The influence of clouds on radical concentrations: observations and modelling studies of HO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; during the Hill Cap Cloud Thuringia (HCCT) campaign in 2010

Whalley, Lisa K.; Stone, Daniel; George, Ingrid; Mertes, Stephan; Pinxteren, Dominik van; Tilgner, Andreas; Herrmann, Hartmut; Evans, M. J.; Heard, Dwayne E.

doi:10.5194/acp-15-3289-2015

Cited by 33 publications

(35 citation statements)

References 39 publications

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“…In the case of the Anchorage based INTEX-B flights, gamma HO 2 was solely responsible for around half the uncertainty in HO 2 mixing ratios. While this sensitivity is not unexpected considering aerosol uptake of HO 2 has been shown to be important in poleward regions (Martin et al, 2003;Mao et al, 2010;Whalley et al, 2015;Christian et al, 2017), we also find considerable sensitivity to this factor in more southerly locations as well (Figs. 6,7,8,and 9).…”

Section: Aerosol Uptakementioning

confidence: 54%

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Global sensitivity analysis of GEOS-Chem modeled ozone and hydrogen oxides during the INTEX campaigns

Christian¹,

Brune²,

Mao³

et al. 2017

Preprint

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For ozone and OH, modeled mixing ratios were most sensitive to a bevy of emissions, notably lightning NO x , various surface NO x sources, and isoprene. HO 2 mixing ratios were most sensitive to CO and isoprene emissions as well as the aerosol uptake of HO 2 . With ozone and OH being generally over predicted by the model, 10 we find better agreement between modeled and measured vertical profiles when reducing NO x emissions from surface as well as lightning sources.

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Section: Aerosol Uptakementioning

confidence: 54%

“…Conversely, the box model may be better matching the measured profile just due to its lack of aerosol uptake of HO 2 . In the Arctic, the aerosol 5 uptake to HO 2 is a major loss pathway for HO 2 (Whalley et al, 2015). Without this loss pathway, the box model may have artificially high HO 2 mixing ratios.…”

mentioning

confidence: 99%

Global sensitivity analysis of GEOS-Chem modeled ozone and hydrogen oxides during the INTEX campaigns

Christian¹,

Brune²,

Mao³

et al. 2017

Preprint

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“…In the case of HO 2 and RO 2 , the radicals were first titrated with NO to OH before FAGE detection. The current mode of operation is described in detail elsewhere (Whalley et al, 2015). The HO 2 observations used as a constraint in the modelling studies reported in Sect.…”

Section: Radical Measurementsmentioning

confidence: 99%

Detailed budget analysis of HONO in central London reveals a missing daytime source

et al. 2016

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Abstract. Measurements of HONO were carried out at an urban background site near central London as part of the Clean air for London (ClearfLo) project in summer 2012. Data were collected from 22 July to 18 August 2014, with peak values of up to 1.8 ppbV at night and non-zero values of between 0.2 and 0.6 ppbV seen during the day. A wide range of other gas phase, aerosol, radiation, and meteorological measurements were made concurrently at the same site, allowing a detailed analysis of the chemistry to be carried out. The peak HONO / NO x ratio of 0.04 is seen at ∼ 02:00 UTC, with the presence of a second, daytime, peak in HONO / NO x of similar magnitude to the night-time peak, suggesting a significant secondary daytime HONO source. A photostationary state calculation of HONO involving formation from the reaction of OH and NO and loss from photolysis, reaction with OH, and dry deposition shows a significant underestimation during the day, with calculated values being close to 0, compared to the measurement average of 0.4 ppbV at midday. The addition of further HONO sources from the literature, including dark conversion of NO 2 on surfaces, direct emission, photolysis of ortho-substituted nitrophenols, the postulated formation from the reaction of HO 2 × H 2 O with NO 2 , photolysis of adsorbed HNO 3 on ground and aerosols, and HONO produced by photosensitized conversion of NO 2 on the surface increases the daytime modelled HONO to 0.1 ppbV, still leaving a significant missing daytime source. The missing HONO is plotted against a series of parameters including NO 2 and OH reactivity (used as a proxy for organic material), with little correlation seen. Much better correlation is observed with the product of these species with j (NO 2 ), in particular NO 2 and the product of NO 2 with OH reactivity. This suggests the missing HONO source is in some way related to NO 2 and also requires sunlight. Increasing the photosensitized surface conversion rate of NO 2 by a factor of 10 to a mean daytime first-order loss of ∼ 6 ×10 −5 s −1 (but which varies as a function of j (NO 2 )) closes the daytime HONO budget at all times (apart from the late afternoon), suggesting that urban surfaces may enhance this photosensitized source. The effect of the missing HONO to OH radical production is also investigated and it is shown that the model needs to be constrained to measured HONO in order to accurately reproduce the OH radical measurements.

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“…Cloud droplets are also beneficial to heterogeneous and aqueous reactions (Notholt et al, 1992;Huijnen et al, 2014;Hoyle et al, 2015). Trace gases and radicals react on the surface or inside of the cloud droplets, leading to changes in the composition of secondary aerosol particles (Weller and Herrmann, 2015;Whalley et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Chemical Composition and Bacterial Community in Size-Resolved Cloud Water at the Summit of Mt. Tai, China

Zhu

Chen

Wang

et al. 2018

Aerosol Air Qual. Res.

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A three-stage collector was used to collect size-resolved cloud samples at the summit of Mt. Tai. Subsequently, analyses of pH values, water-soluble ions, and trace metals were performed and bacterial community were conducted using MiSeq amplicon sequencing. The pH values of the samples decreased as droplet sizes decreased. Sulfate (SO 4 2-), nitrate (NO 3 -) and ammonium (NH 4 + ) were the main secondary inorganic ions which their concentration distributed significantly different from size-resolved cloud water. The NH 4 + concentration was higher in smaller droplets. The SO 4 2-and NO 3 -concentrations were higher in larger droplets. The Ca 2+ concentration increased as droplet size increased. Small droplet samples tended to have lower pH value, mainly because of the more acidic (SO 4 2-and NO 3 -) and less acid-neutralizing (NH 4 + and Ca 2+ ) components. The bacterial community in size-resolved cloud samples were firstly recognized and dominated by the genera of Lactococcus (average abundance 34.9%) and Bacillus (average abundance 34.0%). Linear discriminant analysis effect size (LEfSe) revealed differences of the bacterial community in size-resolved cloud water samples, which was probably caused by the bacterial size. Redundancy analysis suggested several minor correlations that the H 2 O 2 , NO 2 -concentrations, and trace metals exert effects on the bacterial community.

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The influence of clouds on radical concentrations: observations and modelling studies of HO<sub>x</sub> during the Hill Cap Cloud Thuringia (HCCT) campaign in 2010

Cited by 33 publications

References 39 publications

Global sensitivity analysis of GEOS-Chem modeled ozone and hydrogen oxides during the INTEX campaigns

Global sensitivity analysis of GEOS-Chem modeled ozone and hydrogen oxides during the INTEX campaigns

Detailed budget analysis of HONO in central London reveals a missing daytime source

Chemical Composition and Bacterial Community in Size-Resolved Cloud Water at the Summit of Mt. Tai, China

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