Reconstruction of aerosol microphysical properties sometimes is like an art. With the lack of complete information about EM wave scattering on particles, we have to use some approximations. This is especially important in lidar sounding of the atmosphere. Aerosol scattering properties depends on complex refractive index of scattering medium, incident wavelengths, aerosol size distribution, scattering angle. On practice we only have backscattering signal at some wavelengths at backscattering. In this paper, we consider a new approach to processing active remote sensing data, which allows us to estimate the concentration of particles, as well as to estimate the most likely values of the complex refractive index. This approach is based on the further development of the Umov effect.
This document presents the results of the study of condesation grows of atmospheric aerosol. We analyze effect of aerosol effective radius changes versus relative humidity. In our experiment we suppose that aerosol has same type (refractive index) during the measurements. We consider different scatterplots Ref f vs RH, β vs RH and α vs RH inside planetary boundary layer and estimate humidification factor. From the experiment we found that: 1) the radius of the particles grows with the index k = 0.484 in accordance with formula (10); 2) an increase in the backscattering coefficients at wavelengths of 355 nm and 532 nm is described by formula (11) and γ = 0.694 and γ= 0.585, respectively. Trend of particulate depolarization ratio as a function of relative humidity corresponds to Case II of Continental Clean atmospere model where water soluble particles has spherical shape.
The dependences of the intensity of sodium emission lines on the time delay during filamentation of laser radiation of femtosecond duration in an aqueous aerosol with large (10 μm) and small (0.8-2 μm) particles was obtained. Emission lines (588.99 and 589.59 nm) were excited by filamentation of femtosecond laser pulses (60 fs, 800 nm, 3.8 mJ) in the weak focus mode with the lens with 500 mm focal length in the Na aqueous aerosol. It was experimentally established the optimal time delay for recording of the emission spectra of the filament in an aqueous aerosol with respect to the laser pulse.
The opportunities of the filament - induced emission spectroscopy method for analysis of elemental composition of aqueous aerosols in the atmosphere are estimated. Emission lines of chemical elements were excited by filamentation of femtosecond laser pulses (60 fs, 800 nm, 4.4 mJ) in the weak focus mode with the lens with 500 mm focal length in the aqueous aerosol. The limits of detection of aluminum, barium, and sodium in the aqueous aerosol are obtained.
The compact mobile hardware-software complex based on a remotely operated vehicle (ROV) and a laser-induced breakdown spectrometer (LIBS) has been developed and tested in laboratory and in real-time condition for the tasks of analyzing the composition of sea water and bottom sediments on the continental shelf.
The spectral and temporal characteristics of plasma radiation generated by a Ti:Sa femtosecond laser pulses on the surface of Ca aqueous solutions are investigated. Optimum parameters of laser radiation and signal registration are determined to improve the metrological characteristics of time-resolved femtosecond laser induced breakdown spectroscopy.
Experimental studies have been carried out to determine the limits of the detection of chemical elements (manganese, magnesium, lead, strontium) in water, when plasma generated by femtosecond laser pulses on the aqueous solutions surface, depending on the parameters of laser radiation (pulse duration, energy and the mode of focusing). The emission lines of chemical elements in plasma generated in a aqueous solution by Ti-Sapphire laser complex at a central wavelength of 800 nm, using focusing lenses with different focal lengths, and also for collimated beams under laboratory conditions are registered.
The results of variations in the microphysical and optical characteristics of atmospheric aerosol in the transition zone "land-ocean" in the Far Eastern region, Primorsky Kray, Vladivostok are analyzed. The data of measurements for the period from 21.02.2016 to 08.12.2017 are analyzed. The values of the height of the planetary boundary layer (PBL) characteristic for the region were obtained. The average value of the height of PBL for 2016 was (2605±532) m, for 2017 (2501±435) m. Seasonal changes in the height of PBL were considered and an insignificant decrease in the height of the PBL in the spring and autumn of 2017 compared with the same period in 2016, the difference was about 300 m. The values of the real and imaginary part of the refractive index of atmospheric aerosol were obtained for the period from 2016 to 2017. The predominance of an aerosol with a small value (about 1.31-1.36) of the actual part of the refractive index for 2016 compared with 2017 is noted. There are particles of large volumes (17 μm3) for altitudes up to 1 km in 2016 compared to 2017 (11 μm3). The values of the atmosphere optical depth for an altitude of up to 3 km for wavelengths of 355 nm and 532 nm are calculated. It is established that the maximum optical depth acquires in the spring period and reaches to 1.15 for a wavelength of 355 nm and to 0.51 for a wavelength of 532 nm.
The spectral and temporal characteristics of plasma radiation (contours and kinetics of the intensity of spectral lines) generated by a Ti:Sa femtosecond laser pulses on the surface of water solutions are investigated. The best parameters of optical spectra registration and of the laser radiation are determined to improve the metrological characteristics of timeresolved femtosecond laser induced breakdown spectroscopy.
The results of lidar sensing of the atmosphere in the continent-ocean transition zone obtained on three modifications of a femtosecond lidar: elastic scattering lidar, Raman lidar, white light lidar are discussed. In the mode of multi-frequency sensing (supercontinuum from the fundamental harmonic), the emission lines of the first positive system of the nitrogen molecule are registered. Comparisons of obtained data with the results of lidar sensing using of nanosecond laser pulses are presented.
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