scholarly journals Gaseous chemistry and aerosol mechanism developments for version 3.5.1 of the online regional model, WRF-Chem

2014 ◽  
Vol 7 (6) ◽  
pp. 2557-2579 ◽  
Author(s):  
S. Archer-Nicholls ◽  
D. Lowe ◽  
S. Utembe ◽  
J. Allan ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Reduced Form ◽  
Sea Spray ◽  
Wind Fields ◽  
Aerosol Composition ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
The Impact ◽  
Phase Chemical

Abstract. We have made a number of developments to the Weather, Research and Forecasting model coupled with Chemistry (WRF-Chem), with the aim of improving model prediction of trace atmospheric gas-phase chemical and aerosol composition, and of interactions between air quality and weather. A reduced form of the Common Reactive Intermediates gas-phase chemical mechanism (CRIv2-R5) has been added, using the Kinetic Pre-Processor (KPP) interface, to enable more explicit simulation of VOC degradation. N2O5 heterogeneous chemistry has been added to the existing sectional MOSAIC aerosol module, and coupled to both the CRIv2-R5 and existing CBM-Z gas-phase schemes. Modifications have also been made to the sea-spray aerosol emission representation, allowing the inclusion of primary organic material in sea-spray aerosol. We have worked on the European domain, with a particular focus on making the model suitable for the study of nighttime chemistry and oxidation by the nitrate radical in the UK atmosphere. Driven by appropriate emissions, wind fields and chemical boundary conditions, implementation of the different developments are illustrated, using a modified version of WRF-Chem 3.4.1, in order to demonstrate the impact that these changes have in the Northwest European domain. These developments are publicly available in WRF-Chem from version 3.5.1 onwards.

scholarly journals Gaseous chemistry and aerosol mechanism developments for version 3.5.1 of the online regional model, WRF-Chem

2014 ◽  
Vol 7 (1) ◽  
pp. 871-929 ◽  
Author(s):  
S. Archer-Nicholls ◽  
D. Lowe ◽  
S. Utembe ◽  
J. Allan ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Atmospheric Composition ◽  
Reduced Form ◽  
Sea Spray ◽  
North West ◽  
The North ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
The Impact

Abstract. We have made a number of developments to the Weather, Research and Forecasting model coupled with Chemistry (WRF-Chem), with the aim of making the model more suitable for prediction of atmospheric composition and of interactions between air quality and weather. We have worked on the European domain, with a particular focus on making the model suitable for the study of nighttime chemistry and oxidation by the nitrate radical in the UK atmosphere. A reduced form of the Common Reactive Intermediates gas-phase chemical mechanism (CRIv2-R5) has been added, using the Kinetic Pre-Processor (KPP) interface, to enable more explicit simulation of VOC degradation. N2O5 heterogeneous chemistry has been added to the existing sectional MOSAIC aerosol module, and coupled to both the CRIv2-R5 and existing CBM-Z gas-phase schemes. Modifications have also been made to the sea-spray aerosol emission representation, allowing the inclusion of primary organic material in sea-spray aerosol. Driven by appropriate emissions, wind fields and chemical boundary conditions, implementation of the different developments are illustrated, using a modified version of WRF-Chem 3.4.1, in order to demonstrate the impact that these changes have in the North-West European domain. These developments are publicly available in WRF-Chem from version 3.5.1 onwards.

scholarly journals Formation of secondary aerosols: impact of the gas-phase chemical mechanism

2010 ◽  
Vol 10 (8) ◽  
pp. 20625-20672
Author(s):  
Y. Kim ◽  
K. Sartelet ◽  
C. Seigneur
Keyword(s):  
Gas Phase ◽  
Transport Model ◽  
Model Performance ◽  
Organic Aerosols ◽  
Chemical Kinetic ◽  
Chemical Mechanism ◽  
Chemical Components ◽  
The Impact ◽  
Phase Chemical ◽  
Inorganic And Organic

Abstract. The impact of two recent gas-phase chemical kinetic mechanisms (CB05 and RACM2) on the formation of secondary inorganic and organic aerosols is compared for simulations of PM2.5 over Europe between 15 July and 15 August 2001. The host chemistry transport model is Polair3D of the Polyphemus air-quality platform. Particulate matter is modeled with SIREAM, which is coupled to the thermodynamic model ISORROPIA and to the secondary organic aerosol module MAEC. Model performance is satisfactory with both mechanisms for speciated PM2.5. The monthly-mean difference of the concentration of PM2.5 is less than 1 μg/m3 (6%) over the entire domain. Secondary chemical components of PM2.5 include sulfate, nitrate, ammonium and organic aerosols, and the chemical composition of PM2.5 is not significantly different between the two mechanisms. Monthly-mean concentrations of inorganic aerosol are higher with RACM2 than with CB05 (+16% for sulfate, +11% for nitrate, and +12% for ammonium), whereas the concentrations of organic aerosols are slightly higher with CB05 than with RACM2 (+26% for anthropogenic SOA and +1% for biogenic SOA). Differences in the inorganic and organic aerosols result primarily from differences in oxidant concentrations (OH, O3 and NO3). Nitrate formation tends to be HNO3-limited over land and differences in the concentrations of nitrate are due to differences in concentration of HNO3. Differences in aerosols formed from aromatics SVOC are due to different aromatics oxidation between CB05 and RACM2. The aromatics oxidation in CB05 leads to more cresol formation, which then leads to more SOA. Differences in the aromatics aerosols would be significantly reduced with the recent CB05-TU mechanism for toluene oxidation. Differences in the biogenic aerosols are due to different oxidant concentrations (monoterpenes) and different particulate organic mass concentrations affecting the gas-particle partitioning of SOA (isoprene).

scholarly journals Evaluating the sensitivity of fine particulate matter (PM<sub>2.5</sub>) simulations to chemical mechanism in Delhi

2020 ◽  
Author(s):  
Chinmay Jena ◽  
Sachin D. Ghude ◽  
Rachana Kulkarni ◽  
Sreyashi Debnath ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Gas Phase ◽  
Optical Depth ◽  
Fine Particulate Matter ◽  
Chemical Mechanism ◽  
Aerosol Composition ◽  
Gangetic Plain ◽  
Fine Particulate ◽  
Phase Chemical

Abstract. Elevated levels of fine particulate matter (PM2.5) during winter-time have become one of the most important environmental concerns over the Indo-Gangetic Plain (IGP) region of India, and particularly for Delhi. Accurate reconstruction of PM2.5, its optical properties, and dominant chemical components over this region is essential to evaluate the performance of the air quality models. In this study, we investigated the effect of three different aerosol mechanisms coupled with gas-phase chemical schemes on simulated PM2.5 mass concentration in Delhi using the Weather Research and Forecasting model with the Chemistry module (WRF-Chem). The model was employed to cover the entire northern region of India at 10 km horizontal spacing. Results were compared with comprehensive filed data set on dominant PM2.5 chemical compounds from the Winter Fog Experiment (WiFEX) at Delhi, and surface PM2.5 observations in Delhi (17 sites), Punjab (3 sites), Haryana (4 sites), Uttar Pradesh (7 sites) and Rajasthan (17 sites). The Model for Ozone and Related Chemical Tracers (MOZART-4) gas-phase chemical mechanism coupled with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) aerosol scheme (MOZART-GOCART) were selected in the first experiment as it is currently employed in the operational air quality forecasting system of Ministry of Earth Sciences (MoES), Government of India. Other two simulations were performed with the MOZART-4 gas-phase chemical mechanism coupled with the Model for Simulating Aerosol Interactions and Chemistry (MOZART-MOSAIC), and Carbon Bond 5 (CB-05) gas-phase mechanism couple with the Modal Aerosol Dynamics Model for Europe/Secondary Organic Aerosol Model (CB05-MADE/SORGAM) aerosol mechanisms. The evaluation demonstrated that chemical mechanisms affect the evolution of gas-phase precursors and aerosol processes, which in turn affect the optical depth and overall performance of the model for PM2.5. All the three coupled schemes, MOZART-GOCART, MOZART-MOSAIC, and CB05-MADE/SORGAM, underestimate the observed concentrations of major aerosol composition (NO3−, SO42−, Cl−, BC, OC, and NH4+) and precursor gases (HNO3, NH3, SO2, NO2, and O3) over Delhi. Comparison with observations suggests that the simulations using MOZART-4 gas-phase chemical mechanism with MOSAIC aerosol performed better in simulating aerosols over Delhi and its optical depth over the IGP. The lowest NMB (−18.8 %, MB = −27.4 μg/m3) appeared for the simulations using MOZART-MOSAIC scheme, whereas the NMB was observed 32.5 % (MB = −47.5 μg/m3) for CB05-MADE/SORGAM and −53.3 % (MB = −78 μg/m3) for MOZART-GOCART scheme.

scholarly journals Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments

2016 ◽  
Author(s):  
Sara D. Forestieri ◽  
Gavin C. Cornwell ◽  
Taylor M. Helgestad ◽  
Kathryn A. Moore ◽  
Christopher Lee ◽  
...  
Keyword(s):  
Light Scattering ◽  
Relative Humidity ◽  
Salt Content ◽  
Sea Salt ◽  
Sea Spray ◽  
Hygroscopic Growth ◽  
Phytoplankton Blooms ◽  
Aerosol Composition ◽  
Sea Spray Aerosol ◽  
Indoor And Outdoor

Abstract. The extent to which water uptake influences the light scattering ability of marine sea spray aerosol (SSA) particles depends critically on SSA chemical composition. The organic fraction of SSA can increase during phytoplankton blooms, decreasing the salt content and therefore the hygroscopicity of the particles. In this study, subsaturated hygroscopic growth factors at 85 % relative humidity (GF(85 %)) of SSA particles were quantified during two induced phytoplankton blooms in marine aerosol reference tanks (MARTs). One MART was illuminated with fluorescent lights and the other was illuminated with sunlight, referred to as the "indoor" and "outdoor" MARTs, respectively. GF(85 %) values for SSA particles were derived from measurements of light scattering and particle size distributions, concurrently with online single particle and bulk aerosol composition measurements. During both microcosm experiments, the observed bulk average GF(85 %) values were depressed substantially relative to pure, inorganic sea salt, by 10 to 19 %, with a one (indoor MART) and six (outdoor MART) day lag between GF(85 %) depression and the peak chlorophyll-a concentrations. The fraction of organiccontaining SSA particles generally increased after the peak of the phytoplankton blooms. The GF(85 %) values were inversely correlated with the fraction of particles containing organic or other biological markers. This indicates these particles were less hygroscopic than the particles identified as predominately sea salt containing and demonstrates a clear relationship between SSA particle composition and the sensitivity of light scattering to variations in relative humidity. The implications of these observations to the direct climate effects of SSA particles are discussed.

scholarly journals Radicals in the marine boundary layer during NEAQS 2004: a model study of day-time and night-time sources and sinks

2009 ◽  
Vol 9 (9) ◽  
pp. 3075-3093 ◽  
Author(s):  
R. Sommariva ◽  
H. D. Osthoff ◽  
S. S. Brown ◽  
T. S. Bates ◽  
T. Baynard ◽  
...  
Keyword(s):  
Boundary Layer ◽  
New England ◽  
Gas Phase ◽  
Marine Boundary Layer ◽  
Peroxy Radical ◽  
Chemical Mechanism ◽  
Physical Parameters ◽  
Peroxy Radicals ◽  
Night Time ◽  
Aerosol Composition

Abstract. This paper describes a modelling study of several HOx and NOx species (OH, HO2, organic peroxy radicals, NO3 and N2O5) in the marine boundary layer. A model based upon the Master Chemical Mechanism (MCM) was constrained to observations of chemical and physical parameters made onboard the NOAA ship R/V Brown as part of the New England Air Quality Study (NEAQS) in the summer of 2004. The model was used to calculate [OH] and to determine the composition of the peroxy radical pool. Modelled [NO3] and [N2O5] were compared to in-situ measurements by Cavity Ring-Down Spectroscopy. The comparison showed that the model generally overestimated the measurements by 30–50%, on average. The model results were analyzed with respect to several chemical and physical parameters, including uptake of NO3 and N2O5 on fog droplets and on aerosol, dry deposition of NO3 and N2O5, gas-phase hydrolysis of N2O5 and reactions of NO3 with NMHCs and peroxy radicals. The results suggest that fog, when present, is an important sink for N2O5 via rapid heterogeneous uptake. The comparison between the model and the measurements were consistent with values of the heterogeneous uptake coefficient of N2O5 (γN2O5)>1×10−2, independent of aerosol composition in this marine environment. The analysis of the different loss processes of the nitrate radical showed the important role of the organic peroxy radicals, which accounted for a significant fraction (median: 15%) of NO3 gas-phase removal, particularly in the presence of high concentrations of dimethyl sulphide (DMS).

Modelling the photochemical formation of high H2O2 concentrations and secondary sulfate observed during winter haze periods in the NCP

2020 ◽  
Author(s):  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Lin He ◽  
Bernd Heinold ◽  
Can Ye ◽  
...  
Keyword(s):  
Air Pollution ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Photochemical Reactions ◽  
Data Availability ◽  
Phase Reaction ◽  
Aerosol Composition ◽  
Chemistry Research ◽  
The Impact

&lt;p&gt;During winter, the North China Plain (NCP) is frequently characterized by severe haze conditions connected with extremely high PM2.5 and NOx concentrations, i.e. strong air pollution. The NCP is one of the most populated regions worldwide where haze periods have direct health effects. Tropospheric haze particles are a complex multiphase and multi-component environment, in which multiphase chemical processes are able to alter the chemical aerosol composition and deduced physical aerosol properties and can strongly contribute to air pollution. Despite many past investigations, the chemical haze processing is still uncertain and represents a challenge to atmospheric chemistry research. Recent NCP studies during autumn/winter 2017 haze periods have revealed unexpected high H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; concentrations of about 1&amp;#160;ppb suggesting H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; as a potential contributor to secondary PM2.5 mass, e.g., due to sulfur(IV) oxidation. However, the multiphase H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formation under such NOx concentrations is still unclear. Therefore, the present study aimed at the examination of potential multiphase H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formation pathways, and the feedback on sulfur oxidation.&lt;/p&gt;&lt;p&gt;Multiphase chemistry simulations of a measurement campaign in the NCP are performed with the box model SPACCIM. The multiphase chemistry model within SPACCIM contains the gas-phase mechanism MCMv3.2 and the aqueous-phase mechanism CAPRAM4.0 together with both its aromatics module CAPRAM-AM1.0 and its halogen module CAPRAM-HM2.1. Furthermore, based on available literature data, the multiphase chemistry mechanism is extended considering further multiphase formation pathways of HONO and an advanced HOx mechanism scheme enabling higher in-situ H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formations in haze particles. The simulations have been performed for three periods characterized by high H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; concentrations, high RH and PM2.5 conditions and high measurement data availability. Several sensitivity runs have been performed examining the impact of the soluble transition metal ion (TMI) content on the predicted H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formation.&lt;/p&gt;&lt;p&gt;Simulations with the improved multiphase chemistry mechanism shows a good agreement of the modelled H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; concentrations with field data. The modelled H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; concentration shows a substantial dependency on the soluble TMI content. Higher soluble TMI contents result in higher H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; concentrations demonstrating the strong influence of TMI chemistry in haze particles on H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formation. The analysis of the chemical production and sink fluxes reveals that a huge fraction of the multiphase HO&lt;sub&gt;2&lt;/sub&gt; radicals and nearly all of the subsequently formed reaction product H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; is produced in-situ within the haze particles and does not origin from the gas phase. Further chemical analyses show that, during the morning hours, the aqueous-phase reaction of H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; with S(IV) contributes considerably to S(VI) formation beside the HONO related formation of sulfuric acid by OH in the gas-phase.&lt;/p&gt;&lt;p&gt;Finally, a parameterization was developed to study the particle-phase H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; formations as potential source with the global model ECHAM-HAMMOZ. The performed global modelling identifies an increase of gas-phase H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; by a factor of 2.8 through the newly identified particle chemistry. Overall, the study demonstrated that photochemical reactions of HULIS and TMIs in particles are an important H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; source leading to increased particle sulfate formation.&lt;/p&gt;

scholarly journals Effect of primary organic sea spray emissions on cloud condensation nuclei concentrations

2012 ◽  
Vol 12 (1) ◽  
pp. 89-101 ◽  
Author(s):  
D. M. Westervelt ◽  
R. H. Moore ◽  
A. Nenes ◽  
P. J. Adams
Keyword(s):  
Surface Tension ◽  
Southern Ocean ◽  
Source Function ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Sea Salt ◽  
Sea Spray ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
Surfactant Effects

Abstract. This work estimates the primary marine organic aerosol global emission source and its impact on cloud condensation nuclei (CCN) concentrations by implementing an organic sea spray source function into a series of global aerosol simulations. The source function assumes that a fraction of the sea spray emissions, depending on the local chlorophyll concentration, is organic matter in place of sea salt. Effect on CCN concentrations (at 0.2% supersaturation) is modeled using the Two-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled to the GISS II-prime general circulation model. The presence of organics affects CCN activity in competing ways: by reducing the amount of solute available in the particle and decreasing surface tension of CCN. To model surfactant effects, surface tension depression data from seawater samples taken near the Georgia coast were applied as a function of carbon concentrations. A global marine organic aerosol emission rate of 17.7 Tg C yr−1 is estimated from the simulations. Marine organics exert a localized influence on CCN(0.2%) concentrations, decreasing regional concentrations by no more than 5% and by less than 0.5% over most of the globe, assuming direct replacement of sea salt aerosol with organic aerosol. The decrease in CCN concentrations results from the fact that the decrease in particle solute concentration outweighs the organic surfactant effects. The low sensitivity of CCN(0.2%) to the marine organic emissions is likely due to the small compositional changes: the mass fraction of OA in accumulation mode aerosol increases by only ~15% in a biologically active region of the Southern Ocean. To test the sensitivity to uncertainty in the sea spray emissions process, we relax the assumption that sea spray aerosol number and mass remain fixed and instead can add to sea spray emissions rather than replace existing sea salt. In these simulations, we find that marine organic aerosol can increase CCN by up to 50% in the Southern Ocean and 3.7% globally during the austral summer. This vast difference in CCN impact highlights the need for further observational exploration of the sea spray aerosol emission process as well as evaluation and development of model parameterizations.

Gas-phase chemical mechanism compression strategies: Treatment of reactants

1996 ◽  
Vol 30 (6) ◽  
pp. 831-842 ◽  
Author(s):  
P.A. Makar ◽  
W.R. Stockwell ◽  
S.M. Li
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Phase Chemical
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