Free tropospheric aerosol backscatter, depolarization ratio, and relative humidity measured with the Raman lidar at Nagoya in 1994–1997: contributions of aerosols from the Asian Continent and the Pacific Ocean

Sakai, Tetsu; Shibata, Takashi; Kwon, Soung-An; Kim, Yoon-Suk; Tamura, Koichi; Iwasaka, Yasunobu

doi:10.1016/s1352-2310(99)00328-3

Cited by 90 publications

(81 citation statements)

References 26 publications

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“…The values of d a,coarse were calculated from the OPC data using the T-matrix method, and were almost constant (21.9 $ 22.4%) over the height range of the measurement because the shape of the size distribution in that mode was almost constant (Figure 10). These values are somewhat smaller than the previously reported maximum values ($25%) measured in the Asian dust layer over Japan [Sakai et al, 2000[Sakai et al, , 2002Murayama, 2002].…”

Section: Total Aerosol Linear Depolarization Ratiocontrasting

confidence: 65%

“…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. Because the depolarization ratio is a measure of particle nonsphericity [e.g., Bohren and Huffman, 1983], it can be utilized to detect mineral dust particles since they are mostly nonspherical [e.g., Okada et al, 1987Okada et al, , 2001.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Total Aerosol Linear Depolarization Ratiocontrasting

confidence: 65%

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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“…During the Saharan Aerosol Long-range Transport and Aerosol-CloudInteraction Experiment (SALTRACE) winter campaign 2014 at Barbados, Haarig et al (2017) detected an increase of the particle depolarisation ratio up to 12 % at 355 nm, 15 % at 532 nm, and 10 % at 1064 nm when the RH drops below 50 %. Sakai et al (2000) observed low depolarisation ratios (< 5 %) at 532 nm over a wide range of relative humidities, whereas δ par > 10 % was measured at low RH (< 50 %) in air masses which had passed over the Pacific Ocean. In a laboratory chamber experiment, Sakai et al (2010) found linear depolarisation ratios at 532 nm of 1 ± 0.1 % for droplets, 8 ± 1 % for sea salt crystals, and 21 ± 2 % for NaCl crystals.…”

Section: Ps95 -Marine Aerosol Conditionsmentioning

confidence: 81%

Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures

et al. 2018

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Abstract. The multi-wavelength Raman lidar Polly XT has been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from north to south and vice versa. The lidar measurements of the RV Polarstern cruises PS95 from Bremerhaven, Germany, to Cape Town, Republic of South Africa (November 2015), and PS98 from Punta Arenas, Chile, to Bremerhaven, Germany (April/May 2016), are presented and analysed in detail. The latest set-up of Polly XT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver.Three case studies provide an overview of the aerosol detected over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at 355 nm (9 % at 532 nm) and thus confirming the non-sphericity of these particles, could be detected on top of the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cabo Verde islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case.A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the downmixing of dust in the tropics and anthropogenic influences in the northern latitudes, whereas the optical properties of the MBL in the Southern Hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4 and 9 % at 532 nm.Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio at 355 and 532 nm, and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for particle type, whereas the Ångström exponent is rather variable.

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“…Prospero et al, 2002) are lifted well into the free troposphere (e.g. Sakai et al, 2000;Gobbi et al, 2000;Sassen, 2002) and transported over thousands of kilometers (e.g. Duce et al, 1980;Prospero et al, 1983;Moulin et al, 1998;Karyampudi et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Matthias and Bosenberg, 2002;Del Guasta, 2002), or over the lower troposphere (e.g. Sakai et al, 2000;Balis et al, 2000;Franke et al, 2001;Schneider and Eixmann, 2002). Conversely, lidar profiles are mostly presented in case studies of specific aerosol events (e.g.…”

Section: Introductionmentioning

confidence: 99%

The vertical distribution of aerosols, Saharan dust and cirrus clouds in Rome (Italy) in the year 2001

2004

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Abstract.A set of 813 lidar profiles of tropospheric aerosol and cirrus clouds extinction and depolarization observed in Rome, Italy, between February 2001 and February 2002 is analyzed and discussed. The yearly record reveals a meaningful contribution of both cirrus clouds (38%) and Saharan dust (12%) to the total optical thickness (OT) of 0.26, at 532 nm. Seasonal analysis shows the planetary boundary layer (PBL) aerosols to be confined below 2 km in winter and 3.8 km in summer, with relevant OT shifting from 0.08 to 0.16, respectively. Cirrus clouds maximise in spring and autumn, in both cases with average OT similar to the PBL aerosols one. With the exception of winter months, Saharan dust is found to represent an important third layer mostly residing between PBL aerosols and cirrus clouds, with yearly average OT≈0.03. Saharan dust and cirrus clouds were detected in 20% and in 45% of the observational days, respectively. Validation of the lidar OT retrievals against collocated sunphotometer observations show very good agreement. These results represent one of the few yearly records of tropospheric aerosol vertical profiles available in the literature.

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Free tropospheric aerosol backscatter, depolarization ratio, and relative humidity measured with the Raman lidar at Nagoya in 1994–1997: contributions of aerosols from the Asian Continent and the Pacific Ocean

Cited by 90 publications

References 26 publications

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

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

Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures

The vertical distribution of aerosols, Saharan dust and cirrus clouds in Rome (Italy) in the year 2001

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