scholarly journals Depolarization ratios retrieved by AERONET sun–sky radiometer data and comparison to depolarization ratios measured with lidar

2017 ◽  
Vol 17 (10) ◽  
pp. 6271-6290 ◽  
Author(s):  
Youngmin Noh ◽  
Detlef Müller ◽  
Kyunghwa Lee ◽  
Kwanchul Kim ◽  
Kwonho Lee ◽  
...  
Keyword(s):  
Correlation Coefficients ◽  
Anthropogenic Pollution ◽  
Single Scattering ◽  
Size Distributions ◽  
Depolarization Ratio ◽  
Particle Size Distributions ◽  
Coarse Mode ◽  
Fine Mode ◽  
High Share ◽  
Depolarization Ratios

Abstract. The linear particle depolarization ratios at 440, 675, 870, and 1020 nm were derived using data taken with the AERONET sun–sky radiometer at Seoul (37.45° N, 126.95° E), Kongju (36.47° N, 127.14° E), Gosan (33.29° N, 126.16° E), and Osaka (34.65° N, 135.59° E). The results are compared to the linear particle depolarization ratio measured by lidar at 532 nm. The correlation coefficient R2 between the linear particle depolarization ratio derived by AERONET data at 1020 nm and the linear particle depolarization ratio measured with lidar at 532 nm is 0.90, 0.92, 0.79, and 0.89 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficients between the lidar-measured depolarization ratio at 532 nm and that retrieved by AERONET at 870 nm are 0.89, 0.92, 0.76, and 0.88 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficients for the data taken at 675 nm are lower than the correlation coefficients at 870 and 1020 nm, respectively. Values are 0.81, 0.90, 0.64, and 0.81 at Seoul, Kongju, Gosan, and Osaka, respectively. The lowest correlation values are found for the AERONET-derived linear particle depolarization ratio at 440 nm, i.e., 0.38, 0.62, 0.26, and 0.28 at Seoul, Kongju, Gosan, and Osaka, respectively. We should expect a higher correlation between lidar-measured linear particle depolarization ratios at 532 nm and the ones derived from AERONET at 675 and 440 nm as the lidar wavelength is between the two AERONET wavelengths. We cannot currently explain why we find better correlation between lidar and AERONET linear particle depolarization ratios for the case that the AERONET wavelengths (675, 870, and 1020 nm) are significantly larger than the lidar measurement wavelength (532 nm). The linear particle depolarization ratio can be used as a parameter to obtain insight into the variation of optical and microphysical properties of dust when it is mixed with anthropogenic pollution particles. The single-scattering albedo increases with increasing measurement wavelength for low linear particle depolarization ratios, which indicates a high share of fine-mode anthropogenic pollution. In contrast, single-scattering albedo increases with increasing wavelength for high linear particle depolarization ratios, which indicated a high share of coarse-mode mineral dust particles. The retrieved volume particle size distributions are dominated by the fine-mode fraction if linear particle depolarization ratios are less than 0.15 at 532 nm. The fine-mode fraction of the size distributions decreases and the coarse-mode fraction of the size distribution increases for increasing linear particle depolarization ratio at 1020 nm. The dust ratio based on using the linear particle depolarization ratio derived from AERONET data is 0.12 to 0.17. These values are lower than the coarse-mode fraction derived from the volume concentrations of particle size distributions, in which case we can compute the coarse-mode fraction of dust.

scholarly journals Depolarization Ratios Retrieved by AERONET Sun/Sky Radiometer Data and Comparison to Depolarization Ratios Measured With Lidar

2017 ◽  
Author(s):  
Youngmin Noh ◽  
Detlef Müller ◽  
Kyunghwa Lee ◽  
Kwanchul Kim ◽  
Kwonho Lee
Keyword(s):  
Particle Size ◽  
Correlation Coefficient ◽  
Single Scattering ◽  
Size Distributions ◽  
Depolarization Ratio ◽  
Particle Size Distributions ◽  
Coarse Mode ◽  
Fine Mode ◽  
532 Nm ◽  
Depolarization Ratios

Abstract. The linear particle depolarization ratios at 440, 675, 870, and 1020 nm were derived using data taken with AERONET sun/sky radiometer at Seoul (37.45° N, 126.95° E), Kongju (36.47° N, 127.14° E), Gosan (33.29° N, 126.16° E), and Osaka (34.65° N, 135.59° E). The results are compared to the linear particle depolarization ratio measured by lidar at 532 nm. The correlation coefficient R2 between the linear particle depolarization ratio derived by AERONET data at 1020 nm and the linear particle depolarization ratio measured with lidar at 532 nm is 0.90, 0.92, 0.79, and 0.89 at Seoul, Kongju, Gosan, and Osaka, respectively. A good correlation between the lidar-measured depolarization ratio at 532 nm and the one retrieved by AERONET at 870 nm. We find correlation coefficients R2 of 0.89, 0.92, 0.76, and 0.88 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficient for the data at 675 nm is lower than the correlation coefficient at 870 and 1020 nm. We find correlation values of 0.81, 0.90, 0.64, and 0.81 at Seoul, Kongju, Gosan, and Osaka, respectively. The lowest correlation values are found for the AERONET-derived linear particle depolarization ratio at 440 nm. We find values of 0.38, 0.62, 0.26, and 0.28 at Seoul, Kongju, Gosan, and Osaka, respectively. The linear particle depolarization ratio can be used as a parameter to obtain insight into the variation of optical and microphysical properties of dust when it mixed with anthropogenic pollution particles. The single-scattering albedo decreases with increasing measurement wavelength for low linear particle depolarization ratios. In contrast, single-scattering albedo increases with decreasing wavelength for high linear particle depolarization ratios. The retrieved volume particle size distributions are dominated by the fine-mode fraction if linear particle depolarization ratios are less than 0.15 at 532 nm. The fine-mode fraction of the size distributions decreases and the coarse-mode fraction of the size distribution increases for increasing the linear particle depolarization ratio at 1020 nm. The dust ratio based on using the linear particle depolarization ratio derived from AERONET data is 0.12 to 0.17 lower than the coarse-mode fraction derived from the volume concentrations of particle size distributions in which case we can compute the coarse-mode fractions of dust.

scholarly journals Dicarboxylic acids, oxoacids, benzoic acid, <i>α</i>-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

2016 ◽  
Vol 16 (8) ◽  
pp. 5263-5282 ◽  
Author(s):  
Dhananjay K. Deshmukh ◽  
Kimitaka Kawamura ◽  
Manuel Lazaar ◽  
Bhagawati Kunwar ◽  
Suresh K. R. Boreddy
Keyword(s):  
Organic Carbon ◽  
Benzoic Acid ◽  
Biomass Burning ◽  
Unsaturated Fatty Acids ◽  
Glyoxylic Acid ◽  
Water Soluble ◽  
Size Distributions ◽  
Strong Correlations ◽  
Coarse Mode ◽  
Fine Mode

Abstract. Size-segregated aerosols (nine stages from < 0.43 to > 11.3 µm in diameter) were collected at Cape Hedo, Okinawa, in spring 2008 and analyzed for water-soluble diacids (C2–C12), ω-oxoacids (ωC2–ωC9), pyruvic acid, benzoic acid, and α-dicarbonyls (C2–C3) as well as water-soluble organic carbon (WSOC), organic carbon (OC), and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and MSA−). In all the size-segregated aerosols, oxalic acid (C2) was found to be the most abundant species, followed by malonic and succinic acids, whereas glyoxylic acid (ωC2) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C2–C5), ωC2, and Gly as well as WSOC and OC peaked at fine mode (0.65–1.1 µm) whereas azelaic (C9) and 9-oxononanoic (ωC9) acids peaked at coarse mode (3.3–4.7 µm). Sulfate and ammonium were enriched in fine mode, whereas sodium and chloride were in coarse mode. Strong correlations of C2–C5 diacids, ωC2 and Gly with sulfate were observed in fine mode (r =  0.86–0.99), indicating a commonality in their secondary formation. Their significant correlations with liquid water content in fine mode (r =  0.82–0.95) further suggest an importance of the aqueous-phase production in Okinawa aerosols. They may also have been directly emitted from biomass burning in fine mode as supported by strong correlations with potassium (r =  0.85–0.96), which is a tracer of biomass burning. Bimodal size distributions of longer-chain diacid (C9) and oxoacid (ωC9) with a major peak in the coarse mode suggest that they were emitted from the sea surface microlayers and/or produced by heterogeneous oxidation of biogenic unsaturated fatty acids on sea salt particles.

scholarly journals Closure on the single scattering albedo in the WRF-Chem framework using data from the MILAGRO campaign

2009 ◽  
Vol 9 (1) ◽  
pp. 5009-5054
Author(s):  
J. C. Barnard ◽  
J. D. Fast ◽  
G. Paredes-Miranda ◽  
W. P. Arnott
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Chemical Properties ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Mean Values ◽  
Coarse Mode ◽  
Fine Mode ◽  
Using Data

Abstract. Data from the MILAGRO field campaign, which took place in the Mexico City Metropolitan Area (MCMA) during March 2006, is used to perform a closure experiment between aerosol chemical properties and aerosol optical properties. Measured aerosol chemical properties, obtained from the MILAGRO T1 site, are fed to two different "chemical to optical properties" modules. One module uses a sectional approach and is identical to that used in the WRF-Chem model, while the other is based on a modal approach. This modal code is employed as an independent check on the WRF-Chem module. Both modules compute aerosol optical properties and, in particular, the single-scattering albedo, ϖ0, as a function of time. The single-scattering albedos are compared to independent measurements obtained from a photoacoustic spectrometer (PAS). Because chemical measurements of the aerosol coarse mode were not available, and the inlet of the PAS could not ingest aerosols larger than about 2 to 3 μm, we focus here on the fine-mode ϖ0. At 870 nm, the wavelength of the PAS measurements, the agreement between the computed (modal and WRF-Chem) and observed fine-mode ϖ0, averaged over the course of the campaign, is reasonably good. The observed ϖ0 value is 0.77, while for both modules, the calculated value was 0.75 resulting in a difference of 0.02 between observations and both computational approaches. This difference is less than the uncertainty of the observed ϖ0 values (6%, or 0.05), and therefore "closure" is achieved, at least for mean values. After adjusting some properties of black carbon absorption and mass concentration within plausible uncertainty limits, the two modules simulate well the diurnal variation of ϖ0, and the absorption coefficient, Babs, but are less successful in calculating the variation of the scattering coefficient, Bscat. This difficulty is probably caused by the presence of larger particles during the day when windblown dust is ubiquitous; this dust likely increases the proportion of large particles introduced into the PAS. The dust also contributes to a very large aerosol mass loading in the coarse mode, and neglect of the coarse mode may cause significant errors, estimated to be as large as 0.07, in the calculation and measurement of ambient ϖ0. Finally, the observed ϖ0 is compared to the ϖ0 computed by the full WRF-Chem model, which includes prognostic aerosol chemistry. Unlike the results discussed above, a comparison between observed and simulated ϖ0 values reveals major differences. This large discrepancy is probably due, in part, to poor characterization of emissions near the T1 site, particularly black carbon emissions.

scholarly journals Comparison of the aerosol optical properties and size distribution retrieved by Sun photometer with in-situ measurements at mid-latitude

2016 ◽  
Author(s):  
Aurélien Chauvigné ◽  
Karine Sellegri ◽  
Maxime Hervo ◽  
Nadège Montoux ◽  
Patrick Freville ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
The Sun ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Near Surface ◽  
Atmospheric Column ◽  
Fine Mode ◽  
Sun Photometer

Abstract. Aerosols influence the Earth radiative budget through scattering and absorption of solar radiation. Several methods are used to investigate aerosol properties and thus quantify their direct and indirect impacts on climate. At the Puy de Dôme station, continuous high altitude near surface in-situ measurements and low altitude ground-based remote sensing atmospheric column measurements give the opportunity to compare the aerosol extinction measured with both methods over a one year period. To our knowledge, it is the first time that such a comparison is realized with continuous measurements of a high altitude site during a long term period. This comparison addresses to which extend near surface in-situ measurements are representative of the whole atmospheric column, the aerosol Mixing Layer (ML), or the Free Troposphere (FT). In particular, the impact of multi aerosol layers events detected using LIDAR backscatter profiles is analysed. A good correlation between in-situ aerosol extinction coefficient and Aerosol Optical Depth (AOD) measured by the Aerosol Robotic Network (AERONET) Sun photometer is observed with a correlation coefficient around 0.80, indicating that the in-situ measurements station is representative of the overall atmospheric column. After filtering for multilayer cases and correcting for each layer optical contribution (ML and FT), the atmospheric structure seems to be the main factor influencing the comparison between the two measurement techniques. When the site lies in the ML, the in-situ extinction represents 45 % of the Sun photometer ML extinction while when the site lies within the FT, the in-situ extinction is more than two times higher than the FT Sun photometer extinction. Remote sensing retrievals of the aerosol particle size distributions (PSD) from the Sun photometer observations are then compared to the near surface in-situ measurements, at dry and at ambient relative humidities. When in-situ measurements are considered at dry state, the in-situ fine mode diameters are 44 % higher than the Sun photometer-retrieved diameters and in-situ volume concentrations are 20 % lower than of the Sun photometer-retrieved fine mode concentration. Using a parametrised hygroscopic growth factor applied to aerosol diameters, the difference between in-situ and retrieved diameters grows larger. Coarse mode in-situ diameter and concentrations show a good correlation with retrieved particle size distributions from remote sensing.

scholarly journals The Influence of Wildfires on Aerosol Size Distributions in Rural Areas

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
E. Alonso-Blanco ◽  
A. I. Calvo ◽  
R. Fraile ◽  
A. Castro
Keyword(s):  
Particle Size ◽  
Rural Areas ◽  
Size Distributions ◽  
Average Increase ◽  
Particle Size Distributions ◽  
Before And After ◽  
Fine Mode ◽  
The Mean ◽  
The One ◽  
Number Of Particles

The number of particles and their size distributions were measured in a rural area, during the summer, using a PCASP-X. The aim was to study the influence of wildfires on particle size distributions. The comparative studies carried out reveal an average increase of around ten times in the number of particles in the fine mode, especially in sizes between 0.10 and 0.14 μm, where the increase is of nearly 20 times. An analysis carried out at three different points in time—before, during, and after the passing of the smoke plume from the wildfires—shows that the mean geometric diameter of the fine mode in the measurements affected by the fire is smaller than the one obtained in the measurements carried out immediately before and after (0.14 μm) and presents average values of 0.11 μm.

scholarly journals The MESSy aerosol submodel MADE3 (v2.0b): description and a box model test

2014 ◽  
Vol 7 (3) ◽  
pp. 1137-1157 ◽  
Author(s):  
J. C. Kaiser ◽  
J. Hendricks ◽  
M. Righi ◽  
N. Riemer ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Particle Size ◽  
Box Model ◽  
Aerosol Size Distribution ◽  
Sea Spray ◽  
Test Case ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Aerosol Dynamics ◽  
Coarse Mode ◽  
Made In

Abstract. We introduce MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, 3rd generation; version: MADE3v2.0b), an aerosol dynamics submodel for application within the MESSy framework (Modular Earth Submodel System). MADE3 builds on the predecessor aerosol submodels MADE and MADE-in. Its main new features are the explicit representation of coarse mode particle interactions both with other particles and with condensable gases, and the inclusion of hydrochloric acid (HCl) / chloride (Cl) partitioning between the gas and condensed phases. The aerosol size distribution is represented in the new submodel as a superposition of nine lognormal modes: one for fully soluble particles, one for insoluble particles, and one for mixed particles in each of three size ranges (Aitken, accumulation, and coarse mode size ranges). In order to assess the performance of MADE3 we compare it to its predecessor MADE and to the much more detailed particle-resolved aerosol model PartMC-MOSAIC in a box model simulation of an idealised marine boundary layer test case. MADE3 and MADE results are very similar, except in the coarse mode, where the aerosol is dominated by sea spray particles. Cl is reduced in MADE3 with respect to MADE due to the HCl / Cl partitioning that leads to Cl removal from the sea spray aerosol in our test case. Additionally, the aerosol nitrate concentration is higher in MADE3 due to the condensation of nitric acid on coarse mode particles. MADE3 and PartMC-MOSAIC show substantial differences in the fine particle size distributions (sizes &amp;lesssim; 2 μm) that could be relevant when simulating climate effects on a global scale. Nevertheless, the agreement between MADE3 and PartMC-MOSAIC is very good when it comes to coarse particle size distributions (sizes &amp;gtrsim; 2 μm), and also in terms of aerosol composition. Considering these results and the well-established ability of MADE in reproducing observed aerosol loadings and composition, MADE3 seems suitable for application within a global model.

scholarly journals A Short Note on the Potential of Utilization of Spectral AERONET-Derived Depolarization Ratios for Aerosol Classification

Atmosphere ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 143 ◽  
Author(s):  
Il-Sung Zo ◽  
Sung-Kyun Shin
Keyword(s):  
Short Note ◽  
Single Scattering ◽  
Observation Data ◽  
Spectral Variation ◽  
Aerosol Classification ◽  
Fine Mode ◽  
Remote Sensing Techniques ◽  
Aerosol Types ◽  
Aerosol Type ◽  
Depolarization Ratios

We herein present the spectral linear particle depolarization ratios (δp) from an Aerosol Robotics NETwork (AERONET) sun/sky radiometer with respect to the aerosol type. AERONET observation sites, which are representative of each aerosol type, were selected for our study. The observation data were filtered using the Ångström exponent (Å), fine-mode fraction (FMF) and single scattering albedo (ω) to ensure that the obtained values of δp were representative of each aerosol condition. We report the spectral δp values provided in the recently released AERONET version 3 inversion product for observation of the following aerosol types: dust, polluted dust, smoke, non-absorbing, moderately-absorbing and high-absorbing pollution. The AERONET-derived δp values were generally within the range of the δp values measured from lidar observations for each aerosol type. In addition, it was found that the spectral variation of δp differed according to the aerosol type. From the obtained results, we concluded that our findings provide potential insight into the identification and classification of aerosol types using remote sensing techniques.

scholarly journals Polar organic marker compounds in atmospheric aerosols during the LBA-SMOCC 2002 biomass burning experiment in Rondônia, Brazil: sources and source processes, time series, diel variations and size distributions

2010 ◽  
Vol 10 (4) ◽  
pp. 10889-10923 ◽  
Author(s):  
M. Claeys ◽  
I. Kourtchev ◽  
V. Pashynska ◽  
G. Vas ◽  
R. Vermeylen ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Malic Acid ◽  
Transition Period ◽  
Size Distributions ◽  
Dry Period ◽  
Coarse Mode ◽  
Diel Variations ◽  
Fine Mode ◽  
Marker Compounds ◽  
Organic Marker Compounds

Abstract. Measurements of polar organic marker compounds were performed on aerosols that were collected at a pasture site in the Amazon basin (Rondônia, Brazil) using a High-Volume dichotomous sampler (HVDS) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). The samplings were conducted within the framework of the LBA-SMOCC (Large-Scale Biosphere Atmosphere Experiment in Amazônia – Smoke Aerosols, Clouds, Rainfall, and Climate: Aerosols From Biomass Burning Perturb Global and Regional Climate) campaign, which took place from 9 September till 14 November 2002, spanning the late dry season (biomass burning), the transition period, and the onset of the wet season (clean conditions). In the present study a more detailed discussion is presented compared to previous reports on the behavior of selected polar marker compounds, including: (a) levoglucosan, a tracer for biomass burning, (b) malic acid, a tracer for the oxidation of semivolatile carboxylic acids, (c) tracers for secondary organic aerosol (SOA) from isoprene, i.e., the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and the C5-alkene triols [2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene], and (d) sugar alcohols (arabitol, mannitol, and erythritol), tracers for fungal spores. The results obtained for levoglucosan are covered first with the aim to address its contrasting behavior with that of malic acid, the isoprene SOA tracers, and the fungal spore tracers. The tracer data are discussed taking into account new insights that recently became available into their stability and/or aerosol formation processes. During all three periods, levoglucosan was the most dominant identified organic species in the PM2.5 size fraction of the HVDS samples. In the dry period levoglucosan reached concentrations of up to 7.5 μg m−3 and exhibited diel variations with a nighttime prevalence. It was closely associated with the PM mass in the size-segregated samples and was mainly present in the fine mode, except during the wet period where it peaked in the coarse mode. Isoprene SOA tracers showed an average concentration of 250 ng m−3 during the dry period versus 157 ng m−3 during the transition period and 52 ng m−3 during the wet period. Malic acid and the 2-methyltetrols exhibited a different size distribution pattern: while the 2-methyltetrols were mainly associated with the fine mode during all periods, malic acid was prevalent in the fine mode only during the dry and transition periods, while it was dominant in the coarse mode during the wet period, consistent with different formation processes. The sum of arabitol, mannitol, and erythritol in the PM2.5 fraction of the HVDS samples during the dry, transition, and wet periods was, on average, 54 ng m−3, 34 ng m−3, and 27 ng m−3, respectively, and revealed minor day/night variation. The mass size distributions of arabitol and mannitol during all periods showed similar patterns and an association with the coarse mode, consistent with their primary origin. The results show that even under the heavy smoke conditions of the dry period a natural background with contributions from bioaerosols and isoprene SOA can be revealed. The enhancement in isoprene SOA in the dry season is mainly attributed to an increased acidity of the aerosols and a decreased wet deposition.

scholarly journals Multiwavelength and polarization lidar measurements of Asian dust layers over Tsukuba, Japan: a case study

2007 ◽  
Vol 7 (4) ◽  
pp. 10179-10203 ◽  
Author(s):  
T. Sakai ◽  
T. Nagai ◽  
T. Kobayashi ◽  
A. Yamazaki ◽  
A. Uchiyama ◽  
...  
Keyword(s):  
Asian Dust ◽  
Aerosol Layer ◽  
Lidar Measurement ◽  
Nonspherical Particles ◽  
Depolarization Ratio ◽  
Dust Layer ◽  
Coarse Mode ◽  
Fine Mode ◽  
Aerosol Properties

Abstract. Elastic and polarization lidar was used to measure the vertical profiles of aerosol backscattering coefficients at wavelengths of 355, 532, 735, and 1064 nm, and the depolarization ratio at 532 nm in order to study the aerosol properties in the free troposphere over Tsukuba, Japan, in 2006. An elevated dust layer was observed at altitudes between 3 and 8.5 km on 1 April during the Asian dust period. The wavelength exponents of the aerosol backscattering coefficient (k) were –0.1 to 0.5, and the depolarization ratio (δp) was 25% for the dust layer, suggesting the predominance of supermicrometer-sized (coarse mode) nonspherical particles. An aerosol layer observed at altitudes between 1.5 and 5 km on 19 October during the less-dust period exhibited the values of k=1.0 to 1.6 and δp=1 to 13%, suggesting the predominance of submicrometer-sized (fine mode) particles. In those layers, the values of k and δp varied with height; they were also negatively correlated, suggesting that the proportion of the coarse nonspherical particles to total particles varied. The particle size distributions estimated from the observed values and the theoretical computation revealed number mode radii of 0.3 &amp;mum; for the coarse mode and 0.1 &amp;mum; for the fine mode, assuming bimodal distribution. These results were consistent with those obtained from the sky-radiometer measurements, although they revealed another mode in the larger radius. The column volume concentration derived from the lidar was 48% lower than that derived from the sky-radiometer on 1 April and 16% lower on 19 October. The optical thickness derived from the lidar was 12% lower than that obtained from the sky-radiometer on 1 April and 29% higher on 19 October. Further case study is necessary to validate the method for estimating aerosol properties based on the lidar measurement.

scholarly journals Dicarboxylic acids, oxoacids, benzoic acid, α-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

2015 ◽  
Vol 15 (18) ◽  
pp. 26509-26554 ◽  
Author(s):  
D. K. Deshmukh ◽  
K. Kawamura ◽  
M. Lazaar ◽  
B. Kunwar ◽  
S. K. R. Boreddy
Keyword(s):  
Organic Carbon ◽  
Benzoic Acid ◽  
North Pacific ◽  
Western North Pacific ◽  
Sea Salt ◽  
Water Soluble ◽  
Pacific Rim ◽  
Size Distributions ◽  
Coarse Mode ◽  
Fine Mode

Abstract. Size-segregated aerosols (9-stages from < 0.43 to > 11.3 μm in diameter) were collected at Cape Hedo, Okinawa in spring 2008 and analyzed for water-soluble diacids (C2–\\C12), ω-oxoacids (ωC2–ωC9), pyruvic acid, benzoic acid and α-dicarbonyls (C2–C3) as well as water-soluble organic carbon (WSOC), organic carbon (OC) and major ions. In all the size-segregated aerosols, oxalic acid (C2) was found as the most abundant species followed by malonic and succinic acids whereas glyoxylic acid (ωC2) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C2–C5), ωC2 and Gly as well as WSOC and OC peaked at 0.65–1.1 μm in fine mode whereas azelaic (C9) and 9-oxononanoic (ωC9) acids peaked at 3.3–4.7 μm in coarse mode. Sulfate and ammonium are enriched in fine mode whereas sodium and chloride are in coarse mode. These results imply that water-soluble species in the marine aerosols could act as cloud condensation nuclei (CCN) to develop the cloud cover over the western North Pacific Rim. The organic species are likely produced by a combination of gas-phase photooxidation, and aerosol-phase or in-cloud processing during long-range transport. The coarse mode peaks of malonic and succinic acids were obtained in the samples with marine air masses, suggesting that they may be associated with the reaction on sea salt particles. Bimodal size distributions of longer-chain diacid (C9) and oxoacid (ωC9) with a major peak in the coarse mode suggest their production by photooxidation of biogenic unsaturated fatty acids via heterogeneous reactions on sea salt particles.

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