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Journal ArticleDOI

Bistatic LIDAR: A Tool for Characterizing Atmospheric Particulates: Part I---The Remote Sensing Problem

TL;DR: In this article, the bistatic, light detection and ranging, LIDAR technique for sensing atmospheric particulates is outlined, and analytical formulations are presented for characterizing both the intensity and polarization of the Bistatic signals.
Abstract: The bistatic, Light Detection And Ranging, LIDAR technique for sensing atmospheric particulates is outlined, and analytical formulations are presented for characterizing both the intensity and polarization of the bistatic signals. Methods are presented on how to handle the remote sensing problem of extracting the particulate angular scattering parameters from the bistatic measurements. Examples are also presented which demonstrate that these methods can be practically applied at least for atmospheric conditions typical of Tucson, AZ.
Citations
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Journal ArticleDOI
01 Mar 1989
TL;DR: In this paper, the development and application of lidar as a tool for remote sensing of atmospheric aerosols and clouds are reviewed, and various approaches for solving the lidar equation to retrieve aerosol properties are summarized.
Abstract: Advances in the development and application of lidar as a tool for the remote sensing of atmospheric aerosols and clouds are reviewed. The lidar sensing technique is described, and various approaches for solving the lidar equation to retrieve aerosol properties are summarized. Examples are presented of lidar applications of aerosol and cloud sensing in both the troposphere and stratosphere. These include environmental monitoring, atmospheric boundary layer studies, retrieval of aerosol optical and physical properties, sensing of clouds, and investigation of volcanic effects in the stratosphere. Comments are offered regarding the future outlook for aerosol and cloud sensing by both ground-based and spaceborne lidar. >

80 citations

Journal ArticleDOI
TL;DR: A CCD-based bistatic lidar system has been developed and constructed to measure scattering in the atmospheric boundary layer and Observations at Mauna Loa Observatory, Hawaii, show excellent agreement with the modeled molecular-scattering signal.
Abstract: A CCD-based bistatic lidar (CLidar) system has been developed and constructed to measure scattering in the atmospheric boundary layer. The system uses a CCD camera, wide-angle optics, and a laser. Imaging a vertical laser beam from the side allows high-altitude resolution in the boundary layer all the way to the ground. The dynamic range needed for the molecular signal is several orders of magnitude in the standard monostatic method, but only approximately 1 order of magnitude with the CLidar method. Other advantages of the Clidar method include low cost and simplicity. Observations at Mauna Loa Observatory, Hawaii, show excellent agreement with the modeled molecular-scattering signal. The scattering depends on angle (altitude) and the polarization plane of the laser.

68 citations

Journal ArticleDOI
TL;DR: Atmospheric aerosols have been profiled using a simple, imaging, bistatic lidar system and the results build on earlier work that compared purely molecular scattered light to theory, and detail instrument improvements.
Abstract: Atmospheric aerosols have been profiled using a simple, imaging, bistatic lidar system. A vertical laser beam is imaged onto a charge-coupled-device camera from the ground to the zenith with a wide-angle lens (CLidar). The altitudes are derived geometrically from the position of the camera and laser with submeter resolution near the ground. The system requires no overlap correction needed in monostatic lidar systems and needs a much smaller dynamic range. Nighttime measurements of both molecular and aerosol scattering were made at Mauna Loa Observatory. The CLidar aerosol total scatter compares very well with a nephelometer measuring at 10 m above the ground. The results build on earlier work that compared purely molecular scattered light to theory, and detail instrument improvements.

62 citations

Journal ArticleDOI
TL;DR: It is concluded that for an accurate estimate of black-carbon radiative forcing, one must take into account the complex morphologies of carbonaceous aerosols in remote sensing studies as well as in atmospheric radiation computations.
Abstract: This paper provides a thorough modeling-based overview of the scattering and radiative properties of a wide variety of morphologically complex carbonaceous aerosols. Using the numerically-exact superposition T-matrix method, we examine the absorption enhancement, absorption Angstroem exponent (AAE), backscattering linear depolarization ratio (LDR), and scattering matrix elements of black-carbon aerosols with 11 different model morphologies ranging from bare soot to completely embedded soot-sulfate and soot-brown carbon mixtures. Our size-averaged results show that fluffy soot particles absorb more light than compact bare-soot clusters. For the same amount of absorbing material, the absorption cross section of internally mixed soot can be more than twice that of bare soot. Absorption increases as soot accumulates more coating material and can become saturated. The absorption enhancement is affected by particle size, morphology, wavelength, and the amount of coating. We refute the conventional belief that all carbonaceous aerosols have AAEs close to 1.0. Although LDRs caused by bare soot and certain carbonaceous particles are rather weak, LDRs generated by other soot-containing aerosols can reproduce strong depolarization measured by Burton et al. for aged smoke. We demonstrate that multi-wavelength LDR measurements can be used to identify the presence of morphologically complex carbonaceous particles, although additional observations can be needed for full characterization. Our results show that optical constants of the host/coating material can significantly influence the scattering and absorption properties of soot-containing aerosols to the extent of changing the sign of linear polarization. We conclude that for an accurate estimate of black-carbon radiative forcing, one must take into account the complex morphologies of carbonaceous aerosols in remote sensing studies as well as in atmospheric radiation computations.

57 citations

Journal ArticleDOI
TL;DR: In this paper, the backscattering coefficient from a slab of thin randomly oriented dielectric discs over a flat lossy ground is used to reconstruct the inclination angle and area distributions of the discs.
Abstract: The backscattering coefficient from a slab of thin randomly oriented dielectric discs over a flat lossy ground is used to reconstruct the inclination angle and area distributions of the discs. The discs are employed to model a leafy agricultural crop, such as soybeans, in the L-band microwave region of the spectrum. The distorted Born approximation, along with a thin disc approximation, is used to obtain a relationship between the horizontal-like polarized backscattering coefficient and the joint probability density of disc inclination angle and disc radius. Assuming large skin depth reduces the relationship to a linear Fredholm integral equation of the first kind. Due to the ill-posed nature of this equation, a Phillips-Twomey regularization method with a second difference smoothing condition is used to find the inversion. Results are obtained in the presence of 1 and 10 percent noise for both leaf inclination angle and leaf radius densities.

43 citations

References
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Book
01 Jan 1950

9,085 citations

Journal ArticleDOI
28 Sep 1963-Nature
TL;DR: In this paper, the optical echoes from atmospheric constituents in the upper regions were detected by optical radar using a single-antenna (SINR) detector, and the optical radar was used to detect the optical echo.
Abstract: Detection of the optical echoes from atmospheric constituents in the upper regions by optical radar

225 citations

Journal ArticleDOI
TL;DR: In this article, the vertical profiles of aerosol extinction and backscatter in the troposphere were obtained from multi-zenith angle lidar measurements, and a regression analysis with respect to zenith angles for a layer integration of the angle dependent lidar equation in order to determine the optical thickness and aerosols extinction-to-backscatter ratio for defined atmospheric layers and the subsequent evaluation of cross-section profiles.
Abstract: The paper reports on vertical profiles of aerosol extinction and backscatter in the troposphere which were obtained from multi zenith angle lidar measurements. It is reported that a direct slant path solution was found to be not possible due to horizontal inhomogeneity of the atmosphere. Attention is given to the use of a regression analysis with respect to zenith angle for a layer integration of the angle dependent lidar equation in order to determine the optical thickness and aerosol extinction-to-backscatter ratio for defined atmospheric layers and the subsequent evaluation of cross-section profiles.

132 citations

Journal ArticleDOI
TL;DR: In this paper, 15 lidar observations of the stratosphere aerosol were made between February and November 1975, and all observations revealed the greatly increased particulate backscattering that followed the eruption of the volcano Fuego in October 1974.
Abstract: Fifteen lidar observations of the stratosphere aerosol were made between February and November 1975. All observations revealed the greatly increased particulate backscattering that followed the eruption of the volcano Fuego in October 1974. Vertical structure consisted initially of multiple layers, which later merged to form a single, broader peak. Nearly all of the increased scattering was confined to altitudes below 20 km. Hence, aerosol layer centroids in 1975 were typically several kilometers below their altitude prior to the eruption. Our observations began in mid-February, at about the time of maximum northern midlatitude influence of the volcanic injection. From late February on, both vertically integrated particulate back-scattering and the peak ratio of particulate to gaseous backscattering displayed approximately exponential declines, with mean 1/e lifetimes of eight and eleven months, respectively. These relatively short residence times are a combined consequence of the low altitude of...

57 citations