Water-soluble organic aerosol in the Los Angeles Basin and outflow regions: Airborne and ground measurements during the 2010 CalNex field campaign

Duong, H. T.; Sorooshian, Armin; Craven, J. S.; Hersey, S. P.; Metcalf, A. R.; Zhang, Xiaolu; Weber, R. J.; Jonsson, Haflidi H.; Flagan, Richard C.; Seinfeld, John H.

doi:10.1029/2011jd016674

Cited by 53 publications

(63 citation statements)

References 68 publications

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“…It was found that the ML height can vary by large amounts, up to as much as 2 km, in locations surrounding the ceilometer. This is likely due to variations of ML heights with the complex terrain, differing meteorological conditions over the ocean and mountains, and the transport of pollutants within the study region (Duong et al, 2011). Repeating the comparison between HSRL and ceilometer ML heights, we see that the comparison breaks down quickly at separations beyond 30 km.…”

Section: Comparison With Ceilometer and Investigation Of Spatial Varimentioning

confidence: 90%

“…The Los Angeles basin is bordered by the San Gabriel Mountains, the San Bernardino Mountains, and the Pacific Ocean. Duong et al (2011) discuss that the LA basin is impacted by sea breezes and mountain flows that can transport or trap aerosols. During CalNex, there were three aircraft outfitted with atmospheric measurement instruments, a research vessel also carrying atmospheric measurement instruments, and a suite of ground-based instruments (Ryerson et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of mixed layer heights from airborne high spectral resolution lidar, ground-based measurements, and the WRF-Chem model during CalNex and CARES

et al. 2014

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Abstract. The California Research at the Nexus of Air Quality and Climate Change (CalNex) and Carbonaceous Aerosol and Radiative Effects Study (CARES) field campaigns during May and June 2010 provided a data set appropriate for studying the structure of the atmospheric boundary layer (BL). The NASA Langley Research Center (LaRC) airborne high spectral resolution lidar (HSRL) was deployed to California onboard the NASA LaRC B-200 aircraft to aid in characterizing aerosol properties during these two field campaigns. Measurements of aerosol extinction (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm) profiles during 31 flights, many in coordination with other research aircraft and ground sites, constitute a diverse data set for use in characterizing the spatial and temporal distribution of aerosols, as well as the depth and variability of the daytime mixed layer (ML) height. The paper describes the modified Haar wavelet covariance transform method used to derive the ML heights from HSRL backscatter profiles. HSRL ML heights are validated using ML heights derived from two radiosonde profile sites during CARES. Comparisons between ML heights from HSRL and a Vaisala ceilometer operated during CalNex were used to evaluate the representativeness of a fixed measurement over a larger region. In the Los Angeles basin, comparisons of ML heights derived from HSRL measurements and ML heights derived from the ceilometer result in a very good agreement (mean bias difference of 10 m and correlation coefficient of 0.89) up to 30 km away from the ceilometer site, but are essentially uncorrelated for larger distances, indicating that the spatial variability of the ML height is significant over these distances and not necessarily well captured by limited ground stations. The HSRL ML heights are also used to evaluate the performance in simulating the temporal and spatial variability of ML heights from the Weather Research and Forecasting Chemistry (WRF-Chem) community model. When compared to aerosol ML heights from HSRL, thermodynamic ML heights from WRF-Chem were underpredicted in the CalNex and CARES regions, shown by a bias difference value of −157 m and −29 m, respectively. Better agreement over the Central Valley than in mountainous regions suggests that some variability in the ML height is not well captured at the 4 km grid resolution of the model. A small but significant number of cases have poor agreement when WRF-Chem consistently overestimates the ML height in the late afternoon. Additional comparisons with WRFChem aerosol mixed layer heights show no significant improvement over thermodynamic ML heights, confirming that any differences between measurement and model are not due to the methodology of ML height determination.

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Section: Comparison With Ceilometer and Investigation Of Spatial Varimentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Comparison of mixed layer heights from airborne high spectral resolution lidar, ground-based measurements, and the WRF-Chem model during CalNex and CARES

et al. 2014

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“…Chuang et al (2013b) have reported WSOC as high as 25.2% PM 2.5 in Chiangmai, Thailand. By contrast, Duong et al (2011) have reported relatively WSOC as low as 6%-11% of PM 2.5 in the Los Angeles Basin and outflow regions during the 2010 CalNex field campaign. Table 1 also shows WSOC in OC to be 62.8% ± 8.2% and 57.8% ± 15.5% in 2012 and 2013, respectively.…”

Section: Carbonaceous Contentsmentioning

confidence: 94%

Aerosol Chemical Profile of Near-Source Biomass Burning Smoke in Sonla, Vietnam during 7-SEAS Campaigns in 2012 and 2013

Lee

Ram

Nguyen

et al. 2016

Aerosol Air Qual. Res.

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This study aimed to investigate aerosol chemical characteristics and to obtain the chemical profile of near-source biomass burning (BB) aerosols at a site (675 m a.s.l.) in Sonla, Northern Vietnam. Particulate matter (PM) with an aerodynamic diameter less than or equal to 2.5 µm (PM 2.5 ) was collected over a 24 h sampling period as part of the Seven South East Asian Studies (7-SEAS) campaign. The studies were conducted when BB was highly active -that is, in the spring of 2012 and 2013. The collected particles were analyzed for carbonaceous fractions and water-soluble components, in addition to the mass concentration. Data obtained were further analyzed to determine the stable species profile by classifying the 5-day air-mass backward trajectories. The average PM 2.5 mass concentrations were 51 ± 19 µg m -3 and 57 ± 27 µg m -3 in 2012 and 2013, respectively. Carbonaceous contents dominated BB aerosol, with 59% ± 9% and 58% ± 9% in organic carbon (OC) and 9% ± 3% and 10% ± 3% in elemental carbon (EC) of PM 2.5 in 2012 and 2013, respectively. Of the 8 carbonaceous fractions analyzed thermo-optically for PM 2.5 , OC3 (evolution temperature at 280°C-480°C) was most abundant in OC fractions, and EC1-OP (elemental carbon evolved at 580°C minus the pyrolized OC fractions) was predominant in EC fractions in most occasions. Among the measured water-soluble inorganic ions, NH 4 + and SO 4 2-widely varied, indicating the influence of different trajectory origins. This finding was confirmed by trajectory classification of aerosol data. The trajectories were also distinguished with respect to char-EC to soot-EC ratio, and water-soluble OC. These characteristics were highest in the trajectory from the BB source area.

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“…Limits of detection were 0.2 and 1.0 µgm −3 for EC and OC, respectively. Water-soluble organic carbon (WSOC) was measured in PM 2.5 using a particle-into-liquid sampler (PILS, Brechtel Manufacturing Inc.) coupled to a total organic carbon analyzer (TOC; Sievers model 800) (Sullivan et al, 2006; Duong et al, 2011; Wonaschütz et al, 2011). The overall measurement uncertainty associated with the reported WSOC concentrations is estimated to be approximately 10% with a limit of detection of 0.1 µgm −3 .…”

Section: Methodsmentioning

confidence: 99%

On the competition among aerosol number, size and composition in predicting CCN variability: a multi-annual field study in an urbanized desert

et al. 2015

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A 2-year data set of measured CCN (cloud condensation nuclei) concentrations at 0.2 % supersaturation is combined with aerosol size distribution and aerosol composition data to probe the effects of aerosol number concentrations, size distribution and composition on CCN patterns. Data were collected over a period of 2 years (2012–2014) in central Tucson, Arizona: a significant urban area surrounded by a sparsely populated desert. Average CCN concentrations are typically lowest in spring (233 cm−3), highest in winter (430 cm−3) and have a secondary peak during the North American monsoon season (July to September; 372 cm−3). There is significant variability outside of seasonal patterns, with extreme concentrations (1 and 99 % levels) ranging from 56 to 1945 cm−3 as measured during the winter, the season with highest variability. Modeled CCN concentrations based on fixed chemical composition achieve better closure in winter, with size and number alone able to predict 82% of the variance in CCN concentration. Changes in aerosol chemical composition are typically aligned with changes in size and aerosol number, such that hygroscopicity can be parameterized even though it is still variable. In summer, models based on fixed chemical composition explain at best only 41% (pre-monsoon) and 36% (monsoon) of the variance. This is attributed to the effects of secondary organic aerosol (SOA) production, the competition between new particle formation and condensational growth, the complex interaction of meteorology, regional and local emissions and multi-phase chemistry during the North American monsoon. Chemical composition is found to be an important factor for improving predictability in spring and on longer timescales in winter. Parameterized models typically exhibit improved predictive skill when there are strong relationships between CCN concentrations and the prevailing meteorology and dominant aerosol physicochemical processes, suggesting that similar findings could be possible in other locations with comparable climates and geography.

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Water-soluble organic aerosol in the Los Angeles Basin and outflow regions: Airborne and ground measurements during the 2010 CalNex field campaign

Cited by 53 publications

References 68 publications

Comparison of mixed layer heights from airborne high spectral resolution lidar, ground-based measurements, and the WRF-Chem model during CalNex and CARES

Comparison of mixed layer heights from airborne high spectral resolution lidar, ground-based measurements, and the WRF-Chem model during CalNex and CARES

Aerosol Chemical Profile of Near-Source Biomass Burning Smoke in Sonla, Vietnam during 7-SEAS Campaigns in 2012 and 2013

On the competition among aerosol number, size and composition in predicting CCN variability: a multi-annual field study in an urbanized desert

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