-Scatter lidar based on Charge Coupled Device (CCD),is designed and implemented. The system of data acquisition is based on Microsoft. Net structure and the language of C# is used to call dynamic link library (DLL) of CCD for realization of the real-time data acquisition and processing. The software stores data as txt file for post data acquisition and analysis. The system has ability to operate CCD device in all-day, automatic, continuous and high frequency data acquisition and processing conditions, which will catch 24-hour information of the atmospheric scatter’s light intensity and retrieve the spatial and temporal properties of aerosol particles. The experimental result shows that the system is convenient to observe the aerosol optical characteristics near surface.

Retrieval method of aerosol extinction coefficient profile by an integral lidar system and case study

Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. But it is difficult to get the full aerosol extinction profile from the ground to the tropopause especially in near ground precisely using backscattering lidar. A combined measurement of side-scattering, backscattering and Raman-scattering lidar is proposed to retrieve the aerosol extinction coefficient profile from the surface to the tropopause which covered a dynamic range of 5 orders. The side-scattering technique solves the dead zone and the overlap problem caused by the traditional lidar in the near range. Using the Raman-scattering the aerosol lidar ratio (extinction to backscatter ratio) can be obtained. The cases studies in this paper show the proposed method is reasonable and feasible.

Properties of cirrus cloud by a three wavelength Raman Mie Polarization lidar: observation and model match

A three-wavelength Raman Mie Polarization Lidar has been developed for cloud and aerosol optical properties measurement. The Nd-YAG laser is employed as emitting source and six channels are used for detecting back-scattering signals from atmosphere aerosol and cloud including 1064 and 355 nm Mie, 607 and 386 nm N2 Raman, two 532 nm Orthogonal Polarization channels. The measured data are used for investigating the cirrus properties including cloud optical depth, polarization ratio, color ratio and lidar ratio. And these results are matched with the microphysical model suggested.

Study of the first Stokes line of Raman cell full of CH4, H2, D2 and their mixture with Ar,He gases

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.

Mobile lidar for measurements of SO2 and O3 in the low troposphere

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.