| As an important component of the atmosphere,aerosols have an important influence on the radiation balance of the earth's gas system,atmospheric chemical processes,visibility,gas composition and air quality.Changes in aerosol content are closely related to human life and production.In order to study the properties of aerosols,it is necessary to observe the temporal and spatial distribution of aerosols.LED light source radar atmospheric aerosol detection technology,which has the advantages of LED's rich wavelengths and small blind zone,has important academic significance and scientific research value for studying the optical properties of aerosol at different wavelengths and the content and spatial-temporal distribution of aerosol.Aiming at the demands of atmospheric aerosol detection at different wavelengths of the bottom layer,this thesis proposed and carried out the study of new type of aerosol detection radar techniques based on LED light source.A new pulsed LED remote sensing light source for aerosol detection radar was researched and designed.According to the aerosol Mie scattering remote sensing detection principle,a new single-wavelength radar system based on high-power LED was designed and developed and aerosol night observation experiments and analysis were carried out in Xi'an city.The spatial and temporal distribution profiles of atmospheric aerosols were obtained,verifying the feasibility and detection performance of the LED light source radar system.In order to study the optical properties and microphysical properties of aerosols,a new multi-wavelength radar based on white LED was proposed and developed,and multi-wavelength aerosol observation experiments were carried out at night.The development of the new LED light source radar enriches the existing optical active remote sensing detection technology with pulsed laser as light source,and provides new detection method for the studies of atmospheric environment monitoring and the optical and microphysical properties of aerosol.The research on high-power LED radar detection light source has been carried out.Aiming at the problems of high-power LED as Mie scattering radar's light source,such as continuous illumination and poor collimation,a pulsed constant current source circuit based on MOSFET was designed to obtain the LED pulse beam with peak power of milliwatt level and pulse width of 200ns,which met the requirement of optical radar remote sensing detection;and an optical path combining a total internal reflection collimator and an inverted Kepler telescope structure was designed to control the divergence angle of the LED beam in the range of 11 to 25 mrad.The above works solved the key problems that restricted the application of LED to remote sensing radar,and provided technical support for the study of LED light source radar techniques.According to the aerosol detection principle,a set of new type single-wavelength radar system based on LED light source was designed.The coupling system of radar transmitting and atmospheric echo signal receiving part was mainly designed;under the condition of the large divergence angle(11?25mrad),the geometric overlap factor of the system and the feature of the backscattered light received by the system in near range were analyzed,so that the divergence angle and field of view were optimized,as well as the minimum detection height of the radar system was calculated and analyzed.Using the U.S.standard atmospheric model,the signal-to-noise ratio of the system and the influences of system parameters on the nighttime detection performance of the radar were analyzed.The system parameters were optimized.It is verified that the designed new-type LED remote sensing source can be used for aerosol active remote sensing detection radar and the feasibility of detecting the aerosol by LED light source radar is theoretically verified.A single-wavelength LED light source radar system was developed.It was characterized by a near detection range.According to this feature,the data preprocessing method of echo signal and the inverse algorithm of aerosol extinction coefficient were studied.Using 530nm wavelength radar system,night horizontal observation experiments were carried out to verify the feasibility of the system and the reliability of the experimental results.Further conducting night multi-wavelength vertical observation experiments,the atmospheric echo signals of 475nm,530nm and 625nm wavelengths below 300m height in Xi'an city were obtained for the first time and the vertical distribution profiles of aerosol extinction coefficients at various wavelengths were obtained.The night continuous observation experiments were carried out,and the THI maps of range squared corrected signal and aerosol extinction coefficient at 530nm wavelength were obtained,as well as the continuous change of the low-level atmospheric aerosol content were analyzed.The new aerosol multi-wavelength synchronous detection method based on white LED source radar was proposed and research on fine spectroscopic and signal extraction methods for multi-wavelength spectral signals has been carried out.According to the detection requirements of aerosol microphysical properties,the signals at four wavelengths(450nm,525nm,600nm and 661nm)were splitted by dichroic mirrors and interference filters,which realized the separation and extraction of Mie scattering echo signals in different wavelengths.A multi-wavelength synchronous detection radar system based on white LED was developed and preliminary observation experiments were carried out at night,obtaining the four wavelengths aerosol extinction coefficient profiles below 300m height.The continuous observation experiments were carried out,and the variation of atmospheric aerosol concentration over time were analyzed in detail by the THI map. |
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