Meteorological and fire impacts on tropospheric ozone concentration over tropical forest in the Congo Basin

2021 ◽  
Author(s):  
Inês Vieira ◽  
Hans Verbeeck ◽  
Félicien Meunier ◽  
Marc Peaucelle ◽  
Lodewijk Lefevre ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Ozone Concentration ◽  
Primary Productivity ◽  
Tropospheric Ozone ◽  
Congo Basin ◽  
Solar Irradiation ◽  
Ozone Concentrations ◽  
Ozone Precursor ◽  
The Impact ◽  
Ozone Levels

<p>Tropospheric ozone is a greenhouse gas, and high tropospheric ozone levels can directly impact plant growth and human health. In the Congo basin, simulations predict high ozone concentrations, induced by high ozone precursor (VOC and NOx) concentrations and high solar irradiation, which trigger the chemical reactions that form ozone. Additionally, biomass burning activities are widespread on the African continent, playing a crucial role in ozone precursor production. How these potentially high ozone levels impact tropical forest primary productivity remains poorly understood, and field-based ozone monitoring is completely lacking from the Congo basin. This study intends to show preliminary results from the first full year of in situ measurements of ozone concentration in the Congo Basin (i.e., Yangambi, Democratic Republic of the Congo). We show the relationships between meteorological variables (temperature, precipitation, radiation, wind direction and speed), fire occurrence (derived from remote sensing products) and ozone concentrations at a new continuous monitoring station in the heart of the Congo Basin. First results show higher daily mean ozone levels (e.g. 43 ppb registered in January 2020) during dry season months (December-February). We identify a strong diurnal cycle, where minimum values of ozone (almost near zero) are registered during night hours, and maximum values (near 100 ppb) are registered during the daytime. We also verify that around 2.5% of the ozone measurements exceeds a toxicity level (potential for ozone to damage vegetation) of 40 ppb. In the longer term, these measurements should improve the accuracy of future model simulations in the Congo Basin and will be used to assess the impact of ozone on the tropical forest’s primary productivity.</p>

scholarly journals Forecast of Hourly Tropospheric Ozone Concentration in Quang Ninh using MLP and SVM

2020 ◽  
Vol 36 (3) ◽  
Author(s):  
Nguyen Thi Thu Phuong ◽  
Mac Duy Hung ◽  
Duong Thanh Nam ◽  
Nghiem Trung Dung
Keyword(s):  
Ozone Concentration ◽  
Atmospheric Pressure ◽  
Tropospheric Ozone ◽  
Meteorological Parameters ◽  
Correlation Coefficients ◽  
High Standard ◽  
Support Vector ◽  
Observation Data ◽  
Quang Ninh ◽  
Ozone Levels

Support vector machine (SVM) and multilayer perceptron (MLP) were used to forecast hourly tropospheric ozone concentration at three locations of Quang Ninh, namely Cao Xanh, Uong Bi and Phuong Nam. Data used to train the models are the hourly concentrations of gaseous pollutants (O3, NO, NO2, CO) and meteorological parameters including wind direction, wind speed, temperature, atmospheric pressure, relative humidity measured in the 2016. Both models accurately forecast tropospheric ozone levels compared to the observation data. The correlation coefficients (r) of the models applied for the three locations range from 0.85 to 0.91. In addition, SVM exhibits a more accurate prediction than MLP, especially for those with large variations, i.e. high standard deviations.

Variation of the surface ozone concentration during precipitation

2020 ◽  
Author(s):  
Igor V. Ptashnik ◽  
Boris D. Belan ◽  
Denis E. Savkin ◽  
Gennadii N. Tolmachev ◽  
Tatayana K. Sklyadneva ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Ozone Concentration ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Chem Phys ◽  
Global Scale ◽  
Washington Dc ◽  
American Geophysical ◽  
The Impact ◽  
Surface Ozone Concentration

<p>In the review compiled by Monks et al. (2015), it is noted that the main variations in the tropospheric ozone are determined by the exchange between the troposphere and the stratosphere, in-situ photochemical production from gaseous precursors depending on their composition and concentration, solar radiation income, and meteorological conditions. The impact of precipitation on the surface ozone concentration is a less well-studied factor.</p><p>The process of ozone interaction with precipitation was studied theoretically (Heicklen, 1982). Two ways of the above process were analyzed: adsorption of gas molecules on the surface of a particle and a chemical reaction with its surface. There are no direct data on the verification of these findings in the literature. At the same time, there is some evidence of a possible link between precipitation and ozone.</p><p>This study is aimed to analyze the presence or absence of changes in the ozone concentration during precipitation. Variations of the surface ozone concentration (SOC) in the presence of precipitation were analyzed using the long-term data obtained at the TOR-station established in 1992 for ozone monitoring in Tomsk. It was revealed that these changes can be both positive (increase in concentration) and negative. The sharp changes in the SOC are observed when frontal precipitation takes place. In the presence of air-mass precipitation, the sign and magnitude of the change is determined by the diurnal variation of ozone concentration.</p><p>The analysis showed a coincidence of the SOC growth during precipitation with its increase in diurnal variation in 59% of cases. The coincidence in the wave of the concentration decline in the diurnal variation with decreasing precipitation rate is even higher and amounts to 85%.</p><p>Airborne sounding carried out in the vicinity of the TOR-station shown that in a number of cases the ozone deposition from the boundary layer is observed upon the transition of thermal stratification during the precipitation to neutral.</p><p> </p><p>Monks P. S, Archibald A. T., Colette A., Cooper O., Coyle M., Derwent R., Fowler D., Granier C., Law K. S., Mills G. E., Stevenson D. S., Tarasova O., Thouret V., von Schneidemesser E., Sommariva R., Wild O., Williams M. L. Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer. Atmos. Chem. Phys., 2015, v.15, N15, p.8889–8973.</p><p>Heicklen J. The Removal of Atmospheric Gases by Particulate Matter. In Heterogeneous Atmospheric Chemistry, ed. D. R. Schryer, Geophysical Monograph 26. American Geophysical Union, Washington, DC, USA, 1982, p. 93-98.</p>

scholarly journals Megacity ozone air quality under four alternative future scenarios

2012 ◽  
Vol 12 (10) ◽  
pp. 4413-4428 ◽  
Author(s):  
T. M. Butler ◽  
Z. S. Stock ◽  
M. R. Russo ◽  
H. A. C. Denier van der Gon ◽  
M. G. Lawrence
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Future Scenarios ◽  
Mixing Ratios ◽  
Background Ozone ◽  
Alternative Future ◽  
Modelling Studies ◽  
Emissions Scenarios ◽  
Ozone Precursor ◽  
The Impact

Abstract. The impact of the megacities of the world on global tropospheric ozone, and conversely, the extent to which megacities are influenced by emissions of ozone precursors from outside of the megacities is examined under the four alternative RCP ("Representative Concentration Pathway") emissions scenarios. Despite accounting for about 6% of present-day anthropogenic emissions of ozone precursor species, the contribution of emissions from megacities to global tropospheric ozone is calculated to be 0.84%. By 2100 this contribution falls to between 0.18% and 0.62% depending on the scenario, with the lower value being for the most-polluting of the four future emissions scenarios due to stringent controls on ozone precursor emissions from highly populated areas combined with a stronger tropospheric background ozone field. The higher end of this range is from the least-polluting of the four emissions scenarios, due to lower background tropospheric ozone combined with the use of a simpler downscaling methodology in the construction of the scenario, which results in higher emissions from megacities. Although the absolute impact of megacities on global ozone is small, an important result of this study is that under all future scenarios, future air quality in megacities is expected to be less influenced by local emissions within the cities, but instead more influenced by emission sources outside of the cities, with mixing ratios of background ozone projected to play an increasing role in megacity air quality throughout the 21st century. Assumptions made when downscaling the emissions scenarios onto the grids used in such modelling studies can have a large influence on these results; future generations of emissions scenarios should include spatially explicit representations or urban development suitable for air quality studies using global chemical transport models.

scholarly journals Historical Aerial Surveys Map Long-Term Changes of Forest Cover and Structure in the Central Congo Basin

2020 ◽  
Vol 12 (4) ◽  
pp. 638 ◽  
Author(s):  
Koen Hufkens ◽  
Thalès de Haulleville ◽  
Elizabeth Kearsley ◽  
Kim Jacobsen ◽  
Hans Beeckman ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Forest Cover ◽  
Congo Basin ◽  
Spatial And Temporal Patterns ◽  
Smallholder Farming ◽  
Aboveground Carbon ◽  
Decadal Scale ◽  
Long Term Changes ◽  
The Impact

Given the impact of tropical forest disturbances on atmospheric carbon emissions, biodiversity, and ecosystem productivity, accurate long-term reporting of Land-Use and Land-Cover (LULC) change in the pre-satellite era (<1972) is an imperative. Here, we used a combination of historical (1958) aerial photography and contemporary remote sensing data to map long-term changes in the extent and structure of the tropical forest surrounding Yangambi (DR Congo) in the central Congo Basin. Our study leveraged structure-from-motion and a convolutional neural network-based LULC classifier, using synthetic landscape-based image augmentation to map historical forest cover across a large orthomosaic (~93,431 ha) geo-referenced to ~4.7 ± 4.3 m at submeter resolution. A comparison with contemporary LULC data showed a shift from previously highly regular industrial deforestation of large areas to discrete smallholder farming clearing, increasing landscape fragmentation and providing opportunties for substantial forest regrowth. We estimated aboveground carbon gains through reforestation to range from 811 to 1592 Gg C, partially offsetting historical deforestation (2416 Gg C), in our study area. Efforts to quantify long-term canopy texture changes and their link to aboveground carbon had limited to no success. Our analysis provides methods and insights into key spatial and temporal patterns of deforestation and reforestation at a multi-decadal scale, providing a historical context for past and ongoing forest research in the area.

scholarly journals European summer surface ozone 1990–2100

2012 ◽  
Vol 12 (3) ◽  
pp. 7705-7726 ◽  
Author(s):  
J. Langner ◽  
M. Engardt ◽  
C. Andersson
Keyword(s):  
Climate Change ◽  
Decadal Variability ◽  
Surface Ozone ◽  
Regional Climate ◽  
Climate Change Impacts ◽  
Regional Climate Change ◽  
Ozone Concentrations ◽  
Ozone Precursor ◽  
The Impact ◽  
Surface O3

Abstract. The impact of climate change and changes in ozone precursor emissions on summer surface ozone in Europe were studied using a regional CTM over the period 1990 to 2100. Two different climate simulations under the SRES A1B scenario together with ozone precursor emission changes from the RCP4.5 scenario were used as model input. In southern Europe regional climate change leads to increasing surface ozone concentrations during April–September, but projected emission reductions in Europe have a stronger effect, resulting in net reductions of surface ozone concentrations. In northern Europe regional climate change decreases surface O3 and reduced emissions acts to further strengthen this trend also when including increasing hemispheric background concentrations, although on the British Isles the combined effect is an increase. Due to substantial decadal variability in the simulations it is important to study averages over sufficiently long time periods in order to be able to extract robust signals of climate change impacts on surface O3 concentrations.

scholarly journals Tropospheric ozone assessment report: Global ozone metrics for climate change, human health, and crop/ecosystem research

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Allen S. Lefohn ◽  
Christopher S. Malley ◽  
Luther Smith ◽  
Benjamin Wells ◽  
Milan Hazucha ◽  
...  
Keyword(s):  
Temporal Variation ◽  
Human Health ◽  
Tropospheric Ozone ◽  
Temporal Trends ◽  
Spatial And Temporal Variation ◽  
Site Location ◽  
Ecosystem Research ◽  
Assessment Report ◽  
Ozone Concentrations ◽  
Ozone Levels

Assessment of spatial and temporal variation in the impacts of ozone on human health, vegetation, and climate requires appropriate metrics. A key component of the Tropospheric Ozone Assessment Report (TOAR) is the consistent calculation of these metrics at thousands of monitoring sites globally. Investigating temporal trends in these metrics required that the same statistical methods be applied across these ozone monitoring sites. The nonparametric Mann-Kendall test (for significant trends) and the Theil-Sen estimator (for estimating the magnitude of trend) were selected to provide robust methods across all sites. This paper provides the scientific underpinnings necessary to better understand the implications of and rationale for selecting a specific TOAR metric for assessing spatial and temporal variation in ozone for a particular impact. The rationale and underlying research evidence that influence the derivation of specific metrics are given. The form of 25 metrics (4 for model-measurement comparison, 5 for characterization of ozone in the free troposphere, 11 for human health impacts, and 5 for vegetation impacts) are described. Finally, this study categorizes health and vegetation exposure metrics based on the extent to which they are determined only by the highest hourly ozone levels, or by a wider range of values. The magnitude of the metrics is influenced by both the distribution of hourly average ozone concentrations at a site location, and the extent to which a particular metric is determined by relatively low, moderate, and high hourly ozone levels. Hence, for the same ozone time series, changes in the distribution of ozone concentrations can result in different changes in the magnitude and direction of trends for different metrics. Thus, dissimilar conclusions about the effect of changes in the drivers of ozone variability (e.g., precursor emissions) on health and vegetation exposure can result from the selection of different metrics.

scholarly journals Inter-comparison and assessment of gridded climate products over tropical forests during the 2015/2016 El Niño

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170406 ◽  
Author(s):  
C. Burton ◽  
S. Rifai ◽  
Y. Malhi
Keyword(s):  
Southeast Asia ◽  
Tropical Forest ◽  
Tropical Forests ◽  
Air Temperature ◽  
El Niño ◽  
El Nino ◽  
Congo Basin ◽  
Wide Range ◽  
Spatio Temporal ◽  
The Impact

To understand the impacts of extreme climate events, it is first necessary to understand the spatio-temporal characteristics of the event. Gridded climate products are frequently used to describe climate patterns but have been shown to perform poorly over data-sparse regions such as tropical forests. Often, they are uncritically employed in a wide range of studies linking tropical forest processes to large-scale climate variability. Here, we conduct an inter-comparison and assessment of near-surface air temperature fields supplied by four state-of-the-art reanalysis products, along with precipitation estimates supplied by four merged satellite-gauge rainfall products. Firstly, spatio-temporal patterns of temperature and precipitation anomalies during the 2015–2016 El Niño are shown for each product to characterize the impact of the El Niño on the tropical forest biomes of Equatorial Africa, Southeast Asia and South America. Using meteorological station data, a two-stage assessment is then conducted to determine which products most reliably model tropical climates during the 2015–2016 El Niño, and which perform best over the longer-term satellite observation period (1980–2016). Results suggest that eastern Amazonia, parts of the Congo Basin and mainland Southeast Asia all experienced significant monthly mean temperature anomalies during the El Niño, while northeastern Amazonia, eastern Borneo and southern New Guinea experienced significant precipitation deficits. Our results suggest ERA-Interim and MERRA2 are the most reliable air temperature datasets, while TRMM 3B42 V7 and CHIRPS v2.0 are the best-performing rainfall datasets. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals On the impact of temperature on tropospheric ozone concentration levels in urban environments

2008 ◽  
Vol 117 (3) ◽  
pp. 227-236 ◽  
Author(s):  
E. Stathopoulou ◽  
G. Mihalakakou ◽  
M. Santamouris ◽  
H. S. Bagiorgas
Keyword(s):  
Ozone Concentration ◽  
Tropospheric Ozone ◽  
Urban Environments ◽  
The Impact ◽  
Concentration Levels

scholarly journals Principal Component Analysis of Chlorophyll Content in Tobacco, Bean and Petunia Plants Exposed to Different Tropospheric Ozone Concentrations

2014 ◽  
Vol 12 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Klaudia Borowiak ◽  
Janina Zbierska ◽  
Anna Budka ◽  
Dariusz Kayzer
Keyword(s):  
Principal Component Analysis ◽  
Chlorophyll Content ◽  
Plant Species ◽  
Ozone Concentration ◽  
Tropospheric Ozone ◽  
Principal Component ◽  
Ambient Air ◽  
Component Analysis ◽  
Chlorophyll Contents ◽  
Ozone Concentrations

Abstract Three plant species were assessed in this study - ozone-sensitive and -resistant tobacco, ozone-sensitive petunia and bean. Plants were exposed to ambient air conditions for several weeks in two sites differing in tropospheric ozone concentrations in the growing season of 2009. Every week chlorophyll contents were analysed. Cumulative ozone effects on the chlorophyll content in relation to other meteorological parameters were evaluated using principal component analysis, while the relation between certain days of measurements of the plants were analysed using multivariate analysis of variance. Results revealed variability between plant species response. However, some similarities were noted. Positive relations of all chlorophyll forms to cumulative ozone concentration (AOT 40) were found for all the plant species that were examined. The chlorophyll b/a ratio revealed an opposite position to ozone concentration only in the ozone-resistant tobacco cultivar. In all the plant species the highest average chlorophyll content was noted after the 7th day of the experiment. Afterwards, the plants usually revealed various responses. Ozone-sensitive tobacco revealed decrease of chlorophyll content, and after few weeks of decline again an increase was observed. Probably, due to the accommodation for the stress factor. While during first three weeks relatively high levels of chlorophyll contents were noted in ozone-resistant tobacco. Petunia revealed a slow decrease of chlorophyll content and the lowest values at the end of the experiment. A comparison between the plant species revealed the highest level of chlorophyll contents in ozone-resistant tobacco.

Evidence of a 50-year increase in tropospheric ozone in Upper Bavaria

1994 ◽  
Vol 12 (12) ◽  
pp. 1197-1206 ◽  
Author(s):  
M. Schmidt
Keyword(s):  
Ozone Concentration ◽  
Tropospheric Ozone ◽  
Mixing Ratios ◽  
The Past ◽  
Ozone Concentrations ◽  
Bavarian Alps ◽  
Non Linear ◽  
Northern Edge ◽  
Wet Chemical ◽  
Linear Trends

Abstract. In a series of ozone-sonde soundings at the Hohenpeißenberg observatory, starting in 1967, the most striking features are increases of \\sim2.2% per year in all tropospheric heights up to 8 km during the past 24 years. These facts have recently been published and discussed by several authors. In this paper, we present some evidence for the increase of tropospheric ozone concentrations during the past 50 years 1940-1990 in the territory of the northern edge of the Bavarian Alps, including the Hohenpeißenberg data. In December 1940 and August 1942, probably the first exact wet-chemical vertical soundings of ozone up to 9 km height were made by an aircraft in the region mentioned. These results were published in the earlier literature. We have converted the results of the flights on 4 days in December 1940 and on 6 days in August 1942 to modern units and have compared them with the Hohenpeißenberg ozone-sonde data of the December and August months. We also compared the data at the ground with the August results of Paris-Montsouris 1886-1898. Our results show an increase of ozone concentration at all tropospheric heights in Upper Bavaria during the past 50 years, compared with the Montsouris data in August during the past 105 years. In the recently published papers, the increases since 1967 were approximated linearly.Our results, extended to the past, show non-linear trends, with steeper increases since 1975-1979. Possible reasons for these findings are discussed. Quite recently (in case of the December months since 1986/87, the August months since 1990), the ozone mixing ratios at and above Hohenpeißenberg seem to have decreased.

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