As the core component of lidar, APD detector is used to realize photoelectric conversion of laser echo signal. The detector needs to work at a stable temperature to ensure its application performance. A high gain amplifier circuit is designed. The temperature signal is collected by the MCU and the semiconductor refrigerator is controlled. The precision control of the temperature is realized through the PID algorithm. The adjustable high voltage module is integrated, and the APD bias voltage and temperature can be controlled through the serial port of the MCU. Reducing the volume of the APD detector, ensuring the wide temperature range of the detector and improving the integration degree of the 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 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.
Temperature Water Vapor and Aerosols Raman Lidar has been designed for the measurement of atmospheric composition. In order to investigate characteristics of aerosol boundary layer (ABL) height in Beijing, the lidar system had been installed in the University of Chinese academy of sciences from November 2014 to January 2015 (40.41°N, 116.68°E). The data obtained by Raman lidar have been used to derive the ABL height (ABLH) based on the gradient method. A total of 15 days of haze, 27 days of pollution and 24 days of clean occurred through the entire period of observation. On haze, pollution and clean days, the average ABLH were 0.6~0.9 km, 0.9~1.3 km and 1~1.9 km, respectively. In contrast to clean days, haze days have lower ABLH, and gradient changes are faster. The measurement results show the height of ABL has a negative correlation with the concentration of surface PM. The rate of PM concentration variations increase gradually with the height of ABL in clean, pollution and haze days. the atmospheric temperature distribution is relatively stable in two hours. Temperature from 2 to 3 km altitude tends to increase gradually for the observation period.
Wind is one of the most significant parameter in weather forecast and the research of climate.It is essential for the weather forecast seasonally to yearly ,atmospheric dynamics,study of thermodynamics and go into the water, chemistry and aerosol which are have to do with global climate statusto measure three-dimensional troposphericwind field accurately.Structure of the doppler wind lidar system which based on Fabry-Perot etalon is introduced detailedly. In this section,the key parameters of the triple Fabry-Perot etalon are optimized and this is the key point.The results of optimizing etalon are as follows:the FSR is 8GHz,the FWHM is1GHz,3.48 GHz is the separation distance between two edge channels,and the separation distance between locking channel and the left edge channel is 1.16 GHz. In this condition,the sensitivity of wind velocity of Mie scattering and Rayleigh scattering is both 0.70%/(m/s) when the temperature is 255K in the height of 5Km and there is no wind. The simulation to this system states that in±50m/s radial wind speed range, the wind speed bias induced by Mie signal is less than 0.15m/s from 5 to 50km altitude.