Determination of Aerosol Height Distributions by Lidar

Fernald, F. G.; Herman, Benjamin M.; Reagan, John A.

doi:10.1175/1520-0450(1972)011<0482:doahdb>2.0.co;2

Cited by 397 publications

(267 citation statements)

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“…Generally, the two unknowns of this equation, the backscatter and extinction coefficients, have to be related using either empirical or theoretical methods in order to be able to invert the lidar equation. There have been many discussions regarding the solutions of the lidar (e.g., Barrett and Ben-Dov, 1967;Viezee et al, 1969;Davis, 1969;Fernald, 1972;Platt, 1973Platt, , 1979Klett, 1981;Fernald, 1984;Flamant, 1996, andAnsmann et al, 1992). Forward solution of the backscatter coefficient was found to become rapidly unstable for optical depths greater than unity, unless the lidar ratio was specified with extreme accuracy (Platt, 1979).…”

Section: Methodsmentioning

confidence: 99%

“…Elastic backscatter and Raman lidars have been used to retrieve information on geometrical and optical properties of cirrus clouds, made through the application of methods that have been earlier demonstrated in the literature (e.g. Barrett and Ben-Dov, 1967;Viezee et al, 1969;Davis, 1969;Fernald et al , 1972;Platt, 1973;Platt, 1979;Klett, 1981;Fernald, 1984;Grund and Eloranta, 1990;Ansmann et al, 1992). Some key microphysical parameters are the extinction coefficient, lidar ratio and depolarization ratio as well as the mid-altitude and the corresponding mid-cloud temperature of cirrus clouds (Sunilkumar and Parameswaran, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The evaluation of optical depth of cirrus clouds was done through the application of different methods which are already demonstrated in the literature. Most of these methods depend on the solution of the standard lidar equation (Barrett and Ben-Dov, 1967;Viezee et al, 1969;Davis, 1969;Fernald et al, 1972;Platt, 1973Platt, , 1979Klett, 1981;Fernald, 1984;Ansmann et al, 1992;Elouragini and Flamant, 1996;Wandinger, 1998). A different technique to determine the optical depth of cirrus clouds from elastic lidar signal has also been developed.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Giannakaki¹,

Balis²,

Amiridis

et al. 2007

Atmos. Chem. Phys.

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Abstract. Optical and geometrical characteristics of cirrus clouds over Thessaloniki, Greece (40.6 • N, 22.9 • E) have been determined from the analysis of lidar and radiosonde measurements performed during the period from 2000 to 2006. Cirrus clouds are generally observed in a mid-altitude region ranging from 8.6 to 13 km, with mid-cloud temperatures in the range from −65 • to −38 • C. The cloud thickness generally ranges from 1 to 5 km and 38% of the cases studied have thickness between 2 and 3 km. The retrieval of optical depth and lidar ratio of cirrus clouds is performed using three different methods, taking into account multiple scattering effect. The mean optical depth is found to be 0.31±0.24 and the corresponding mean lidar ratio is 30±17 sr following the scheme of Klett-Fernald method. Sub-visual, thin and opaque cirrus clouds are observed at 3%, 57% and 40% of the measured cases, respectively. A comparison of the results obtained between the three methods shows good agreement. The multiple scattering errors of the measured effective extinction coefficients range from 20 to 60%, depending on cloud optical depth. The temperature and thickness dependencies on optical properties have also been studied in detail. A maximum mid-cloud depth of ∼3.5 km is found at temperatures around ∼−47.5 • C, while there is an indication that optical depth and mean extinction coefficient increases with increasing mid-cloud temperature. A correlation between optical depth and thickness was also found. However, no clear dependence of the lidar ratio values on the cloud temperature and thickness was found.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Giannakaki¹,

Balis²,

Amiridis

et al. 2007

Atmos. Chem. Phys.

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“…This poses an obvious dilemma as there are two unknowns, P,(r) and aa(r), and only one measurement, V(r), at any range r. This difficulty may be overcome by imposing certain constraints on the problem. As shown by Fernald et al (1972), if it is assumed that the aerosol extinctionto-backscatter ratio, or Sa ratio, S, = a,/P,, is constant over some height interval, the lidar equation may be solved to retrieve a,(r) over that interval. Assuming S, is constant with height requires that the shape of the aerosol size distribution and the aerosol particle refractive index be height invariant.…”

Section: Monostatic Lidarmentioning

confidence: 99%

Lidar and Balloon-Borne Cascade Impactor Measurements of Aerosols: A Case Study

Reagan

Apte

Bruhns

et al. 1984

Aerosol Science and Technology

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Aerosol size distributions, elemental components, complex refractive indices, extinction profiles and extinctionto-backscatter ratios have been measured and inferred from balloon-borne cascade impactor and lidar observations made during a cooperative joint experiment conducted during the period 4-10 April, 1980 in Tucson, AZ. Size distributions obtained from quartz crystal microbalance (QCM) cascade impactor measurements at different heights (1 to 1000 m) and times over a period of several days were fairly similar in form, being clearly bimodal in their mass distributions with the coarse particle mode being dominant. Electron microscope and energy dispersive X-ray analyses of particles deposited on the QCM stages over the particle radii range -0.5-4.0 ym revealed that the particle samples were elementally dominated by both sulfur and crustal type (Al, Ca, Mg and Si) elements. Complex refractive index estimates for a wavelength of 649 nm were obtained by comparing the lidar inferred aerosol extinction-to-backscatter ratios with theoretically computed values calculated for the impactor-derived size distributions. The real part of the index was estimated to be 1.45 for most cases, while the estimates for the imaginary part ranged between 0.000 and 0.01. Aerosol extinction coefficients calculated for the impactor-derived size distributions were found to be somewhat smaller but in fair agreement with the extinction coefficients retrieved from the lidar measurements.

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“…Although a ratio quantity, Sa has units of steradian; the units will not be shown explicity in the discussions, tables and figures presented here. Solution techniques for solving the lidar equation to extract profiles of aerosol backscatter and/or extindtion from such lidar measurements generally assume some constraint for S, (e.g., Barrett and Ben-Dov, 1967;Fernald et al, 1972;Klett, 1981). The most common assumption is that S, is constant over a specified range interval.…”

Section: Introductionmentioning

confidence: 99%