Combined raman elastic-backscatter LIDAR for vertical profiling of moisture, aerosol extinction, backscatter, and LIDAR ratio

Ansmann, Albert; Riebesell, M.; Wandinger, Ulla; Weitkamp, C.; Voss, E.; Lahmann, W.; Michaelis, W.

doi:10.1007/bf00348608

Cited by 412 publications

(301 citation statements)

References 32 publications

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“…3.2 Calculation of particle extinction coefficient ELDA calculates profiles of particle extinction coefficients with the Raman method (Ansmann et al, 1990(Ansmann et al, , 1992a) from pre-processed Raman signals. Those signals are already corrected for incomplete overlap, background, range dependency and other system specific effects.…”

Section: Comparison Of Different Backscatter Methodsmentioning

confidence: 99%

“…-extinction coefficient: (in SCC web-interface referred to as "extinction only"): profile of particle extinction coefficient α which is calculated with the Raman method (Ansmann et al, 1990(Ansmann et al, , 1992a, and -lidar ratio: (in SCC web-interface referred to as "lidar ratio and extinction") which consists of a particle extinction profile and the corresponding particle backscatter profile, both obtained with the Raman method and with the same effective vertical resolution. This product allows for the calculation of a profile of the particle lidar ratio S.…”

Section: Earlinet Lidar Data Analyzer (Elda)mentioning

confidence: 99%

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EARLINET Single Calculus Chain – technical – Part 2: Calculation of optical products

et al. 2016

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Abstract. In this paper we present the automated software tool ELDA (EARLINET Lidar Data Analyzer) for the retrieval of profiles of optical particle properties from lidar signals. This tool is one of the calculus modules of the EARLINET Single Calculus Chain (SCC) which allows for the analysis of the data of many different lidar systems of EARLINET in an automated, unsupervised way. ELDA delivers profiles of particle extinction coefficients from Raman signals as well as profiles of particle backscatter coefficients from combinations of Raman and elastic signals or from elastic signals only. Those analyses start from pre-processed signals which have already been corrected for background, range dependency and hardware specific effects. An expert group reviewed all algorithms and solutions for critical calculus subsystems which are used within EARLINET with respect to their applicability for automated retrievals. Those methods have been implemented in ELDA. Since the software was designed in a modular way, it is possible to add new or alternative methods in future. Most of the implemented algorithms are well known and well documented, but some methods have especially been developed for ELDA, e.g., automated vertical smoothing and temporal averaging or the handling of effective vertical resolution in the case of lidar ratio retrievals, or the merging of near-range and far-range products. The accuracy of the retrieved profiles was tested following the procedure of the EARLINET-ASOS algorithm inter-comparison exercise which is based on the analysis of synthetic signals. Mean deviations, mean relative deviations, and normalized root-mean-square deviations were calculated for all possible products and three height layers. In all cases, the deviations were clearly below the maximum allowed values according to the EARLINET quality requirements.

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Section: Comparison Of Different Backscatter Methodsmentioning

confidence: 99%

Section: Earlinet Lidar Data Analyzer (Elda)mentioning

confidence: 99%

EARLINET Single Calculus Chain – technical – Part 2: Calculation of optical products

et al. 2016

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“…[6] The backscattering ratio (R) is computed from the Raman oxygen signal and Mie/Rayleigh signals [Ansmann et al, 1992;Whiteman et al, 1992;Shibata et al, 1996b], and is defined as…”

Section: Raman Lidar Measurementsmentioning

confidence: 99%

“…[3] Raman lidar is an effective tool for remotely measuring the vertical distribution of free tropospheric aerosol optical properties, as well as humidity [e.g., Whiteman et al, 1992;Ansmann et al, 1992]. Using this technique, Kwon et al [1997] and Sakai et al [2000] have shown that the depolarization ratio in the free troposphere is generally high (>10%) over a wide range of relative humidities in the spring over Nagoya in Japan, probably due to the transport of mineral dust particles from the Asian arid regions.…”

Section: Introductionmentioning

confidence: 99%

Raman lidar and aircraft measurements of tropospheric aerosol particles during the Asian dust event over central Japan: Case study on 23 April 1996

et al. 2003

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[1] The vertical distributions of tropospheric aerosol properties were measured during the Asian dust event over central Japan (35°-36°N, 136°-137°E), using a ground-based Raman lidar and aircraft-based instruments on 23 April 1996. The lidar measured enhancements of aerosol backscattering below an altitude of 4 km and between 5 and 8 km where the total aerosol linear depolarization ratio showed peaks of 12-15% and the relative humidities were $30%. The aircraft measurements showed that the aerosol particles consisted primarily of irregularly shaped mineral dusts and sea salts with a mode radius (r m ) of $1 mm and sulfates with r m $ 0.1 mm over the measured height range of 0.6-5.5 km. Electron microscopic analyses suggest that $77% of the mineral particles were coated with a solution at 1.8 km and that the fraction of coated particles decreased with height. The aerosol backscattering coefficients (b a ), calculated from the airborne optical particle counter (OPC) data, were smaller than the lidar-derived values by $30% above 3.1 km and by $44% below that altitude. The difference was attributable to the horizontal and temporal inhomogeneities of the aerosol properties between the measurement sites and to the uncertainty in b a , particularly for the coarse particles calculated from the OPC data. The aerosol depolarization ratios (d a ) estimated from the OPC data showed the same increase as those obtained with the lidar above 4.1 km. This suggests that the proportion of backscattering by coarse particles to total particles primarily controlled the d a measured with the lidar in that region.

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“…However, retrieval of the aerosol extinction profile from backscattered LIDAR measurements requires knowledge of the aerosol extinctionto-backscatter ratio (Fernald, 1984). In previous studies, this problem has been solved by using the high spectral resolution LIDAR techniques (Grund and Eloranta, 1991) or elasticRaman LIDAR measurements (Ansmann et al, 1992), which have been automatically running in Oklahoma and in the Arctic as well as in the framework of EARLINET (Razenkov et al, 2004;Mattis et al, 2004) since 2000. Although both techniques allow simultaneous determination of the aerosol extinction and backscattered coefficients, one should bear in mind that both signals are sensitive to the background noise induced by scattering from ambient aerosol.…”

Section: Introductionmentioning

confidence: 99%

A study on the aerosol extinction-to-backscatter ratio with combination of micro-pulse LIDAR and MODIS over Hong Kong

Mao

et al. 2006

Atmos. Chem. Phys.

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Abstract. The aerosol extinction-to-backscatter ratio is an important parameter for inverting LIDAR signals in the LI-DAR equation. It is a complicated function of the aerosol microphysical characteristics. In this paper, a method to retrieve the column-averaged aerosol extinction-to-backscatter ratio by constraining the aerosol optical depths (AOD) from a Micro-pulse LIDAR (MPL) by the AOD measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. Both measurements were taken on cloud free days between 1 May 2003 and 30 June 2004 over Hong Kong, a coastal city in south China. Simultaneous measurements of aerosol scattering coefficients with a forward scattering visibility sensor are compared with the LI-DAR retrieval of aerosol extinction coefficients. The data are then analyzed to determine seasonal trends of the aetrosol extinction-to-backscatter ratio. In addition, the relationships between the extinction-to-backscatter ratio and wind conditions as well as other aerosol microphysical parameters are presented. The mean aerosol extinction-to-backscatter ratio for the whole period was found to be 29.1±5.8 sr, with a minimum of 18 sr in July 2003 and a maximum of 44 sr in March 2004. The ratio is lower in summer because of the dominance of oceanic aerosols in association with the prevailing southwesterly monsoon. In contrast, relatively larger ratios are noted in spring and winter because of the increased impact of local and regional industrial pollutants associated with the northerly monsoon. The extended LIDAR measurements over Hong Kong provide not only a more accurate retrieval of aerosol extinction coefficient profiles, but also significant substantial information for air pollution and climate studies in the region.

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Combined raman elastic-backscatter LIDAR for vertical profiling of moisture, aerosol extinction, backscatter, and LIDAR ratio

Cited by 412 publications

References 32 publications

EARLINET Single Calculus Chain – technical – Part 2: Calculation of optical products

EARLINET Single Calculus Chain – technical – Part 2: Calculation of optical products

Raman lidar and aircraft measurements of tropospheric aerosol particles during the Asian dust event over central Japan: Case study on 23 April 1996

A study on the aerosol extinction-to-backscatter ratio with combination of micro-pulse LIDAR and MODIS over Hong Kong

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