A survey of light‐scattering techniques used in the remote monitoring of atmospheric aerosols

Deirmendjian, D.

doi:10.1029/rg018i002p00341

Cited by 40 publications

(6 citation statements)

References 122 publications

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“…The retrieval of aerosol size distribution information from multispectral extinction measurements is very complex and of limited accuracy due to inherent instabilities in the mathematical inversion process [Deirmendjian, 1980]. Such is the case of SAGE II, which offers only four aerosol extinction measurements over a rather restricted wavelength domain [Chu et al, 1989].…”

Section: Sage II Analysis Techniquementioning

confidence: 99%

Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Thomason¹,

Poole²

1993

J. Geophys. Res.

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Physical properties of the stratospheric aerosol population are inferred from cloud‐free SAGE II multiwavelength extinction measurements in the Antarctic during late summer (February/March) and spring (September/October, November). Seasonal changes in these properties are used to infer physical processes occurring in the Antarctic stratosphere over the course of the winter. The analysis suggests that the apparent springtime cleansing of the Antarctic stratosphere is the result of aerosol redistribution through subsidence of the polar vortex air mass and sedimentation of large polar stratospheric cloud particles. The analysis also suggests that vortex processes are responsible for a significant downward transport of aerosol through the tropopause.

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Section: Sage II Analysis Techniquementioning

confidence: 99%

Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Thomason¹,

Poole²

1993

J. Geophys. Res.

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“…The modern Stratospheric Aerosol Measurement (SAM) 2 and Stratospheric Aerosol and Gas Experiment (SAGE) satellites utilize a similar technique (at slightly different wavelengths) with an automated data acquisition system to provide nearly continuous, global scale monitoring of the aerosols [McCormick et al, , b, 1982aRussell et al, 1981a, b;Swissler et al, 1982]. Fymat and Smith [1980] and Deirmendjian [1980] have reviewed the status of light-sensing methods for aerosol detection.…”

Section: Measurement Techniquesmentioning

confidence: 99%

Stratospheric aerosols: Observation and theory

Turco¹,

Whitten²,

Toon³

1982

Reviews of Geophysics

279

105

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We review current observational and theoretical knowledge of the stratospheric aerosols. These particles, which are composed primarily of sulfuric acid and other sulfates, are concentrated in a layer extending 20 km or more above the tropopause. The aerosols affect the chemistry of the stratosphere and the climatology of the earth. A number of important chemical and physical roles for the aerosols are discussed. We describe the properties of stratospheric aerosols as revealed by experimental data. Remote-sensing optical instruments, both active (lidars) and passive (satellites), allow routine mapping of the global aerosol distribution. Extensive in situ measurements obtained by mechanical collection (filters and impactors) and scattered-light detection yield the overall size dispersion of the aerosols. Laboratory analyses of preserved aerosol samples define the bulk composition (and possible origins) of the particles. Quantitative studies of aerosol precursor gases (SO2, OCS, and CS2) by wet chemical, cryogenic, and spectroscopic techniques reveal the photochemical sources of particulate mass. Theoretical aspects of the stratospheric aerosols are also reviewed. We discuss aerosol chemical reactions including those of gaseous precursors, those i n aqueous solution, and thos e on particle surfaces. We also describe aerosol microphysical processes including nucleation, condensation/ evaporation, coagulation, and sedimentation. Existing models of aerosols which incorporate these chemical and physical processes are outlined. Aerosol model predictions are appraised vis h vis observations. The simulations are shown to agree with measurements in many important respects. Areas requiring further investigation include the identification of the nucleation mechanisms for the aerosols and the characterization of the tenuous upper extent of the aerosol layer above ---25 km. Estimates are presented for the potential aerosol changes attributable to the emissions of particles and gases by aerospace operations (aircraft and rockets) and industrial consumption of fossil fuels. It is demonstrated that although the climatic effects of existing levels of stratospheric aerosol pollution are negligible, potential increases in those levels might pose a future threat. Evidence for a major influence of massive volcanic eruptions on terrestrial climate is discussed. Model calculations of climate perturbations associated with past volcanic activity are summarized. In addition, detailed physico-

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“…Instrumentation for measuring sizing distributions has continued to occupy a prominent position among problems in atmospheric sciences. Although significant advances have been made in the past decades [Deirmendjian, 1980;Knollenberg, 1981;Kerker, 1997], a serious problem inherent in the particle-sizing instrumentation remains: the associated mathematical problem that needs to be solved to obtain size distributions is ill-posed in the sense that measured size distributions are highly sensitive to errors in measured signals and calculated scattering properties. This is particularly true for indirect retrieval [Twomey, 1977].…”

Section: Introductionmentioning

confidence: 99%

Particle size distribution retrieval from multispectral optical depth: Influences of particle nonsphericity and refractive index

Liu¹,

Arnott²,

Hallett³

1999

J. Geophys. Res.

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Abstract. Retrieval of size distributions from multispectral optical depth measurements requires solution of an ill-posed inverse problem. The ill-posedness causes problems such as solution ambiguity. Size distribution retrieval becomes more complicated in the presence of nonspherical particles and/or refractive index errors. A new retrieval algorithm is first developed which allows for both smoothing and nonnegativity constraint along with the L-curve method for choosing the Lagrange multiplier that controls the degree of the imposed smoothing. This new algorithm is compared to an iterative algorithm and the method of truncated singular value decomposition, demonstrating that the new algorithm outperforms the other two. With the new algorithm to perform the size distribution retrieval and with the T-matrix method to calculate optical depth for a given cloud consisting of randomly oriented finite circular cylinders, the influence of particle nonsphericity on the size distribution retrieval is investigated by use of the Mie theory for spheres as well as the anomalous diffraction theory for cylinders. The results show that spurious particles and even spurious particle modes occur for both approximations. The effect of refractive index errors are also investigated, showing that even a small perturbation of refractive indices can cause serious distortions of retrieved size distributions. A further examination reveals that either applying an approximate lightscattering theory (Mie theory or anomalous diffraction theory) to nonspherical particles or using incorrect refractive indices results in systematic errors in the model which in turn conspire with the ill-posedness inherent in the retrieval to cause the distortions of retrieved size distributions. The retrieval process essentially transforms the model error into the error in retrieved size distribution, yet improves the agreement between true and retrieved optical depth. IntroductionVarious properties (e.g., dynamical, optical, electrical, and chemical) of atmospheric particles depend on particle size. Number distribution of particles with respect to size (size distribution) is a fundamental subject in aerosol and cloud physics [Pruppacher and Klett, 1978]. Its importance has been increasingly recognized with the concern over the effects of aerosols

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A survey of light‐scattering techniques used in the remote monitoring of atmospheric aerosols

Cited by 40 publications

References 122 publications

Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Stratospheric aerosols: Observation and theory

Particle size distribution retrieval from multispectral optical depth: Influences of particle nonsphericity and refractive index

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