共查询到20条相似文献,搜索用时 15 毫秒
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L. Stefanutti F. Castagnoli M. Del Guasta M. Morandi V. M. Sacco V. Venturi L. Zuccagnoli J. Kolenda H. Kneipp P. Rairoux B. Stein D. Weidauer J. P. Wolf 《Applied physics. B, Lasers and optics》1992,55(1):13-17
A four wavelength backscattering depolarization LIDAR designed for polar stratospheric cloud and stratospheric aerosol measurement is described. The system uses the following wavelengths: 355 nm, 532 nm, 750 nm, and 850 nm. These wavelengths, obtained by means of the third- and second-harmonic of a Nd: YAG laser and by means of a tunable Ti: Sapphire laser, are chosen in a way to better characterize the particel size of such stratospheric aerosols. They are not emitted simultaneously as the LIDAR system is designed with only two detection channels permitting to detect, in the analog and in the photon counting mode, both the direct and the depolarized backscattered signal. The system has been operational in northern Finland since the end of November 1991. 相似文献
3.
It is the intention of this paper to report on the currently used methods to solve the different LIDAR signal inversion problems for molecular atmospheres, aerosols and clouds. Apart from more traditional approaches, we shall present a recent one using multiple scattering effects rather than avoiding them, which is useful especially for dense clouds. 相似文献
4.
Using the Colorado State Na Lidar, surges of stratospheric aerosols caused by the eruption of Mt. Pinatubo have been observed from August to December 1991 over Fort Collins, CO (40.6° N, 105° W), showing a clear increasing trend in stratospheric aerosol activities. These aerosol layers are characterized by the backscatter-ratio profile at 589 nm for altitudes from 12 km to 40 km.On leave from: Department of Radioelectronics, Peking University, Beijing, P.R. China 相似文献
5.
B. Tatarov T. Trifonov B. Kaprielov I. Kolev 《Applied physics. B, Lasers and optics》2000,71(4):593-600
We report an experimental study of the lidar signal depolarization as a function of the relative contribution of the multiple
scattering in case of optically dense objects in the atmospheric planetary boundary layer. Results of the observation of fog
and stratus clouds are presented, as well as those obtained by sounding of stratocumulus clouds during a snowfall. The lidar
data point to a rise of the depolarization coefficient as the influence of the multiple scattering increases in consequence
of both viewing angle enlargement and penetration into the object sounded. The variations of the depolarization coefficient
are studied as a function of the field of view. In the case of fog, this dependence is approximated by a three-parameter exponential
law; it is found that the depolarization increases steeply when the viewing angle is increased from 9 mrad to 12.5 mrad. The
relationships between the approximation parameters and the microphysical characteristics of the scattering medium are considered.
The experimentally determined size of the area where multiple scattering occurs is in good agreement with that calculated
according to the diffusion model. The results obtained on the multiple scattering effect on the depolarization can also be
employed in determining the extinction coefficient profiles in optically dense objects, as well as in evaluating the characteristic
size of the scattering particles.
Received: 6 September 1999 / Revised version: 7 February 2000 / Published online: 6 September 2000 相似文献
6.
A. Ansmann M. Riebesell U. Wandinger C. Weitkamp E. Voss W. Lahmann W. Michaelis 《Applied physics. B, Lasers and optics》1992,55(1):18-28
A combined Raman elastic-backscatter lidar has been developed. A XeCl excimer laser is used as the radiation source. Inelastic Raman backscatter signals are spectrally separated from the elastic signal with a filter or grating polychromator. Raman channels can be chosen to register signals from CO2, O2, N2, and H2O. Algorithms for the calculation of the water-vapor mixing ratio from the Raman signals and the particle extinction and backscatter coefficients from both elastic and inelastic backscatter signals are given. Nighttime measurements of the vertical humidity distribution up to the tropopause and of particle extinction, backscatter, and lidar ratio profiles in the boundary layer, in high-altitude water and ice clouds, and in the stratospheric aerosol layer are presented. Daytime boundary-layer measurements of moisture and particle extinction are made possible by the improved daylight suppression of the grating polychromator. Test measurements of the CO2 mixing ratio indicate the problems for the Raman lidar technique in monitoring other trace gases than water vapor. 相似文献
7.
Evaluation of dual differential absorption lidar based on Raman-shifted Nd:YAG or KrF laser for tropospheric ozone measurements 总被引:1,自引:0,他引:1
Based on Raman-shifted Nd:YAG or KrF laser, a method of three-wavelength Dual DIfferential Absorption Lidar (DIAL) for tropospheric ozone measurements is proposed. A theoretical analysis and numerical simulations of the measurement error have been performed. The results show that this method can reduce the error in ozone measurements caused by the aerosol layer in the troposphere by a factor of ten. The proposed method is also shown to be insensitive to aerosol optical properties, and therefore, one does not need to know the wavelength dependence of aerosol scattering. The dual-DIAL with 277.1, 291.8, 313.2 nm radiation based on a Raman-shifted KrF laser can be used both during day- and night-time. The dual-DIAL with 289.0, 299.1, 316.1 nm radiation based on Raman-shifted Nd:YAG laser can only be used during night-time. 相似文献
8.
V. M. Sacco F. Castagnoli M. Morandi L. Stefanutti 《Optical and Quantum Electronics》1989,21(3):215-226
An elastic backscattering lidar and initial results are described. The lidar system has been designed to operate in Antarctica for the Italian National Programme for Antarctic Research. The first field trials were held during the period from 31 December 1987 to 10 February 1988. Data were collected for both tropospheric and stratospheric atmospheric parameters. Tropospheric measurements included the cloud base, optical depth, extinction and backscattering coefficients for clouds, whereas aerosols and the molecular atmosphere were monitored in the stratosphere. The lidar system was also tested for the determination of temperature and density in ranges up to 40 km. Preliminary results of the lidar measurements carried out at Terra Nova Bay are presented. The lidar system is composed of a Nd–YAG laser, a Newtonian telescope and two receiving channels with computer-controlled data acquisition and display equipment. The system is operated in a mobile container specifically designed for the Antarctic environment. 相似文献
9.
A Scanning Multi-Axis Differential Optical Absorption Spectroscopy System for Measurement of Tropospheric NO2 in Beijing 总被引:1,自引:0,他引:1
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A scanning multi-axis differential optical absorption spectroscopy (DOAS) system is developed for monitoring tropospheric NO2 abundance. Measurements at different viewing angles near the horizon can be performed sequentially with one telescope collecting scattered sunlight reflected by a moving mirror. Tropospheric NO2 diurnal variations can be derived from slant column densities (SCDs) of different elevation angles. The result from a field campaign in Beijing in summer of 2005 reveals potential possibility for the monitoring of tropospheric NO2 by multi-axis DOAS technique. 相似文献
10.
X. Wang A. Boselli L. D’Avino R. Velotta N. Spinelli P. Bruscaglioni A. Ismaelli G. Zaccanti 《Applied physics. B, Lasers and optics》2005,80(4-5):609-615
A Monte Carlo-based evaluation of the multiple-scattering influence on ground-based Raman lidar measurements is presented.
The lidar returns from cirrus clouds are analyzed in order to evaluate vertical profiles of the extinction and backscattering
coefficients. Results show that for the typical cirrus cloud, the presence of the multiple scattering can lead to an underestimation
of the extinction coefficient by as large as 200% whereas the backscattering coefficient is almost unaffected for the Raman
lidar technique. An algorithm to select one or a set of phase functions which fit to the lidar data is also presented. It
is an iterative procedure based on Monte Carlo scattering simulation. By comparison of the experimental value of the lidar
ratio, corrected for the multiple scattering influence, and the phase function used in the Monte Carlo simulation, one can
determine a suitable phase function. The validity and sensitivity of the algorithm have been demonstrated by applying it to
simulated cases. The application to some real cases indicates that our procedure allows for the establishing of a practical
scattering model for the cirrus clouds. 相似文献
11.
A long-path absorption procedure for the determination of tropospheric OH concentrations is described in detail. Initial measurements using this method were carried out in Frankfurt a. M. By including in the evaluation the visible radiation of a frequencydoubled dye laser used in the measurements, it was possible to mathematically reduce the signal fluctuations caused by the scattering and density fluctuations of tropospheric air. The resulting detection limit was 3×106 OH per cm3. SO2 concentrations which had to be simultaneously determined in order to eliminate an interference effect, could be detected in the range of 1–40 ppb on the absorption path. 相似文献
12.
The procedure of the Florence group for calculation of LIDAR return from clouds is briefly outlined. The results of the particular case chosen for a comparison with other groups are presented. 相似文献
13.
Yibo Jiang Stan P. Sander 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(2):169-179
Light reflected or transmitted by a planetary atmosphere contains information about particles and molecules in the atmosphere. Therefore, accurate modeling of the radiation field may be used to retrieve information on atmospheric composition. In this paper, a multi-layer model for a vertically inhomogeneous atmosphere is implemented by using the doubling-adding method for a plane-parallel atmosphere. By studying the degree of linear polarization of the transmitted and reflected solar light in the Huggins bands, we find significant differences between tropospheric ozone and stratospheric ozone. The effects of tropospheric ozone change on the linear polarization are 10 times more than that of the same amount of stratospheric ozone change. We also show the aerosol effect on the linear polarization, but this effect is wavelength independent as compared to that caused by the tropospheric ozone change. The results provide a theoretical basis for the retrieval of tropospheric ozone from measurement of linear polarization of the scattered sunlight both from the ground and from a satellite. 相似文献
14.
A. Fix M. Wirth A. Meister G. Ehret M. Pesch D. Weidauer 《Applied physics. B, Lasers and optics》2002,75(2-3):153-163
A pulsed optical parametric oscillator (OPO) with intracavity sum frequency mixing was developed generating energies of up
to 16 mJ in the 281–293 nm wavelength range. Both OPO process and sum frequency mixing are pumped by the harmonics of a single,
medium-sized Nd:YAG laser. The system is characterized by a high overall efficiency (∼4% conversion from 1064 nm to the UV),
a very compact set-up and stable and reliable operation. This system was successfully employed to measure tropospheric ozone
using the differential absorption lidar (DIAL) technique and shows much promise as a lidar transmitter in airborne case studies
as well as in unattended lidar systems for long-term monitoring. An unattended ozone profiling system could already be successfully
realized.
Received: 1 April 2002 / Revised version: 30 May 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax: +49-8153/28-1271, E-mail: Andreas.Fix@dlr.de 相似文献
15.
Müller R 《Physical review letters》2003,91(5):058502
Dissociation induced by cosmic rays of chlorofluorocarbons (CFC) and HCl on the surfaces of polar stratospheric clouds (PSC) has been suggested as playing a significant role in causing the ozone hole. However, observed stratospheric CFC distributions are inconsistent with a destruction of CFC on PSC surfaces and no significant correlation exists between ozone levels and cosmic-ray activity inside the polar regions. Model simulations indicate that this mechanism can have only a limited impact on chemical ozone loss and thus on the recovery of stratospheric ozone. 相似文献
16.
Kexin Zhang Wei Li Hans Eide Knut Stamnes 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,103(2):411-423
A simple, yet complete bio-optical model for the inherent optical properties (IOPs) of oceanic waters is developed. This bio-optical model is specifically designed for use in comprehensive, multiple scattering radiative transfer models for the coupled atmosphere-ocean system. Such models can be used to construct next-generation algorithms for simultaneous retrieval of aerosol and marine parameters. The computed remote sensing reflectance Rrs(λ) is validated against field measurements of Rrs(λ) compiled in the SeaBASS data base together with simultaneous chlorophyll concentrations (C) ranging from 0.03 to . This connection between Rrs and C is used to construct a chlorophyll concentration retrieval algorithm that yields reliable results for a large range of chlorophyll concentrations. The overall performance of a MODIS/VIIRS chlorophyll concentration retrieval algorithm is found to be less satisfactory. 相似文献
17.
Jérôme Vidot Olivier Jourdan Frédéric Szczap Vladimir V. Rozanov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(4):586-601
A theoretical sensitivity study of the influence of cirrus cloud properties on tropospheric NO2 columns retrieved from the spaceborne Ozone Monitoring Instrument (OMI) measurements is performed. It is conducted within the framework of the synergetic use of A-Train sensors to derive more representative trace gas products. We aim to study the potential effects of cirrus clouds on tropospheric NO2 retrievals using a retrieval algorithm that, unlike the OMI Standard and DOMINO algorithms, does not correct for the effects of clouds. The sensitivity study is based on the radiative transfer code SCIATRAN that performs both simulations of top of atmosphere (TOA) reflectances as measured by an OMI-like band and tropospheric NO2 column retrievals based on the differential optical absorption spectroscopy (DOAS) method. The results of the sensitivity study show that if a correction for cirrus clouds is not included in our simple retrieval that does not account for clouds in the first place, the tropospheric column can be underestimated by 55%. This underestimation depends strongly on cirrus parameters as, in order of importance, cloud fraction, cloud optical depth, asymmetry factor of cirrus cloud phase function and cloud top height. The perspective of the synergy between OMI and cloud information obtained from cloud-derived products of the A-Train is evaluated in two parts by applying a simple cloud correction scheme based on the independent pixel approximation (IPA). Firstly, we evaluated the tropospheric NO2 column retrievals error caused by uncertainties in cirrus cloud properties. Secondly we studied the influence of subpixel cloud optical depth variability on NO2 retrievals. From our simulations, it is demonstrated that the error will be reduced significantly if the cloud fraction is lower or equal to 0.5. In this case, the cloud fraction and the cloud optical depth must be known within accuracy less than 0.05% and 50%, respectively. The cloud top height and the asymmetry factor must be known within uncertainty of at least 1 km and less than 0.05, respectively. The latter result shows that the uncertainty of the asymmetry factor is a major source of error in the cloud correction for tropospheric NO2 retrieval in the presence of cirrus. 相似文献
18.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1997,57(4):467-476
Numerical studies of a new method for the retrieval of ozone profile information from nadir-observing satellite measurements in the ultraviolet and visible are presented. The method combines information from back scattered radiation in the Hartley band down to the O3 concentration peak, lower atmospheric information from the temperature structure of the Huggins bands, and a constraint on the total column from the Chappuis bands. The Huggins bands' temperature structure provides altitude information on the ozone distribution that includes clear distinction between stratospheric and tropospheric ozone. Studies presented here include dependence of the retrieved O3 profiles on surface albedo, tropospheric aerosol, and tropospheric O3 content for a range of atmospheric conditions. 相似文献
19.
We develop a new method to distinguish structural change of cells based on light scattering and Fourier spectra analysis. The light scattering detection system is composed of a laser source, an optical microscope, a CCD with high resolution and low distortion. After the scattering patterns of cells are recorded by the CCD, the Fourier spectra are obtained by the intensity distribution of scattered light. In the experiment, the change of cell structure is designed by sonication treatment. It is found that different typical peaks can be shown in the Fourier spectra of MCF7 cells with and without sonication treatment, which indicates that this method can be used to distinguish the structural change of cells. 相似文献
20.
We present results of experimental investigations of the signal-polarization characteristics in the case of lidar sounding
during precipitation. We show and discuss the lidar signals and the depolarization profiles along the sounding path for liquid-
and solid-phase precipitation. In the former case we compare the signal characteristics at different degrees of precipitation
rate. In the latter situation, we consider snowfall with particle shape close to that of Chebyshev particles. We also follow
the lidar-signal changes depending on the field-of-view of the receiving optics. The experimental data are compared with results
of theoretical estimates and models concerning the optical and microphysical characteristics of the rain and snow particles.
In the case of liquid-phase precipitation – rain – the observed dependence of the lidar’s signal-polarization structure on
the precipitation intensity has two aspects: on the one hand, the change of the raindrops’ shape, and, on the other, the multiple-scattering
effects. The lidar data demonstrate that the signal depolarization, and, more specifically, its behavior along the sounding
path, can be used as a criterion for the presence of multiple scattering. In the case of a snowfall consisting of Chebyshev
particles, the simultaneous role is evident of two factors influencing the lidar-signal depolarization, namely, the non-spherical
shape of the particles and the multiple-scattering effects. When the scattering takes place off particles with a large size
and a shape strongly differing from spherical, we observed the predominant role of the non-sphericity of the scattering centers
in the signal depolarization.
Received: 6 December 2000 / Revised version: 11 July 2001 / Published online: 19 September 2001 相似文献