Implications of iodine chemistry for daytime HO2 levels at Rishiri Island

Kanaya, Yugo; Yokouchi, Yoko; Matsumoto, Jun; Nakamura, Kenji; Kato, S.; Tanimoto, Hiroshi; Furutani, Hiroshi; Toyota, K.; Akimoto, Hajime

doi:10.1029/2001gl014061

Cited by 48 publications

(68 citation statements)

References 16 publications

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“…This box modelling study is consistent with previous studies (Kanaya et al, 2002(Kanaya et al, , 2007Bloss et al, 2005a;Sommariva et al, 2007;Whalley et al, 2010;Mahajan et al, 2010a;Stone et al, 2012) in that it implies that halogen chemistry is likely to increase the OH concentration of the marine boundary layer (and potentially other regions of the troposphere) as it enhances the HO 2 to OH conversion through the production of HOBr and HOI. We now look at the impact of halogen chemistry on the concentrations of OH and HO 2 at the Cape Verde Atmospheric Observatory within the framework of a global atmospheric chemistry model.…”

Section: Constrained Box Modelsupporting

confidence: 79%

“…This impact of halogen chemistry is consistent in sign and magnitude with previous studies (Kanaya et al, 2002(Kanaya et al, , 2007Bloss et al, 2005a;Sommariva et al, 2006Sommariva et al, , 2007Whalley et al, 2010). Figure 4 shows the mean midday total RO x budget (given the fast processing time between HO 2 and HOBr / HOI we identify the RO x family as OH, HO 2 , HOBr, HOI, RO and RO 2 ) for the two measurement periods during SOS for model runs with and without halogens.…”

Section: Constrained Box Modelsupporting

confidence: 72%

“…In general, observationally constrained box model simulations suggest that halogens in the troposphere will increase OH concentrations, primarily because of a change in the HO 2 to OH ratio occurring as a result of reactions of halogen oxides (XO) with HO 2 to produce a hypohalous acid (HOX) which photolyses to give an OH radical and a halogen atom (Kanaya et al, 2002(Kanaya et al, , 2007Bloss et al, 2005a;Sommariva et al, 2006Sommariva et al, , 2007Whalley et al, 2010). Other impacts on the HO x photochemical system are observed (impacts from changes to NO x chemistry etc.…”

Section: Introductionmentioning

confidence: 99%

“…The role of halogens in HO x chemistry was demonstrated during the NAMBLEX campaign in Mace Head, Ireland , following several studies which attributed box model overestimates of HO 2 observations in marine environments to unmeasured halogen monoxides (Carslaw et al, 1999Kanaya et al, 2001Kanaya et al, , 2002Kanaya et al, , 2007. Simultaneous measurements of OH and HO 2 by laserinduced fluorescence (LIF) (Bloss et al, 2005a;Smith et al, 2006) and halogen species by a combination of DOAS (for BrO or IO, OIO and I 2 ) and broadband cavity ring-down spectroscopy (BBCRDS) (for OIO and I 2 ) (Bitter et al, 2005) during NAMBLEX enabled box model calculations to fully explore the impacts of halogens on the local composition.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of bromine and iodine chemistry on tropospheric OH and HO2: comparing observations with box and global model perspectives

et al. 2018

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Abstract. The chemistry of the halogen species bromine and iodine has a range of impacts on tropospheric composition, and can affect oxidising capacity in a number of ways. However, recent studies disagree on the overall sign of the impacts of halogens on the oxidising capacity of the troposphere. We present simulations of OH and HO 2 radicals for comparison with observations made in the remote tropical ocean boundary layer during the Seasonal Oxidant Study at the Cape Verde Atmospheric Observatory in 2009. We use both a constrained box model, using detailed chemistry derived from the Master Chemical Mechanism (v3.2), and the three-dimensional global chemistry transport model GEOSChem. Both model approaches reproduce the diurnal trends in OH and HO 2 . Absolute observed concentrations are well reproduced by the box model but are overpredicted by the global model, potentially owing to incomplete consideration of oceanic sourced radical sinks. The two models, however, differ in the impacts of halogen chemistry. In the box model, halogen chemistry acts to increase OH concentrations (by 9.8 % at midday at the Cape Verde Atmospheric Observatory), while the global model exhibits a small increase in OH at the Cape Verde Atmospheric Observatory (by 0.6 % at midday) but overall shows a decrease in the global annual mass-weighted mean OH of 4.5 %. These differences reflect the variety of timescales through which the halogens impact the chemical system. On short timescales, photolysis of HOBr and HOI, produced by reactions of HO 2 with BrO and IO, respectively, increases the OH concentration. On longer timescales, halogen-catalysed ozone destruction cycles lead to lower primary production of OH radicals through ozone photolysis, and thus to lower OH concentrations. The global model includes more of the longer timescale responses than the constrained box model, and overall the global impact of the longer timescale response (reduced primary production due to lower O 3 concentrations) overwhelms the shorter timescale response (enhanced cycling from HO 2 to OH), and thus the global OH concentration decreases. The Earth system contains many such responses on a large range of timescales. This work highlights the care that needs to be taken to understand the full impact of any one process on the system as a whole.

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Section: Constrained Box Modelsupporting

confidence: 79%

Section: Constrained Box Modelsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impacts of bromine and iodine chemistry on tropospheric OH and HO2: comparing observations with box and global model perspectives

et al. 2018

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“…In this section we compare observed [HO 2 ] with those calculated using Eq. (5), and a modified form incorporating the reactions of HO 2 with halogen monoxide species and also loss to aerosol, which have been advanced previously as possible explanations for model overpredictions of HO 2 measurements made in the MBL (Kanaya et al, 2002;Sommariva et al, 2004;Haggerstone et al, 2005). Steady state HO 2 calculations were possible on 9 days of the campaign, maximised by using CO-acetylene and CH 4 -propane correlations to fill gaps in CO and CH 4 data.…”

Section: Adding Other Oh Sources and Sinks To The Steady State Expresmentioning

confidence: 99%

Concentrations of OH and HO2 radicals during NAMBLEX: measurements and steady state analysis

et al. 2006

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Abstract. OH and HO 2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×10 5 molecule cm −3 (5 min acquisition period; signal-tonoise ratio = 1). HO 2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×10 6 molecule cm −3 . The diurnal variation of OH was measured on 24 days, and that of HO 2 on 17 days. The local solar noon OH concentrations ranged between (3-8)×10 6 molecule cm −3 , with a 24 h mean concentration of 9.1×10 5 molecule cm −3 . The local solar noon HO 2 concentrations were (0.9-2.1)×10 8 molecule cm −3 (3.5-8.2 pptv), with a 24 h mean concentration of 4.2×10 7 molecule cm −3 (1.6 pptv). HO 2 radicals in the range (2-3)×10 7 molecule cm −3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HO x radicals under primarily clean marine conditions. Steady state expressions are used to calculate OH and HO 2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO 2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly Correspondence to: D. E. Heard (d.e.heard@leeds.ac.uk) over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.

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Direct Measurements of HO_x Radicals in the Marine Boundary Layer: Testing the Current Tropospheric Chemistry Mechanism

Kanaya

Akimoto

2002

The Chemical Record

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OH and HO(2) radicals, atmospheric detergents, and the reservoir thereof, play central roles in tropospheric chemistry. In spite of their importance, we had no choice but to trust their concentrations predicted by modeling studies based on known chemical processes. However, recent direct measurements of these radicals have enabled us to test and revise our knowledge of the processes by comparing the predicted and observed values of the radical concentrations. We developed a laser-induced fluorescence (LIF) instrument and successfully observed OH and HO(2) at three remote islands of Japan (Oki Island, Okinawa Island, and Rishiri Island). At Okinawa Island, the observed daytime level of HO(2) agreed closely with the model estimates, suggesting that the photochemistry at Okinawa is well described by the current chemistry mechanism. At Rishiri Island, in contrast, the observed daytime level of HO(2) was consistently much lower than the calculated values. We proposed that iodine chemistry, usually not incorporated into the mechanism, is at least partly responsible for the discrepancy in the results. At night, HO(2) was detected at levels greater than 1 pptv at all three islands, suggesting the presence of processes in the dark that produce radicals. We showed that ozone reactions with unsaturated hydrocarbons, including monoterpenes, could significantly contribute to radical production.

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Implications of iodine chemistry for daytime HO₂ levels at Rishiri Island

Cited by 48 publications

References 16 publications

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis

Direct Measurements of HO_x Radicals in the Marine Boundary Layer: Testing the Current Tropospheric Chemistry Mechanism

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Implications of iodine chemistry for daytime HO2 levels at Rishiri Island

Cited by 48 publications

References 16 publications

Impacts of bromine and iodine chemistry on tropospheric OH and HO&lt;sub&gt;2&lt;/sub&gt;: comparing observations with box and global model perspectives

Impacts of bromine and iodine chemistry on tropospheric OH and HO&lt;sub&gt;2&lt;/sub&gt;: comparing observations with box and global model perspectives

Concentrations of OH and HO&lt;sub&gt;2&lt;/sub&gt; radicals during NAMBLEX: measurements and steady state analysis

Direct Measurements of HOx Radicals in the Marine Boundary Layer: Testing the Current Tropospheric Chemistry Mechanism

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Implications of iodine chemistry for daytime HO₂ levels at Rishiri Island

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis

Direct Measurements of HO_x Radicals in the Marine Boundary Layer: Testing the Current Tropospheric Chemistry Mechanism