Aerosol Characteristics in the Entrainment Interface Layer In Relation to the Marine Boundary Layer and Free Troposphere

Dadashazar, Hossein; Braun, Rachel A.; Crosbie, Ewan; Chuang, P. Y.; Woods, Roy K.; Jonsson, Haflidi H.; Sorooshian, Armin

doi:10.5194/acp-2017-913

Cited by 10 publications

(13 citation statements)

References 48 publications

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“…Concentrations of N a in the boundary layer tended to be more vertically homogeneous as compared to the FT, owing to more mixing and turbulence, as demonstrated previously for the study region based on aerosol size distribution data (Dadashazar et al, ). More specifically, for the nine soundings exhibiting evidence of BB layers both below and above cloud, the standard deviation of the N a values for the profiles below and above cloud were 165 and 839 cm −3 , respectively.…”

Section: Resultssupporting

confidence: 78%

Biomass Burning Plumes in the Vicinity of the California Coast: Airborne Characterization of Physicochemical Properties, Heating Rates, and Spatiotemporal Features

et al. 2018

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This study characterizes in situ airborne properties associated with biomass burning (BB) plumes in the vicinity of the California coast. Out of 231 total aircraft soundings in July-August 2013 and 2016, 81 were impacted by BB layers. A number of vertical characteristics of BB layers are summarized in this work (altitude, location relative to cloud top height, thickness, number of vertically adjacent layers, interlayer distances) in addition to differences in vertical aerosol concentration profiles due to either surface type (e.g., land or ocean) or time of day. Significant BB layer stratification occurred, especially over ocean versus land, with the majority of layers in the free troposphere and within 100 m of the boundary layer top. Heating rate profiles demonstrated the combined effect of cloud and BB layers and their mutual interactions, with enhanced heating in BB layers with clouds present underneath. Aerosol size distribution data are summarized below and above the boundary layer, with a notable finding being enhanced concentrations of supermicrometer particles in BB conditions. A plume aging case study revealed the dominance of organics in the free troposphere, with secondary production of inorganic and organic species and coagulation as a function of distance from fire source up to 450 km. Rather than higher horizontal and vertical resolution, a new smoke injection height method was the source of improved agreement for the vertical distribution of BB aerosol in the Navy Aerosol Analysis and Prediction System model when compared to airborne data. Key Points: • Significant biomass burning (BB) layer stratification with majority of layers in the free troposphere within 100 m of the boundary layer top • A new smoke injection height method improved agreement for the vertical distribution of BB aerosol in the NAAPS model versus in situ data • Shortwave heating rate profiles demonstrate the combined effect of stratocumulus cloud and BB layers and their mutual interactions Supporting Information:• Supporting Information S1• Data Set S1

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Section: Resultssupporting

confidence: 78%

Biomass Burning Plumes in the Vicinity of the California Coast: Airborne Characterization of Physicochemical Properties, Heating Rates, and Spatiotemporal Features

et al. 2018

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“…The AC-OAL is operationally defined as the narrow altitude band (generally <200 m) directly above the marine stratocumulus cloud decks where OA mass loadings were relatively large (>1.5 μg m −3 ) and a distinct AC-OAL PMF factor contributed >80% of total OA mass ( Figure S6 ). This region occupies a similar location as the commonly referenced entrainment interface layer (EIL) above cloud decks ( Dadashazar et al, 2018 ; Wood, 2012 ), but is defined by the aerosol characteristics described above rather than by turbulence and buoyancy characteristics, as is common for the EIL ( Carman et al, 2012 ). Median aerosol properties are reported in Tables 1 – 3 for each of these three regions, while Figure 2 displays vertical profiles of aerosol and meteorological properties.…”

Section: Resultsmentioning

confidence: 99%

“…Median aerosol number concentrations observed in the MBL (754 cm −3 ) exceeded those in the FT (333 cm −3 ), as expected. Observed particle concentrations were maximized within the AC-OAL (1,662 cm −3 ), where intense actinic fluxes and elevated concentrations of the hydroxyl radical may drive new particle formation ( Dadashazar et al, 2018 ; Mauldin et al, 1999 ). For all measured SS > 0.1%, observed CCN concentrations were also largest within the AC-OAL, rather than the MBL or FT, underscoring the importance of understanding the hygroscopicity of above-cloud CCN-active particles ( Coggon et al, 2014 ; Sorooshian, Lu, et al, 2007 ; Sorooshian et al, 2007 ; Wang et al, 2008 ).…”

Section: Resultsmentioning

confidence: 99%

“…Aerosol and cloud droplet number concentrations were characterized using a variety of instruments, including multiple condensation particle counters (CPC, TSI 3010, D p > 10 nm; ultrafine CPC, TSI UFCPC, D p > 3 nm), a passive cavity aerosol spectrometer probe (PCASP, D p ~0.11–3.4 μm), and forward scattering spectrometer probe (FSSP, Particle Measuring Systems [PMS], D p ~1.6–45 μm). Cloud liquid water content was measured using a PVM-100A probe ( Gerber et al, 1994 ), and a threshold value of 0.02 g m −3 was used to distinguish in-cloud sampling ( Dadashazar et al, 2018 ; MacDonald et al, 2018 ).…”

Section: Methodsmentioning

confidence: 99%

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Characterization of Aerosol Hygroscopicity Over the Northeast Pacific Ocean: Impacts on Prediction of CCN and Stratocumulus Cloud Droplet Number Concentrations

Schulze

Charan

Kenseth

et al. 2020

Earth and Space Science

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During the Marine Aerosol Cloud and Wildfire Study (MACAWS) in June and July of 2018, aerosol composition and cloud condensation nuclei (CCN) properties were measured over the N.E. Pacific to characterize the influence of aerosol hygroscopicity on predictions of ambient CCN and stratocumulus cloud droplet number concentrations (CDNC). Three vertical regions were characterized, corresponding to the marine boundary layer (MBL), an above-cloud organic aerosol layer (AC-OAL), and the free troposphere (FT) above the AC-OAL. The aerosol hygroscopicity parameter (κ) was calculated from CCN measurements (κ CCN) and bulk aerosol mass spectrometer (AMS) measurements (κ AMS). Within the MBL, measured hygroscopicities varied between values typical of both continental environments (~0.2) and remote marine locations (~0.7). For most flights, CCN closure was achieved within 20% in the MBL. For five of the seven flights, assuming a constant aerosol size distribution produced similar or better CCN closure than assuming a constant "marine" hygroscopicity (κ = 0.72). An aerosol-cloud parcel model was used to characterize the sensitivity of predicted stratocumulus CDNC to aerosol hygroscopicity, size distribution properties, and updraft velocity. Average CDNC sensitivity to accumulation mode aerosol hygroscopicity is 39% as large as the sensitivity to the geometric median diameter in this environment. Simulations suggest CDNC sensitivity to hygroscopicity is largest in marine stratocumulus with low updraft velocities (<0.2 m s −1), where accumulation mode particles are most relevant to CDNC, and in marine stratocumulus or cumulus with large updraft velocities (>0.6 m s −1), where hygroscopic properties of the Aitken mode dominate hygroscopicity sensitivity.

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“…While Table shows the obvious result that N a values are much higher above cloud in BB conditions 2,400 cm 3 (95% confidence interval, 1,518–3,363 cm 3 ) versus non‐BB conditions 202 cm 3 (110–294 cm 3 ), an important result is that BB conditions also yielded much higher N a values below cloud 912 cm 3 (415–1,725 cm 3 ) versus 123 cm −3 (73–180 cm −3 ). Thus, primary activation of subcloud CCN into cloud droplets is not limited to aerosols emitted within the MBL but rather can be entrained from the FT as documented in several past works (e.g., Capaldo et al, ; Clarke et al, ; Dadashazar et al, ; Katoshevski et al, ; Wood et al, ). Past work has examined how the variation in subcloud aerosol number concentration is related to parameters such as the gradient of CCN number concentration between vertical layers above and below cloud, boundary layer depth, and the time passed since aerosol and cloud layer have come into contact (e.g., Diamond et al, ; Wood et al, ).…”

Section: Resultsmentioning

confidence: 79%

Effects of Biomass Burning on Stratocumulus Droplet Characteristics, Drizzle Rate, and Composition

et al. 2019

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This study reports on airborne measurements of stratocumulus cloud properties under varying degrees of influence from biomass burning (BB) plumes off the California coast. Data are reported from five total airborne campaigns based in Marina, California, with two of them including influence from wildfires in different areas along the coast of the western United States. The results indicate that subcloud cloud condensation nuclei number concentration and mass concentrations of important aerosol species (organics, sulfate, nitrate) were better correlated with cloud droplet number concentration (N d ) as compared to respective above-cloud aerosol data. Given that the majority of BB particles resided above cloud tops, this is an important consideration for future work in the region as the data indicate that the subcloud BB particles likely were entrained from the free troposphere. Lower cloud condensation nuclei activation fractions were observed for BB-impacted clouds as compared to non-BB clouds due, at least partly, to less hygroscopic aerosols. Relationships between N d and either droplet effective radius or drizzle rate are preserved regardless of BB influence, indicative of how parameterizations can exhibit consistent skill for varying degrees of BB influence as long as N d is known. Lastly, the composition of both droplet residual particles and cloud water changed significantly when clouds were impacted by BB plumes, with differences observed for different fire sources stemming largely from effects of plume aging time and dust influence. Coggon, M. M., Aghdam, M. A., et al. (2019). Effects of biomass burning on stratocumulus droplet characteristics, drizzle rate, and composition.

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Aerosol Characteristics in the Entrainment Interface Layer In Relation to the Marine Boundary Layer and Free Troposphere

Cited by 10 publications

References 48 publications

Biomass Burning Plumes in the Vicinity of the California Coast: Airborne Characterization of Physicochemical Properties, Heating Rates, and Spatiotemporal Features

Biomass Burning Plumes in the Vicinity of the California Coast: Airborne Characterization of Physicochemical Properties, Heating Rates, and Spatiotemporal Features

Characterization of Aerosol Hygroscopicity Over the Northeast Pacific Ocean: Impacts on Prediction of CCN and Stratocumulus Cloud Droplet Number Concentrations

Effects of Biomass Burning on Stratocumulus Droplet Characteristics, Drizzle Rate, and Composition

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