Urban aerosol chemistry at a land–water  transition site during summer – Part 2:  Aerosol pH and liquid water content

Abstract. Particle acidity (aerosol pH) is an important driver of atmospheric chemical processes and the resulting effects on human and environmental health. Understanding the factors that control aerosol pH is critical when enacting control strategies targeting specific outcomes. This study characterizes aerosol pH at a land–water transition site near Baltimore, MD, during summer 2018 as part of the second Ozone Water-Land Environmental Transition Study (OWLETS-2) field campaign. Inorganic fine-mode aerosol composition, gas-phase NH3 measurements, and all relevant meteorological parameters were used to characterize the effects of temperature, aerosol liquid water (ALW), and composition on predictions of aerosol pH. Temperature, the factor linked to the control of NH3 partitioning, was found to have the most significant effect on aerosol pH during OWLETS-2. Overall, pH varied with temperature at a rate of −0.047 K−1 across all observations, though the sensitivity was −0.085 K−1 for temperatures > 293 K. ALW had a minor effect on pH, except at the lowest ALW levels (< 1 µg m−3), which caused a significant increase in aerosol acidity (decrease in pH). Aerosol pH was generally insensitive to composition (SO42-, SO42-:NH4+, total NH3 (Tot-NH3) = NH3 + NH4+), consistent with recent studies in other locations. In a companion paper, the sources of episodic NH3 events (95th percentile concentrations, NH3 > 7.96 µg m−3) during the study are analyzed; aerosol pH was higher by only ∼ 0.1–0.2 pH units during these events compared to the study mean. A case study was analyzed to characterize the response of aerosol pH to nonvolatile cations (NVCs) during a period strongly influenced by primary Chesapeake Bay emissions. Depending on the method used, aerosol pH was estimated to be either weakly (∼ 0.1 pH unit change based on NH3 partitioning calculation) or strongly (∼ 1.4 pH unit change based on ISORROPIA thermodynamic model predictions) affected by NVCs. The case study suggests a strong pH gradient with size during the event and underscores the need to evaluate assumptions of aerosol mixing state applied to pH calculations. Unique features of this study, including the urban land–water transition site and the strong influence of NH3 emissions from both agricultural and industrial sources, add to the understanding of aerosol pH and its controlling factors in diverse environments.

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Urban aerosol chemistry at a land-water transition site during summer – Part 2: Aerosol pH and liquid water content

10.5194/acp-2021-368 ◽

2021 ◽

Author(s):

Michael A. Battaglia Jr. ◽

Nicholas Balasus ◽

Katherine Ball ◽

Vanessa Caicedo ◽

Ruben Delgado ◽

...

Keyword(s):

Liquid Water ◽

Control Strategies ◽

Liquid Water Content ◽

Companion Paper ◽

Minor Effect ◽

Aerosol Composition ◽

Unit Change ◽

Need To Evaluate ◽

Land Water

Abstract. Particle acidity (aerosol pH) is an important driver of atmospheric chemical processes and the resulting effects on human and environmental health. Understanding the factors that control aerosol pH is critical when enacting control strategies targeting specific outcomes. This study characterizes aerosol pH at a land-water transition site near Baltimore, MD during summer 2018 as part of the second Ozone Water-Land Environmental Transition Study (OWLETS-2) field campaign. Inorganic fine mode aerosol composition, gas-phase NH3 measurements, and all relevant meteorological parameters were used to characterize the effects of temperature, aerosol liquid water (ALW), and composition on predictions of aerosol pH. Temperature, the factor linked to the control of NH3 partitioning, was found to have the most significant effect on aerosol pH during OWLETS-2. Overall, pH varied with temperature at a rate of −0.047 K−1 across all observations, though the sensitivity was −0.085 K−1 for temperatures > 293 K. ALW had a minor effect on pH, except at the lowest ALW levels (< 1 µg m−3) which caused a significant increase in aerosol acidity (decrease in pH). Aerosol pH was generally insensitive to composition (SO42− , SO42−:NH4+ , Tot-NH3 = NH3 + NH4+), consistent with recent studies in other locations. In a companion paper, the sources of episodic NH3 events (95th percentile concentrations, NH3 > 7.96 µg m−3) during the study are analyzed; aerosol pH was higher by only ~0.1–0.2 pH units during these events compared to the study mean. A case study was analyzed to characterize the response of aerosol pH to nonvolatile cations (NVCs) during a period strongly influenced by primary Chesapeake Bay emissions. Depending on the method used, aerosol pH was estimated to be either weakly (~0.1 pH unit change based on NH3 partitioning calculation) or strongly (~1.4 pH unit change based on ISORROPIA thermodynamic model predictions) affected by NVCs. The case study suggests a strong pH gradient with size during the event and underscores the need to evaluate assumptions of aerosol mixing state applied to pH calculations. Unique features of this study, including the urban land-water transition site and the strong influence of NH3 emissions from both agricultural and industrial sources, add to the understanding of aerosol pH and its controlling factors in diverse environments.

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PISTE: A Snow-Physics Model Incorporating Human Factors for Groomed Ski Slopes*

Journal of Hydrometeorology ◽

10.1175/jhm-d-14-0013.1 ◽

2014 ◽

Vol 15 (6) ◽

pp. 2429-2445 ◽

Cited By ~ 3

Author(s):

Rosie Howard ◽

Roland Stull

Keyword(s):

Boundary Conditions ◽

Water Content ◽

Liquid Water ◽

Initial Conditions ◽

Weather Prediction ◽

Liquid Water Content ◽

Snow Surface ◽

Sophisticated Model ◽

Physics Model

Abstract Accurately calculating snow-surface temperature and liquid water content for a groomed ski run, known as a ski piste, is crucial to the preparation of fast skis for alpine racing. Ski technicians can use forecasts of these variables to reduce ski–snow friction by applying layers of wax ahead of time. A new one-dimensional numerical Lagrangian snowpack model, Prognostic Implementation for Snow Temperature Estimation (PISTE), is presented that solves the heat-, liquid water–, and ice-budget equations to calculate these snow variables. In addition, the human effects of skiing and grooming are modeled. Meteorological measurements from a 5-day, clear-sky case study at a ski piste on Whistler Mountain, British Columbia, Canada, are prescribed to PISTE as boundary conditions. Because of a lack of interior snowpack measurements, PISTE was spun up from a dry, isothermal snowpack using repeated boundary conditions from 1 day of measurements. Initial conditions for the main model run that used the subsequent 4 days were taken from this spinup. Simulated and measured snow-surface temperatures show very good agreement, with slight cold daytime and warm nighttime biases (averaging 0.5° and 1°C, respectively). The modeled behavior of snowpack temperature and liquid water content profiles is consistent with previous literature having similar radiative boundary conditions. The case study indicates that PISTE is useful under simple conditions. It shows the potential to be developed into a more sophisticated model that can incorporate complex boundary conditions such as cloudiness and precipitation and can be driven by numerical weather prediction output.

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A case study on the determination of fog optical depth and liquid water path using AVHRR data and relations to fog liquid water content and horizontal visibility

International Journal of Remote Sensing ◽

10.1080/01431169508954416 ◽

1995 ◽

Vol 16 (3) ◽

pp. 515-530 ◽

Cited By ~ 17

Author(s):

J. BENDIX

Keyword(s):

Water Content ◽

Optical Depth ◽

Liquid Water ◽

Liquid Water Content ◽

Liquid Water Path ◽

Horizontal Visibility ◽

Water Path ◽

Avhrr Data

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Supplementary material to "Urban aerosol chemistry at a land-water transition site during summer – Part 2: Aerosol pH and liquid water content"

10.5194/acp-2021-368-supplement ◽

2021 ◽

Author(s):

Michael A. Battaglia Jr. ◽

Nicholas Balasus ◽

Katherine Ball ◽

Vanessa Caicedo ◽

Ruben Delgado ◽

...

Keyword(s):

Water Content ◽

Liquid Water ◽

Liquid Water Content ◽

Urban Aerosol ◽

Aerosol Chemistry ◽

Supplementary Material ◽

Land Water

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Interactions between aerosol organic components and liquid water content during haze episodes in Beijing

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-12163-2019 ◽

2019 ◽

Vol 19 (19) ◽

pp. 12163-12174 ◽

Cited By ~ 10

Author(s):

Xiaoxiao Li ◽

Shaojie Song ◽

Wei Zhou ◽

Jiming Hao ◽

Douglas R. Worsnop ◽

...

Keyword(s):

Real Time ◽

Liquid Water ◽

Liquid Water Content ◽

Organic Fraction ◽

Aerosol Composition ◽

The Real ◽

Volume Fractions ◽

Organic Components ◽

Wide Range ◽

Haze Formation

Abstract. Aerosol liquid water (ALW) is ubiquitous in ambient aerosol and plays an important role in the formation of both aerosol organics and inorganics. To investigate the interactions between ALW and aerosol organics during haze formation and evolution, ALW was modelled based on long-term measurement of submicron aerosol composition in different seasons in Beijing. ALW contributed by aerosol inorganics (ALWinorg) was modelled by ISORROPIA II, and ALW contributed by organics (ALWorg) was estimated with κ-Köhler theory, where the real-time hygroscopicity parameter of the organics (κorg) was calculated from the real-time organic oxygen-to-carbon ratio (O∕C). Overall particle hygroscopicity (κtotal) was computed by weighting component hygroscopicity parameters based on their volume fractions in the mixture. We found that ALWorg, which is often neglected in traditional ALW modelling, contributes a significant fraction (18 %–32 %) to the total ALW in Beijing. The ALWorg fraction is largest on the cleanest days when both the organic fraction and κorg are relatively high. The large variation in O∕C, from 0.2 to 1.3, indicates the wide variety of organic components. This emphasizes the necessity of using real-time κorg, instead of fixed κorg, to calculate ALWorg in Beijing. The significant variation in κorg (calculated from O∕C), together with highly variable organic or inorganic volume fractions, leads to a wide range of κtotal (between 0.20 and 0.45), which has a great impact on water uptake. The variation in organic O∕C, or derived κorg, was found to be influenced by temperature (T), ALW, and aerosol mass concentrations, among which T and ALW both have promoting effects on O∕C. During high-ALW haze episodes, although the organic fraction decreases rapidly, O∕C and derived κorg increase with the increase in ALW, suggesting the formation of more soluble organics via heterogeneous uptake or aqueous processes. A positive feedback loop is thus formed: during high-ALW episodes, increasing κorg, together with decreasing particle organic fraction (or increasing particle inorganic fraction), increases κtotal, and thus further promotes the ability of particles to uptake water.

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Development and Evaluation of In-Flight Icing Index Forecast for Aviation

10.5194/egusphere-egu21-15497 ◽

2021 ◽

Author(s):

Cyril Morcrette ◽

Katie Bennett ◽

Rebecca Bowyer ◽

Philip Gill ◽

Dan Suri

Keyword(s):

Relative Humidity ◽

Liquid Water ◽

Cloud Cover ◽

Liquid Water Content ◽

Model Data ◽

The United Kingdom ◽

Weather Model ◽

Operational Index ◽

Cloud Liquid Water Content

<p>Hindcasts from the United Kingdom Met Office weather model are used as inputs to an in-flight icing index from the literature. This index uses information about model-predicted temperature, relative humidity, vertical velocity and cloud liquid water content. Parts of the icing index formulation are then modified slightly, in the light of comparisons between hindcast model data and ground-based remote sensing observations. Firstly, the link to relative humidity is replaced with a link to model-predicted cloud cover. Secondly, although super-cooled liquid water icing is due to cloud condensate in the liquid phase, the model may not always correctly partition its condensate into the correct phase. So the second modification is to consider all condensate irrespective of phase when calculating the icing index. The skill of the original and new index are then assessed quantitatively against satellite-derived icing potential. We show that the new indices have substantially better reliability than the operational index used up until recently. Finally, we present a case study, when icing was reported, and discuss ways of presenting the likelihood and severity information.</p>

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Pollution based real time control strategies for combined sewer systems

Water Science & Technology ◽

10.2166/wst.1997.0688 ◽

1997 ◽

Vol 36 (8-9) ◽

pp. 331-336 ◽

Cited By ~ 8

Author(s):

Gabriela Weinreich ◽

Wolfgang Schilling ◽

Ane Birkely ◽

Tallak Moland

Keyword(s):

Real Time ◽

Control Strategies ◽

Ammonia Nitrogen ◽

Simple Extension ◽

Real Time Control ◽

Time Control ◽

Sewer Systems ◽

Receiving Waters ◽

Tunnel System

This paper presents results from an application of a newly developed simulation tool for pollution based real time control (PBRTC) of urban drainage systems. The Oslo interceptor tunnel is used as a case study. The paper focuses on the reduction of total phosphorus Ptot and ammonia-nitrogen NH4-N overflow loads into the receiving waters by means of optimized operation of the tunnel system. With PBRTC the total reduction of the Ptot load is 48% and of the NH4-N load 51%. Compared to the volume based RTC scenario the reductions are 11% and 15%, respectively. These further reductions could be achieved with a relatively simple extension of the operation strategy.

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