scholarly journals The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo

2011 ◽  
Vol 366 (1582) ◽  
pp. 3177-3195 ◽  
Author(s):  
A. R. MacKenzie ◽  
B. Langford ◽  
T. A. M. Pugh ◽  
N. Robinson ◽  
P. K. Misztal ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Oil Palm ◽  
Oxidation Products ◽  
Atmospheric Composition ◽  
Additional Contribution ◽  
Mixing Ratios ◽  
Oil Palm Plantation ◽  
Industrial Oil ◽  
High Concentrations

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.

scholarly journals Sensitivity of tropospheric chemical composition to halogen-radical chemistry using a fully coupled size-resolved multiphase chemistry/global climate system – Part 1: Halogen distributions, aerosol composition, and sensitivity of climate-relevant gases

2013 ◽  
Vol 13 (3) ◽  
pp. 6067-6129 ◽  
Author(s):  
M. S. Long ◽  
W.C. Keene ◽  
R. C. Easter ◽  
R. Sander ◽  
X. Liu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Tropospheric Chemistry ◽  
Oxidation Products ◽  
Aerosol Composition ◽  
Mixing Ratios

Abstract. Observations and model studies suggest a significant but highly non-linear role for halogens, primarily Cl and Br, in multiphase atmospheric processes relevant to tropospheric chemistry and composition, aerosol evolution, radiative transfer, weather, and climate. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was tested using a size-resolved multiphase coupled chemistry/global climate model (National Center for Atmospheric Research's Community Atmosphere Model (CAM); v3.6.33). Simulation results showed strong meridional and vertical gradients in Cl and Br species. The simulation reproduced most available observations with reasonable confidence permitting the formulation of potential mechanisms for several previously unexplained halogen phenomena including the enrichment of Br− in submicron aerosol, and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile Br mixing ratios were generally high in the troposphere. Br in the stratosphere was lower than observed due to the lack of long-lived organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrated a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, and non-methane hydrocarbons (NMHC's) to halogen cycling. Simulated O3 and NOx were globally lower (65% and 35%, respectively, less in the planetary boundary layer based on median values) in simulations that included halogens. Globally, little impact was seen in SO2 and non-sea-salt SO42− processing due to halogens. Significant regional differences were evident: the lifetime of nss-SO42− was extended downwind of large sources of SO2. The burden and lifetime of DMS (and its oxidation products) were lower by a factor of 5 in simulations that included halogens, versus those without, leading to a 20% reduction in nss-SO42− in the Southern Hemisphere planetary boundary layer based on median values.

scholarly journals Driving Factors for Isoprene-Surface Ozone and Carbon Dioxide Chemistry Over an Oil Palm plantation in Malaysia

2020 ◽  
Author(s):  
mohd shahrul mohd nadzir ◽  
Maggie Chel Gee Ooi ◽  
Neil RP Harris ◽  
Conor Bolas ◽  
Sherin Hassan Bran ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Chemistry ◽  
Oil Palm ◽  
Meteorological Factors ◽  
Surface Ozone ◽  
Crop Damage ◽  
Palm Tree ◽  
Mixing Ratios ◽  
Oil Palm Plantation

Abstract Background: Biogenic Volatile Organic Compounds (BVOCs) such as isoprene (C5H8) are ozone (O3) precursors that can be emitted at significant concentrations from the oil palm tree (Elaeis guineensis). Reactions involving BVOCs can lead to increased levels of surface O3 which can significantly impair air quality and cause crop damage. This study focuses on the link between isoprene, surface O3 and carbon dioxide (CO2) over an oil palm plantation and the effects of meteorological factors such as temperature and irradiance on the gas concentrations. The mixing ratios of isoprene, surface O3 and CO2 were measured using a portable gas chromatograph with a photoionization detector called ‘iDirac’, an EcoTech O3 analyser, and LI-COR, respectively. Atmospheric models were used for measured selected gases estimation and validation purposes.Results: Results showed that isoprene and surface O3 had maximum daytime mixing ratios of ~25 ppb and ~57 ppb, respectively. CO2 mixing ratios were high during the night compared to the day, with a maximum night-time ratio of ~883 ppm. It is also showed that suppression of isoprene emissions from plants by high CO2 concentrations during the night was due to the reduction of dimethylallyl diphosphate (DMADP) in the leaf cells. The meteorological parameters temperature and light intensity were significantly correlated with isoprene and surface O3, with r2=0.91 and p<0.01 and r2=0.87 and p<0.01, respectively. The Model of Emissions of Gases and Aerosol from Nature (MEGAN) estimated emission rates of isoprene from the oil palm plantation are in the range ~5000 to ~7000 μgm-2 h-1 which are higher than previous studies on pristine forest. This information together with the the in-situ measurement information on isoprene emission flux is then fed into the WRF-CMAQ atmospheric chemistry model to study the effect of oil palm plantation expansion over the years (2000 – 2016) on the local atmospheric chemistry.Conclusions: The in-situ of isoprene measurement in oil palm plantation has provided the variations of atmospheric concentration at different time scale which is important in giving information of surface O3 production. The relationship between isoprene-surface O3 and CO2-isoprene were interconnected at different time and influenced by meteorological factors. The model has discovered regions that are converted into oil palm plantation has experienced rise in isoprene concentration in region that are converted into oil palm plantation, and it even can be carried downwind up to 100 km inland of the emission source.

scholarly journals Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling

2008 ◽  
Vol 8 (4) ◽  
pp. 14033-14085 ◽  
Author(s):  
D. Taraborrelli ◽  
M. G. Lawrence ◽  
T. M. Butler ◽  
R. Sander ◽  
J. Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Oxidation Mechanism ◽  
Tropospheric Chemistry ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Good Representation ◽  
Chemical Production ◽  
Global Models ◽  
Mixing Ratios ◽  
Isoprene Oxidation

Abstract. We present an oxidation mechanism of intermediate size for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended as the second version of the well-established Mainz Isoprene Mechanism (MIM). Our aim is to improve the representation of tropospheric chemistry in regional and global models under all NOx regimes. We evaluate MIM2 and re-evaluate MIM through comparisons with MCM v3.1. We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios. Unlike MIM, MIM2 produces small relative biases for NOx and organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates (RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative biases with respect to hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), methanol (CH3OH), formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids (HCOOH and CH3C(O)OH), being always below ≈6% in all NOx scenarios studied. Most of the isoprene oxidation products are represented explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal. MIM2 is mass-conserving with respect to carbon, including CO2 as well. Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources, as well as for studies focused on the carbon cycle. Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO), propene (CH2=CHCH3) and glyoxal (CHOCHO) with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively. Our new mechanism is expected to substantially improve the results of atmospheric chemistry models by more accurately representing the interplay between atmospheric chemistry, transport and deposition, especially of nitrogen reservoir species. MIM2 allows regional and global models to easily incorporate new experimental results on the chemistry of organic species.

scholarly journals OH and HO<sub>2</sub> radical chemistry in a midlatitude forest: Measurements and model comparisons

2019 ◽  
Author(s):  
Michelle L. Lew ◽  
Pamela S. Rickly ◽  
Brandon P. Bottorff ◽  
Sofia Sklaveniti ◽  
Thierry Léonardis ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Global Climate ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Peroxy Radicals ◽  
Mixing Ratios ◽  
Photolysis Rates ◽  
Model Predictions ◽  
Ho2 Radical

Abstract. Reactions of the hydroxyl (OH) and peroxy radicals (HO2 and RO2) play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of nitrogen oxides (NOx) have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. During the summer of 2015, OH and HO2 radical concentrations as well as total OH reactivity were measured using Laser-Induced Fluorescence - Fluorescence Assay by Gas Expansion (LIF-FAGE) techniques as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area near the Indiana University, Bloomington campus characterized by high mixing ratios of isoprene and low mixing ratios of NOx. Supporting measurements of photolysis rates, VOCs, NOx, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM). Using an OH chemical scavenger technique, the study revealed the presence of an interference with the LIF-FAGE measurements of OH that increased with both ambient concentrations of ozone and temperature. Subtraction of the interference resulted in measured OH concentrations that were in better agreement with model predictions, although the model still underestimated the measured concentrations, likely due to an underestimation of the concentration of NO at this site. Measurements of HO2 radical concentrations during the campaign included a fraction of isoprene-based peroxy radicals (HO2* = HO2 + αRO2) and were found to agree with model predictions. On average, the measured reactivity was consistent with that calculated from measured OH sinks to within 20 %, with modeled oxidation products accounting for the missing reactivity, although significant missing reactivity (approximately 40 % of the total measured reactivity) was observed on some days.

scholarly journals High concentrations of N<sub>2</sub>O<sub>5</sub> and NO<sub>3</sub> observed in daytime with a TD-CIMS: chemical interference or a real atmospheric phenomenon?

2013 ◽  
Vol 6 (4) ◽  
pp. 7473-7504
Author(s):  
X. Wang ◽  
T. Wang ◽  
C. Yan ◽  
Y. J. Tham ◽  
L. Xue ◽  
...  
Keyword(s):  
Hong Kong ◽  
Atmospheric Chemistry ◽  
Thermal Dissociation ◽  
Measurement Techniques ◽  
Urban Site ◽  
Ionization Mass ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
High Concentrations ◽  
Interference Tests

Abstract. Dinitrogen pentoxide (N2O5) and the nitrate radical (NO3) play important roles in atmospheric chemistry, yet accurate measurements of their concentrations remain challenging. A thermal dissociation chemical ionization mass spectrometer (TD-CIMS) was deployed to an urban site in Hong Kong to measure the sum of N2O5 and NO3 in autumn 2010. To our surprise, very high concentrations of N2O5 + NO3 were frequently observed in daytime, with mixing ratios in the range of 200–1000 pptv. To investigate this unusual phenomenon, various interference tests and measurements with different instrument configuration were conducted. It was found that peroxy acetyl nitrate (PAN) contributed to measurable signals at 62 amu, and more importantly, this interference increased significantly with co-existence of NO2. Nitric acid (HNO3), on the other hand, had little interference to the detection of N2O5/NO3 via the NO3− ion in our TD-CIMS. According to the test results, the interference from PAN and NO2 could have contributed to 30–50% of the average daytime (12:00–16:00 LT) N2O5 + NO3 signal at our site. However, evidence exists for the presence of elevated daytime N2O5, in addition to the daytime signal at 62 amu. This includes: (1) daytime N2O5 measured via the I(N2O5)− cluster ion with an unheated inlet, which subjects to minimum interferences, and (2) observation of elevated daytime ClNO2 (a product of N2O5 hydrolysis) during a follow-up study. In view of the difficulty in accurately quantifying the contribution from the interferences of PAN and NO2 and un-tested potential interfering chemicals in the real atmosphere, we caution the use of 62 amu in the TD-CIMS for measuring ambient N2O5 in a high NOx environment like Hong Kong. Additional studies are needed to re-examine the daytime issue using other measurement techniques.

scholarly journals Effects of land use on surface–atmosphere exchanges of trace gases and energy in Borneo: comparing fluxes over oil palm plantations and a rainforest

2011 ◽  
Vol 366 (1582) ◽  
pp. 3196-3209 ◽  
Author(s):  
David Fowler ◽  
Eiko Nemitz ◽  
Pawel Misztal ◽  
Chiara Di Marco ◽  
Ute Skiba ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrous Oxide ◽  
Oil Palm ◽  
Trace Gases ◽  
Large Change ◽  
Voc Emissions ◽  
Oil Palm Plantation ◽  
Deposition Velocities ◽  
Volatile Organic ◽  
Effects Of Land Use

This paper reports measurements of land–atmosphere fluxes of sensible and latent heat, momentum, CO 2 , volatile organic compounds (VOCs), NO, NO 2 , N 2 O and O 3 over a 30 m high rainforest canopy and a 12 m high oil palm plantation in the same region of Sabah in Borneo between April and July 2008. The daytime maximum CO 2 flux to the two canopies differs by approximately a factor of 2, 1200 mg C m −2 h −1 for the oil palm and 700 mg C m −2 h −1 for the rainforest, with the oil palm plantation showing a substantially greater quantum efficiency. Total VOC emissions are also larger over the oil palm than over the rainforest by a factor of 3. Emissions of isoprene from the oil palm canopy represented 80 per cent of the VOC emissions and exceeded those over the rainforest in similar light and temperature conditions by on average a factor of 5. Substantial emissions of estragole (1-allyl-4-methoxybenzene) from the oil palm plantation were detected and no trace of this VOC was detected in or above the rainforest. Deposition velocities for O 3 to the rainforest were a factor of 2 larger than over oil palm. Emissions of nitrous oxide were larger from the soils of the oil palm plantation than from the soils of the rainforest by approximately 25 per cent. It is clear from the measurements that the large change in the species composition generated by replacing rainforest with oil palm leads to profound changes in the net exchange of most of the trace gases measured, and thus on the chemical composition of the boundary layer over these surfaces.

scholarly journals Iodine oxide in the global marine boundary layer

2014 ◽  
Vol 14 (15) ◽  
pp. 22217-22243 ◽  
Author(s):  
C. Prados-Roman ◽  
C. A. Cuevas ◽  
T. Hay ◽  
R. P. Fernandez ◽  
A. S. Mahajan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Ozone Depletion ◽  
Marine Boundary Layer ◽  
Geographical Pattern ◽  
Mixing Ratios ◽  
Field Campaigns ◽  
Ozone Depletion Potential ◽  
Ubiquitous Presence ◽  
Inorganic Precursors

Abstract. Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive dataset of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol−1 and, complemented with additional field campaigns, this dataset confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75% to the iodine oxide budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.

scholarly journals Iodine oxide in the global marine boundary layer

2015 ◽  
Vol 15 (2) ◽  
pp. 583-593 ◽  
Author(s):  
C. Prados-Roman ◽  
C. A. Cuevas ◽  
T. Hay ◽  
R. P. Fernandez ◽  
A. S. Mahajan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Ozone Depletion ◽  
Marine Boundary Layer ◽  
Data Set ◽  
Mixing Ratios ◽  
Field Campaigns ◽  
Ozone Depletion Potential ◽  
Ubiquitous Presence ◽  
Inorganic Precursors

Abstract. Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive data set of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol−1 (30% uncertainty) and, complemented with additional field campaigns, this data set confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75 % to the IO budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.

scholarly journals Real-time detection of highly oxidized organosulfates and BSOA marker compounds during the F-BEACh 2014 field study

2017 ◽  
Vol 17 (2) ◽  
pp. 1453-1469 ◽  
Author(s):  
Martin Brüggemann ◽  
Laurent Poulain ◽  
Andreas Held ◽  
Torsten Stelzer ◽  
Christoph Zuth ◽  
...  
Keyword(s):  
Field Study ◽  
Gas Phase ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Mixing Ratios ◽  
Aerosol Mass ◽  
High Solar Radiation ◽  
Marker Compounds ◽  
High Concentrations

Abstract. The chemical composition of ambient organic aerosols was analyzed using complementary mass spectrometric techniques during a field study in central Europe in July 2014 (Fichtelgebirge – Biogenic Emission and Aerosol Chemistry, F-BEACh 2014). Among several common biogenic secondary organic aerosol (BSOA) marker compounds, 93 acidic oxygenated hydrocarbons were detected with elevated abundances and were thus attributed to be characteristic for the organic aerosol mass at the site. Monoterpene measurements exhibited median mixing ratios of 1.6 and 0.8 ppbV for in and above canopy levels respectively. Nonetheless, concentrations for early-generation oxidation products were rather low, e.g., pinic acid (c  =  4.7 (±2.5) ng m−3). In contrast, high concentrations were found for later-generation photooxidation products such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA, c  =  13.8 (±9.0) ng m−3) and 3-carboxyheptanedioic acid (c  =  10.2 (±6.6) ng m−3), suggesting that aged aerosol masses were present during the campaign period. In agreement, HYSPLIT trajectory calculations indicate that most of the arriving air masses traveled long distances (>  1500 km) over land with high solar radiation. In addition, around 47 % of the detected compounds from filter sample analysis contained sulfur, confirming a rather high anthropogenic impact on biogenic emissions and their oxidation processes. Among the sulfur-containing compounds, several organosulfates, nitrooxy organosulfates, and highly oxidized organosulfates (HOOS) were tentatively identified by high-resolution mass spectrometry. Correlations among HOOS, sulfate, and highly oxidized multifunctional organic compounds (HOMs) support the hypothesis of previous studies that HOOS are formed by reactions of gas-phase HOMs with particulate sulfate. Moreover, periods with high relative humidity indicate that aqueous-phase chemistry might play a major role in HOOS production. However, for dryer periods, coinciding signals for HOOS and gas-phase peroxyradicals (RO2&amp;bullet;) were observed, suggesting RO2&amp;bullet; to be involved in HOOS formation.

scholarly journals Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign

2008 ◽  
Vol 8 (20) ◽  
pp. 6223-6243 ◽  
Author(s):  
L. Ganzeveld ◽  
G. Eerdekens ◽  
G. Feig ◽  
H. Fischer ◽  
H. Harder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Residual Layer ◽  
Oxidation Products ◽  
Emission Flux ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products.

Sign in / Sign up

Export Citation Format

Share Document