In this paper, through the Aerosol-lidar observation data located in the western suburbs of Hefei, a continuous aerosol pollution incident was observed from December 13 to 15, 2018. The range corrected signal and extinction coefficient profile continuously observed through fixed-point observation of ground-based lidar can accurately reflect the aerosol content and the characteristics of aerosol changes. The aerosol is mainly distributed below 1.5km. Through depolarization analysis of aerosol particles, the depolarization ratio is below 0.16, and it is concluded that the aerosol particles are spherical particles with a smaller particle size, and combined with the HYSPLIT model analysis, the main pollutants are transmission and industrial emissions of northern and eastern coastal cities in China.
As one of the effective means of atmospheric detection, lidar is gradually developing towards miniaturization and lightweight. The detection and acquisition system needs to be integrated and optimized. It is necessary to develop a data acquisition system with high cost performance and self-control for the requirements of Lidar industrialization on performance and cost. In this paper, an integrated system of lidar detection and data acquisition (DAQ) is designed by using Field Programmable Gate Array (FPGA). The whole system has many advantages, such as small volume, low cost, convenient adjustment, high adjustment accuracy, convenient acquisition and so on.
Raman-Mie scattering lidar is widely used to monitor atmospheric aerosols, but there are still some errors in the detection of bottom echo signals. Fernald method is one of the most widely used methods to calculate atmospheric aerosols, but it is difficult to determine the atmosphere its boundary value. The boundary value of backscattering coefficient can be calculated better by using scattering method than by iteration method, but there are still some errors. By combining the Fernald method with the optimization of the laser radar constant and the optimization of the iteration algorithm, an optimization method for selecting the calibration value is proposed without loss of accuracy. The new extinction profile is retrieved and its noise is analyzed. The relative error and defects of this method are proposed, which provides a reference for the calculation of extinction coefficient in the future.
A miniaturized, compact lidar data acquisition system based on the heterogeneous multi-core processor ZYNQ was developed to detect aerosol in the atmosphere. This paper introduced system structure of lidar, design method of the embedded program. The data acquisition system consist of ZYNQ processor, analog signal conditioning circuit, analog to digital signal converter with 12-bit resolution ,60 MHz sampling frequency and communication interface, etc. Using the system in combination with 355nm wavelength laser, telescope and other optical module, etc. echo signal of lidar is detected and data is transmitted to the host computer software via Ethernet. Compared with the traditional acquisition card which use Peripheral Component Interconnect (PCI) or PCI express interface communicating with Industrial Personal Computer (IPC), the volume and power consumption are reduced a lot. due to the analog circuit, the control center and the Gigabit Ethernet communication circuit are integrated on one board, the stability of the detection system is also improved, the paper provides a reference design for the miniaturization of the laser radar system.
Mie scattering lidar is widely used in the field of atmospheric detection. Photomultiplier Tube (PMT) module is usually used to collect echo signals. Whether the PMT module can reliably receive and convert backscatter echo signals directly determines the accuracy of lidar inversion data. Conventional plus high-voltage power supply for gain adjustment, there are problems such as inconvenient operation and low adjustment accuracy. In this paper, a gain control system of PMT module based on FPGA is designed for Mie scattering lidar. The host computer sends a specified command to the FPGA according to the communication protocol, and the FPGA driver DAC controls the adjustment of the gain of the PMT module. The experimental results in the Mie scattering lidar system show that the detection system has the advantages of convenience, rapidity, high precision, practicality and reliability.
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