scholarly journals Peroxy radical observations over West Africa during the AMMA 2006 campaign: Photochemical activity in episodes of formation of convective systems on the basis of radical measurements

2009 ◽  
Vol 9 (1) ◽  
pp. 1585-1619 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Kartal ◽  
L. Reichert ◽  
J. P. Burrows ◽  
J. Meyer Arnek ◽  
...  
Keyword(s):  
West Africa ◽  
Biomass Burning ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Back Trajectory ◽  
Peroxy Radicals ◽  
Air Masses ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Multidisciplinary Analysis

Abstract. Peroxy radical measurements made on board the DLR-Falcon research aircraft over West Africa within the African Monsoon Multidisciplinary Analysis (AMMA) campaign during the 2006 wet monsoon are presented in this study. The analysis of data focuses on the photochemical activity of air masses sampled during episodes of intense convection and biomass burning. Generally, the total sum of peroxy radical mixing ratios, measured in the outflow of convective clouds, are quite variable but occasionally are coupled with the NO variations indicating the coexistence, or simultaneously emission of NOx, with a potential radical precursor (i.e., formaldehyde, acetone or peroxides) which has likely been transported to higher atmospheric layers. Based on the measurements, significant O3 production rates up to 2 ppb/h in the MCS outflow are estimated by using a box model with simplified chemistry. Peroxy radicals having mixing ratios around 20–25 pptv and with peak values of up to 60–70 pptv are measured within biomass burning plumes, detected at the coast in Ghana. Calculations of back-trajectory densities confirm the origin of these air masses being a biomass burning region at southern latitudes and close to the Gulf of Guinea, according to satellite pictures. Measured peroxy radical concentrations agree reasonably with modelled estimations taking into account simple local chemistry. Moreover the vertical profiles taken at the aircraft base in Ouagadougou, Burkina Faso, indicate the common feature of having maximum concentrations between 2 and 4 km, in agreement with other literature values obtained under similar conditions.

scholarly journals Peroxy radical observations over West Africa during AMMA 2006: photochemical activity in the outflow of convective systems

2009 ◽  
Vol 9 (11) ◽  
pp. 3681-3695 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Kartal ◽  
L. Reichert ◽  
J. P. Burrows ◽  
J. Meyer Arnek ◽  
...  
Keyword(s):  
West Africa ◽  
Biomass Burning ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Back Trajectory ◽  
Peroxy Radicals ◽  
Air Masses ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Multidisciplinary Analysis

Abstract. Peroxy radical measurements made on board the DLR-Falcon research aircraft over West Africa within the African Monsoon Multidisciplinary Analysis (AMMA) campaign during the 2006 wet monsoon are presented in this study. The analysis of data focuses on the photochemical activity of air masses sampled during episodes of intense convection and biomass burning. Generally, the total sum of peroxy radical mixing ratios, measured in the outflow of convective clouds, are quite variable but occasionally are coupled with the NO variations indicating the coexistence or simultaneous emission of NOx, with a potential radical precursor (i.e. formaldehyde, acetone or peroxides), which has likely been transported to higher atmospheric altitudes. Based on the measurements, significant O3 production rates around 1 ppb/h in the MCS outflow are estimated by using a box model with simplified chemistry. Peroxy radicals having mixing ratios around 20–25 pptv and with peak values of up to 60–70 pptv are measured within biomass burning plumes, detected at the coast in Ghana. Calculations of back-trajectory densities confirm the origin of these air masses being a biomass burning region at southern latitudes and close to the Gulf of Guinea, according to satellite pictures. Measured peroxy radical concentrations agree reasonably with modelled estimations taking into account simple local chemistry. Moreover, the vertical profiles taken at the aircraft base in Ouagadougou, Burkina Faso, indicate the common feature of having maximum concentrations between 2 and 4 km, in agreement with other literature values obtained under similar conditions.

Comparison of Airborne Peroxy Radical Measurements with MECO(n) model simulation during EMeRGe in Europe

2020 ◽  
Author(s):  
Yangzhuoran Liu ◽  
Mariano Mertens ◽  
Maria Dolores Andrés Hernández ◽  
Midhun George ◽  
Vladyslav Nenakhov ◽  
...  
Keyword(s):  
Climate Model ◽  
Model Simulation ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Peroxy Radicals ◽  
Transport And Transformation ◽  
Air Masses ◽  
Mixing Ratios ◽  
Airborne Measurement ◽  
On Line

<p>Observations of tropospheric peroxy radicals are a key point for interpretation of the processing and transformation of polluted outflows from major populated centres (MPCs). A series of European MPCs are investigated by the project EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales). With this objective two airborne campaigns using the research platform HALO (High Altitude and LOng range aircraft) were carried out over Europe in summer 2017 and over east Asia in the intermonsoon period in 2018. The Institute of Environmental Physics (IUP) in Bremen (Germany) participated in both EMeRGe campaigns with the airborne measurement of the total sum of peroxy radicals, RO<sub>2</sub><sup>*</sup>, by using  the home made PeRCEAS instrument based on the combination of the PERCA (peroxy radical chemical amplification)  and CRDS (cavity ring down spectroscopy) techniques. One of the main purposes of the campaigns was the investigation of the characteristics and chemical transformation of MPC outflows at the local and regional scales.</p><p>During the EMeRGe campaign in Europe, air masses of different photochemical activity were measured, where RO<sub>2</sub><sup>*</sup> mixing ratios up to 100pptv being observed. In the present study the RO<sub>2</sub><sup>* </sup>observations for six measurement flights of EMeRGe in Europe have been compared with RO<sub>2</sub> (here defined as the sum of HO<sub>2 </sub>+ CH<sub>3</sub>O<sub>2 </sub>+ ISOOH + CH<sub>3</sub>CO<sub>3 </sub>+ CH<sub>3</sub>COCH<sub>2</sub>O<sub>2</sub>) simulated by using the MECO(n) model.</p><p>MECO(n) (MESSy-fied ECHAM and COSMO models nested n times), is  a global/regional chemistry-climate model developed by the MESSy consortium, which couples on-line the global chemistry-climate model EMAC with the regional chemistry-climate model COSMO-CLM/MESSy. The same anthropogenic emission inventory (EDGAR 4.3.1) as well as the same solver for chemical kinetics, involving complex tropospheric and stratospheric chemistry, are applied in EMAC and COSMO-CLM/MESSy.</p><p>Overall, the agreement between the measurements and model is reasonable for RO<sub>2</sub><sup>* </sup>observations below 40 pptv. Events with higher mixing ratios seem not to be well reproduced by the model but underestimated. Further details on the modelling and the result of the comparison will be presented.</p>

Investigation of the photochemical activity in different MPC outflows during EMeRGe

2020 ◽  
Author(s):  
Midhun George ◽  
Maria Dolores Andrés Hernández ◽  
Yangzhuoran Liu ◽  
Vladyslav Nenakhov ◽  
John Philip Burrows ◽  
...  
Keyword(s):  
East Asia ◽  
Peroxy Radical ◽  
Photochemical Activity ◽  
Peroxy Radicals ◽  
Essential Information ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Photolysis Rates ◽  
Order Of Magnitude

<p>Since peroxy radicals are closely involved in a number of tropospheric chemical processes like O<sub>3</sub> budget, hydrocarbon oxidation and acid formation, the accurate measurement of these radicals can provide essential information to improve our understanding of processing and transformation of polluted outflows from megacities and Major Population Centres (MPCs).</p><p>Airborne measurements of the total sum of peroxy radicals, RO<sub>2</sub>*  = HO<sub>2</sub> + ∑ RO<sub>2</sub>, where R is an organic group, were conducted in Europe in summer 2017 and in East Asia in spring 2018 within the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) project by using the PeRCEAS instrument (Peroxy Radical Chemical Enhancement and Absorption Spectrometer), on board of the HALO research aircraft (www.halo.dlr.de).</p><p>Over the course of both measurement campaigns different MPC outflows were investigated including among others, London, Rome, Manila and Taipei. Polluted air masses of different origin and composition were probed. Overall the peroxy radical mixing ratios were of the same order of magnitude in the air masses probed in Europe and in East Asia. The variations in the photochemical activity were studied by taking into account simultaneous observations of radical precursors and photolysis rates, while applying known oxidation mechanisms. Radical precursors, photolysis rates and aerosol load were generally higher in Asia, which might indicate higher radical loss reactions on the aerosol surface than in Europe. Moreover this study shows a clear deviation in the photostationary state for MPC outflows close to the emission sources. Based on this information, this presentation will focus on the actual understanding of the photochemical processing in the probed air masses.</p>

scholarly journals Diel peroxy radicals in a semi industrial coastal area: nighttime formation of free radicals

2012 ◽  
Vol 12 (8) ◽  
pp. 19529-19570 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Kartal ◽  
J. N. Growley ◽  
V. Sinha ◽  
E. Regelin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Trace Gases ◽  
Peroxy Radical ◽  
Industrial Area ◽  
Diurnal Variations ◽  
Peroxy Radicals ◽  
Industrial Emissions ◽  
Air Masses ◽  
Volatile Organic ◽  
Organic Trace

Abstract. Peroxy radicals were measured by a PeRCA (Peroxy Radical Chemical Amplifier) instrument in the boundary layer during the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) campaign at a coastal, forested site influenced by urban-industrial emissions in Southern Spain in late autumn. Total peroxy radicals (RO2* = HO2 + ΣRO2) generally showed a daylight maximum between 10 and 50 pptv at 13:00 UTC, with an average of 18 pptv over the 15 days of measurements. Emissions from the industrial area of Huelva often impacted the measurement site at night during the campaign. The processing of significant levels of anthropogenic organics leads to an intense nocturnal radical chemistry accompanied by formation of organic peroxy radicals at comparable levels to those of summer photochemical conditions with peak events up to 60–80 pptv. The RO2 production initiated by reactions of NO3 with organic trace gases was estimated to be significant but not sufficient to account for the concentrations of RO2* observed in air masses carrying high pollutant loading. The nocturnal production of peroxy radicals seems therefore to be dominated by ozonolysis of volatile organic compounds. RO2* diurnal variations were consistent with other HO2 measurements available at the site. HO2/RO2* ratios generally varied between 0.3 and 0.4 in all wind directions. Occasional HO2/RO2* ≥ 1 seemed to be associated with periods of high RO2* variability and with RO2 interferences in the HO2 measurement in air masses with high RO2 load.

Trace gases and organic aerosol at a rural site in Vietnam during large scale biomass burning

2021 ◽  
Author(s):  
Simone M. Pieber ◽  
Dac-Loc Nguyen ◽  
Hendryk Czech ◽  
Stephan Henne ◽  
Nicolas Bukowiecki ◽  
...  
Keyword(s):  
Air Quality ◽  
Chemical Composition ◽  
Biomass Burning ◽  
Large Scale ◽  
Trace Gases ◽  
Organic Aerosol ◽  
Trace Gas ◽  
Rural Site ◽  
Air Masses ◽  
Mixing Ratios

<p>Open biomass burning (BB) is a globally widespread phenomenon. The fires release pollutants, which are harmful for human and ecosystem health and alter the Earth's radiative balance. Yet, the impact of various types of BB on the global radiative forcing remains poorly constrained concerning greenhouse gas emissions, BB organic aerosol (OA) chemical composition and related light absorbing properties. Fire emissions composition is influenced by multiple factors (e.g., fuel and thereby vegetation-type, fuel moisture, fire temperature, available oxygen). Due to regional variations in these parameters, studies in different world regions are needed. Here we investigate the influence of seasonally recurring BB on trace gas concentration and air quality at the regional Global Atmosphere Watch (GAW) station Pha Din (PDI) in rural Northwestern Vietnam. PDI is located in a sparsely populated area on the top of a hill (1466 m a.s.l.) and is well suited to study the large-scale fires on the Indochinese Peninsula, whose pollution plumes are frequently transported towards the site [1]. We present continuous trace gas observations of CO<sub>2</sub>, CH<sub>4</sub>, CO, and O<sub>3</sub> conducted at PDI since 2014 and interpret the data with atmospheric transport simulations. Annually recurrent large scale BB leads to hourly time-scale peaks CO mixing ratios at PDI of 1000 to 1500 ppb around every April since the start of data collection in 2014. We complement this analysis with carbonaceous PM<sub>2.5 </sub>chemical composition analyzed during an intensive campaign in March-April 2015. This includes measurements of elemental and organic carbon (EC/OC) and more than 50 organic markers, such as sugars, PAHs, fatty acids and nitro-aromatics [2]. For the intensive campaign, we linked CO, CO<sub>2</sub>, CH<sub>4</sub> and O<sub>3</sub> mixing ratios to a statistical classification of BB events, which is based on OA composition. We found increased CO and O<sub>3</sub> levels during medium and high BB influence during the intensive campaign. A backward trajectory analysis confirmed different source regions for the identified periods based on the OA cluster. Typically, cleaner air masses arrived from northeast, i.e., mainland China and Yellow sea during the intensive campaign. The more polluted periods were characterized by trajectories from southwest, with more continental recirculation of the medium cluster, and more westerly advection for the high cluster. These findings highlight that BB activities in Northern Southeast Asia significantly enhances the regional OA loading, chemical PM<sub>2.5 </sub>composition and the trace gases in northwestern Vietnam. The presented analysis adds valuable data on air quality in a region of scarce data availability.</p><p> </p><p><strong>REFERENCES</strong></p><p>[1] Bukowiecki, N. et al. Effect of Large-scale Biomass Burning on Aerosol Optical Properties at the GAW Regional Station Pha Din, Vietnam. AAQR. 19, 1172–1187 (2019).</p><p>[2] Nguyen, D. L, et al. Carbonaceous aerosol composition in air masses influenced by large-scale biomass burning: a case-study in Northwestern Vietnam. ACPD., https://doi.org/10.5194/acp-2020-1027, in review, 2020.</p>

scholarly journals Peroxy radical partitioning during the AMMA radical intercomparison exercise

2010 ◽  
Vol 10 (21) ◽  
pp. 10621-10638 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Stone ◽  
D. M. Brookes ◽  
R. Commane ◽  
C. E. Reeves ◽  
...  
Keyword(s):  
Trace Gases ◽  
Geographical Area ◽  
Peroxy Radical ◽  
Peroxy Radicals ◽  
Intercomparison Exercise ◽  
Additional Information ◽  
Multidisciplinary Analysis ◽  
Photolysis Rates ◽  
Photolysis Frequencies ◽  
Wing Tip

Abstract. Peroxy radicals were measured onboard two scientific aircrafts during the AMMA (African Monsoon Multidisciplinary Analysis) campaign in summer 2006. This paper reports results from the flight on 16 August 2006 during which measurements of HO2 by laser induced fluorescence spectroscopy at low pressure (LIF-FAGE) and total peroxy radicals (RO2* = HO2+ΣRO2, R = organic chain) by two similar instruments based on the peroxy radical chemical amplification (PeRCA) technique were subject of a blind intercomparison. The German DLR-Falcon and the British FAAM-BAe-146 flew wing tip to wing tip for about 30 min making concurrent measurements on 2 horizontal level runs at 697 and 485 hPa over the same geographical area in Burkina Faso. A full set of supporting measurements comprising photolysis frequencies, and relevant trace gases like CO, NO, NO2, NOy, O3 and a wider range of VOCs were collected simultaneously. Results are discussed on the basis of the characteristics and limitations of the different instruments used. Generally, no data bias are identified and the RO2* data available agree quite reasonably within the instrumental errors. The [RO2*]/[HO2] ratios, which vary between 1:1 and 3:1, as well as the peroxy radical variability, concur with variations in photolysis rates and in other potential radical precursors. Model results provide additional information about dominant radical formation and loss processes.

scholarly journals Evidence of the impact of deep convection on reactive Volatile Organic Compounds in the upper tropical troposphere during the AMMA experiment in West Africa

2010 ◽  
Vol 10 (21) ◽  
pp. 10321-10334 ◽  
Author(s):  
J. Bechara ◽  
A. Borbon ◽  
C. Jambert ◽  
A. Colomb ◽  
P. E. Perros
Keyword(s):  
Volatile Organic Compounds ◽  
West Africa ◽  
Organic Compounds ◽  
Deep Convection ◽  
Cloud Base ◽  
Convective Conditions ◽  
Air Masses ◽  
Convective Systems ◽  
Volatile Organic ◽  
The Impact

Abstract. A large dataset of reactive trace gases was collected for the first time over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) field experiment in August 2006. Volatile Organic Compounds (VOC from C5–C9) were measured onboard the two French aircrafts the ATR-42 and the Falcon-20 by a new instrument AMOVOC (Airborne Measurement Of Volatile Organic Compounds). The goal of this study is (i) to characterize VOC distribution in the tropical region of West Africa (ii) to determine the impact of deep convection on VOC distribution and chemistry in the tropical upper troposphere (UT) and (iii) to characterize its spatial and temporal extensions. Experimental strategy consisted in sampling at altitudes between 0 and 12 km downwind of Mesoscale Convective Systems (MCS) and at cloud base. Biogenic and anthropogenic VOC distribution in West Africa is clearly affected by North to South emission gradient. Isoprene, the most abundant VOC, is at maximum level over the forest (1.26 ppb) while benzene reaches its maximum over the urban areas (0.11 ppb). First, a multiple physical and chemical tracers approach using CO, O3 and relative humidity was implemented to distinguish between convective and non-convective air masses. Then, additional tools based on VOC observations (tracer ratios, proxy of emissions and photochemical clocks) were adapted to characterize deep convection on a chemical, spatial and temporal basis. VOC vertical profiles show a "C-shaped" trend indicating that VOC-rich air masses are transported from the surface to the UT by deep convective systems. VOC mixing ratios in convective outflow are up to two times higher than background levels even for reactive and short-lived VOC (e.g. isoprene up to 0.19 ppb at 12 km-altitude) and are dependent on surface emission type. As a consequence, UT air mass reactivity increases from 0.52 s−1 in non-convective conditions to 0.95 s−1 in convective conditions. Fractions of boundary layer air contained in convective outflow are estimated to be 40 ± 15%. Vertical transport timescale is calculated to be 25 ± 10 min between 0 to 12 km altitude. These results characterize deep convection occurring over West Africa and provide relevant information for tropical convection parameterization in regional/global models.

scholarly journals Ozone budget in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) campaign

2009 ◽  
Vol 9 (2) ◽  
pp. 6979-7032
Author(s):  
M. Saunois ◽  
C. E. Reeves ◽  
C. Mari ◽  
J. G. Murphy ◽  
D. J. Stewart ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Troposphere ◽  
Atmospheric Measurements ◽  
Air Masses ◽  
African Monsoon ◽  
Mixing Ratios ◽  
Budget Analysis ◽  
Multidisciplinary Analysis ◽  
Ozone Maximum ◽  
Research Aircraft

Abstract. A bi-dimensional latitudinal-vertical meterological model coupled with O3-NOx-VOC chemistry is used to reproduce the distribution of ozone and precursors in the boundary layer over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) campaign as observed on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft. The model reproduces the increase of ozone mixing ratios in the boundary layer observed between the forested region south of 13° N and the Sahelian area northward. Sensitivity and budget analysis reveals that the intertropical convergence zone is a moderate source of O3 rich-air in the boundary layer due to convective downdrafts. Dry deposition drives the ozone minimum over the vegetated area. The combination of high NOx emissions from soil north of 13° N and northward advection by the monsoon flux of VOC-enriched air masses contributes to the ozone maximum simulated at higher latitudes. Simulated OH exhibit a well marked latitudinal gradient with minimum concentrations over the vegetated region where the reactions with biogenic compounds predominate. The model underestimates the observed OH mixing ratios, however this model discrepancy has slight effect on ozone budget and does not alter the conclusions.

scholarly journals Two years of Ozone radio soundings over Cotonou as part of AMMA: overview

2009 ◽  
Vol 9 (3) ◽  
pp. 11221-11268 ◽  
Author(s):  
V. Thouret ◽  
M. Saunois ◽  
A. Minga ◽  
A. Mariscal ◽  
B. Sauvage ◽  
...  
Keyword(s):  
West Africa ◽  
Biomass Burning ◽  
Lower Stratosphere ◽  
Lower Troposphere ◽  
Data Sets ◽  
Wet Season ◽  
Data Set ◽  
In Situ Data ◽  
Multidisciplinary Analysis ◽  
First Time

Abstract. As part of the African Monsoon Multidisciplinary Analysis (AMMA) program, a total of 98 ozone vertical profiles over Cotonou, Benin, have been measured during a 26 month period (December 2004–January 2007). These regular measurements broadly document the seasonal and inter annual variability of ozone in both the troposphere and the lower stratosphere over West Africa for the first time. This data set is complementary to the MOZAIC observations made from Lagos between 0 and 12 km during the period 1998–2004. Both data sets highlight the unique way in which West Africa is impacted by two biomass burning seasons: in December–February (dry season) due to burning in the Sahelian band and in June–August (wet season) due to burning in southern Africa. High inter annual variabilities between Cotonou and Lagos data sets and within each data set are observed and are found to be a major characteristic of this region. In particular, the dry and wet seasons are discussed in order to set the data of the Special Observing Periods (SOPs) into a climatological context. Compared to other dry and wet seasons, the dry and wet season campaigns took place in rather high ozoneenvironments. During the sampled wet seasons, southern intrusions of biomass burning were particularly frequent with concentrations up to 120 ppbv of ozone in the lower troposphere. An insight into the ozone distribution in the upper troposphere and the lower stratosphere (up to 26 km) is given. The first tropospheric columns of ozone based on in-situ data in this region are assessed. They compare well with satellite products on seasonal and inter annual time-scales, provided that the layer below 850 Pa where the remote instrument is less sensitive to ozone, is removed.

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