scholarly journals Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia

2016 ◽  
Author(s):  
Suzane S. de Sá ◽  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Matthew K. Newburn ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Atmospheric Chemistry ◽  
Regional Climate ◽  
Urban Pollution ◽  
Factor Loading ◽  
Sulfate Concentration ◽  
Wet Season ◽  
Data Set ◽  
Aerosol Mass ◽  
Central Amazonia

Abstract. The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 hours downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Mass spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor (“IEPOX-SOA factor”) was associated with PM production by the IEPOX pathway. Loadings of this factor correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C5-alkene triols and 2-methyltetrols (R = 0.96 and 0.78, respectively). Factor loading, as well as the ratio of the factor loading to organic PM mass concentration, decreased under polluted compared to background conditions. For the study period, sulfate concentration explained 37 % of the variability in the factor loading. After segregation of the data set by NOy concentration, the sulfate concentration explained up to 75 % of the variability in factor loading within the NOy subsets. The sulfate-detrended IEPOX-SOA factor loading decreased by two- to three-fold for an increase in NOy concentration from 0.5 to 2 ppb. The suppressing effects of elevated NO dominated over the enhancing effects of higher sulfate with respect to the production of IEPOX-derived PM. Relative to background conditions, the Manaus pollution contributed more significantly to NOy than to sulfate. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.

scholarly journals Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia

2017 ◽  
Vol 17 (11) ◽  
pp. 6611-6629 ◽  
Author(s):  
Suzane S. de Sá ◽  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Matthew K. Newburn ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Atmospheric Chemistry ◽  
Regional Climate ◽  
Urban Pollution ◽  
Factor Loading ◽  
Data Sets ◽  
Sulfate Concentration ◽  
Wet Season ◽  
Aerosol Mass ◽  
Central Amazonia

Abstract. The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 h downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Mass spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor (IEPOX-SOA factor) was associated with PM production by the IEPOX pathway. The IEPOX-SOA factor loadings correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C5-alkene triols and 2-methyltetrols (R = 0. 96 and 0.78, respectively). The factor loading, as well as the ratio f of the loading to organic PM mass concentration, decreased under polluted compared to background conditions. For an increase in NOy concentration from 0.5 to 2 ppb, the factor loading and f decreased by two to three fold. Overall, sulfate concentration explained 37 % of the variability in the factor loading. After segregation of factor loading into subsets based on NOy concentration, the sulfate concentration explained up to 75 % of the variability. Considering both factors, the data sets show that the suppressing effects of increased NO concentrations dominated over the enhancing effects of higher sulfate concentrations. The pollution from Manaus elevated NOy concentrations more significantly than sulfate concentrations relative to background conditions. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.

scholarly journals New insights into PM<sub>2.5</sub> chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry

2016 ◽  
Vol 16 (5) ◽  
pp. 3207-3225 ◽  
Author(s):  
Miriam Elser ◽  
Ru-Jin Huang ◽  
Robert Wolf ◽  
Jay G. Slowik ◽  
Qiyuan Wang ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Solution Space ◽  
Primary Sources ◽  
Aerodynamic Diameter ◽  
Data Set ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Aerosol Mass Spectrometry ◽  
Polycyclic Aromatic ◽  
On Line

Abstract. During winter 2013–2014 aerosol mass spectrometer (AMS) measurements were conducted for the first time with a novel PM2.5 (particulate matter with aerodynamic diameter  ≤ 2.5 µm) lens in two major cities of China: Xi'an and Beijing. We denote the periods with visibility below 2 km as extreme haze and refer to the rest as reference periods. During the measurements in Xi'an an extreme haze covered the city for about a week and the total non-refractory (NR)-PM2.5 mass fraction reached peak concentrations of over 1000 µg m−3. During the measurements in Beijing two extreme haze events occurred, but the temporal extent and the total concentrations reached during these events were lower than in Xi'an. Average PM2.5 concentrations of 537 ± 146 and 243 ± 47 µg m−3 (including NR species and equivalent black carbon, eBC) were recorded during the extreme haze events in Xi'an and Beijing, respectively. During the reference periods the measured average concentrations were 140 ± 99 µg m−3 in Xi'an and 75 ± 61 µg m−3 in Beijing. The relative composition of the NR-PM2.5 evolved substantially during the extreme haze periods, with increased contributions of the inorganic components (mostly sulfate and nitrate). Our results suggest that the high relative humidity present during the extreme haze events had a strong effect on the increase of sulfate mass (via aqueous phase oxidation of sulfur dioxide). Another relevant characteristic of the extreme haze is the size of the measured particles. During the extreme haze events, the AMS showed much larger particles, with a volume weighted mode at about 800 to 1000 nm, in contrast to about 400 nm during reference periods. These large particle sizes made the use of the PM2.5 inlet crucial, especially during the severe haze events, where 39 ± 5 % of the mass would have been lost in the conventional PM1 (particulate matter with aerodynamic diameter ≤ 1 µm) inlet. A novel positive matrix factorization procedure was developed to apportion the sources of organic aerosols (OA) based on their mass spectra using the multilinear engine (ME-2) controlled via the source finder (SoFi). The procedure allows for an effective exploration of the solution space, a more objective selection of the best solution and an estimation of the rotational uncertainties. Our results clearly show an increase of the oxygenated organic aerosol (OOA) mass during extreme haze events. The contribution of OOA to the total OA increased from the reference to the extreme haze periods from 16.2 ± 1.1 to 31.3 ± 1.5 % in Xi'an and from 15.7 ± 0.7 to 25.0 ± 1.2 % in Beijing. By contrast, during the reference periods the total OA mass was dominated by domestic emissions of primary aerosols from biomass burning in Xi'an (42.2 ± 1.5 % of OA) and coal combustion in Beijing (55.2 ± 1.6 % of OA). These two sources are also mostly responsible for extremely high polycyclic aromatic hydrocarbon (PAH) concentrations measured with the AMS (campaign average of 2.1 ± 2.0 µg m−3 and frequent peak concentrations above 10 µg m−3). To the best of our knowledge, this is the first data set where the simultaneous extraction of these two primary sources could be achieved in China by conducting on-line AMS measurements at two areas with contrasted emission patterns.

scholarly journals Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

2019 ◽  
Vol 19 (12) ◽  
pp. 7973-8001 ◽  
Author(s):  
Suzane S. de Sá ◽  
Luciana V. Rizzo ◽  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Anthropogenic Impacts ◽  
Dry Season ◽  
Primary Study ◽  
Wet Season ◽  
Factor Loadings ◽  
Central Amazonia ◽  
Mass Concentrations

Abstract. Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of PM1 concentration, composition, and optical properties in central Amazonia during the dry season, focusing on the anthropogenic impacts. The primary study site was located 70 km downwind of Manaus, a city of over 2 million people in Brazil, as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM1 composition, and aethalometer measurements were used to derive the absorption coefficient babs,BrC of brown carbon (BrC) at 370 nm. Non-refractory PM1 mass concentrations averaged 12.2 µg m−3 at the primary study site, dominated by organics (83 %), followed by sulfate (11 %). A decrease in babs,BrC was observed as the mass concentration of nitrogen-containing organic compounds decreased and the organic PM1 O:C ratio increased, suggesting atmospheric bleaching of the BrC components. The organic PM1 was separated into six different classes by positive-matrix factorization (PMF), and the mass absorption efficiency Eabs associated with each factor was estimated through multivariate linear regression of babs,BrC on the factor loadings. The largest Eabs values were associated with urban (2.04±0.14 m2 g−1) and biomass-burning (0.82±0.04 to 1.50±0.07 m2 g−1) sources. Together, these sources contributed at least 80 % of babs,BrC while accounting for 30 % to 40 % of the organic PM1 mass concentration. In addition, a comparison of organic PM1 composition between wet and dry seasons revealed that only part of the 9-fold increase in mass concentration between the seasons can be attributed to biomass burning. Biomass-burning factor loadings increased by 30-fold, elevating its relative contribution to organic PM1 from about 10 % in the wet season to 30 % in the dry season. However, most of the PM1 mass (>60 %) in both seasons was accounted for by biogenic secondary organic sources, which in turn showed an 8-fold seasonal increase in factor loadings. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Furthermore, fuzzy c-means clustering identified three clusters, namely “baseline”, “event”, and “urban” to represent different pollution influences during the dry season. The baseline cluster, representing the dry season background, was associated with a mean mass concentration of 9±3 µg m−3. This concentration increased on average by 3 µg m−3 for both the urban and the event clusters. The event cluster, representing an increased influence of biomass burning and long-range transport of African volcanic emissions, was characterized by remarkably high sulfate concentrations. The urban cluster, representing the influence of Manaus emissions on top of the baseline, was characterized by an organic PM1 composition that differed from the other two clusters. The differences discussed suggest a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season.

scholarly journals Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

2019 ◽  
Author(s):  
Suzane S. de Sá ◽  
Luciana V. Rizzo ◽  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Fold Increase ◽  
Dry Season ◽  
Atmospheric Particulate Matter ◽  
Primary Study ◽  
Wet Season ◽  
Central Amazonia ◽  
Urban Emissions

Abstract. Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of submicron PM1 concentration, composition, and optical properties in central Amazonia during the dry season. The focus is on delineating the anthropogenic impact on the observed quantities, especially as related to the organic PM1. The primary study site was located 70 km to the west of Manaus, a city of over two million people in Brazil. As part of the GoAmazon2014/5 experiment, datasets from a large suite of instrumentation were employed. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM1 composition, and aethalometer measurements were used to derive the absorption coefficient babs,BrC of brown carbon (BrC) at 370 nm. The relationships of babs,BrC with AMS-measured quantities showed that the absorption was associated with less-oxidized, nitrogen-containing organic compounds. Atmospheric processing appeared to bleach the BrC components. The organic PM1 was separated into different classes by positive-matrix factorization (PMF). Estimates of the effective mass absorption efficiency associated with each PMF factor were obtained. Biomass burning and urban emissions appeared to contribute at least 80 % of babs,BrC while accounting for 30 to 40 % of the organic PM1 mass concentration. In addition, a comparison of organic PM1 composition between wet and dry seasons revealed that only a fraction of the nine-fold increase in mass concentration between the seasons was due to biomass burning. An eight-fold increase in biogenic secondary organic PM1 was observed. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Fuzzy c-means clustering identified three clusters to represent different pollution influences during the dry season, including baseline (dry season background, which includes biomass burning), event (increased influence of biomass burning and long-range transport of African volcanic emissions), and urban (Manaus influence on top of the background). The baseline cluster was associated with a mean mass concentration of 9 ± 3 μg m−3. This concentration increased on average by 3 μg m−3 for both the urban and the event clusters. The event cluster was characterized by remarkably high sulfate concentrations. Differences in the organic PM1 composition for the urban cluster compared to the other two clusters suggested a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season. 

scholarly journals Aerosol and precipitation chemistry in a remote site in Central Amazonia: the role of biogenic contribution

2007 ◽  
Vol 7 (4) ◽  
pp. 11465-11509 ◽  
Author(s):  
T. Pauliquevis ◽  
L. L. Lara ◽  
M. L. Antunes ◽  
P. Artaxo
Keyword(s):  
Biomass Burning ◽  
Precipitation Chemistry ◽  
Remote Site ◽  
Wet Season ◽  
Rainwater Chemistry ◽  
Deposition Rates ◽  
Aerosol Mass ◽  
Central Amazonia ◽  
Fine Mode ◽  
Particulate Mass

Abstract. A long-term (2–3 years) measurement of aerosol and precipitation chemistry was carried out in a remote site in Central Amazonia, Balbina, (1°55' S, 59°29' W, 174 m above sea level), about 200 km north of Manaus city. Aerosols were sampled using stacked filter units (SFU), which separate fine (d<2.5 μm) and coarse mode (2.5 μm<d<10.0 μm). Filters were analyzed for particulate mass (PM), black carbon (BC) and elemental composition by Particle Induced X-Ray Emission (PIXE). Rainwater samples were collected using a wet-only sampler and samples were analyzed for pH and ionic composition, which was determined using ionic chromatography (IC). Aerosol mass was predominantly of biogenic origin and concentrated in coarse mode, comprising up to 81% of PM10 concentration during the wet season. Natural biogenic aerosol also dominates the fine mode in the wet season, with very low concentrations (average 2.2 μg/m3). Large-scale transport of smoke from biomass burning was the second most important contribution, reaching 77% of fine mode particulate mass during the dry season. Soil dust was responsible by a minor fraction of the aerosol mass (less than 17%). Rainwater chemistry was controlled by biogenic emissions. The volume-weighted mean (VWM) pH was 4.90. The most important contribution to acidity was weak organic acids. The organic acidity was predominantly associated with the presence of acetic acid, instead of formic acid which is more often observed in pristine tropical areas. Deposition rates for major species did not differ significantly between dry and wet season, except for NH4+ and acetate, which had smaller deposition rates during dry season. While biomass burning emissions were clearly identified in the aerosol component, it was not possible to discern any presence of biomass burning emissions in rainwater chemistry. The long-range transport of sea salt and biogenic particles was observed both in aerosols and rainwater composition. The results showed here indicate that in Amazonia it is still possible to observe pristine atmospheric conditions, relatively free of anthropogenic influences.

scholarly journals Meteorological Characteristics Associated with Air Pollution in Bucharest Greater Area, Romania

2020 ◽  
Vol 4 (1) ◽  
pp. 22
Author(s):  
Tiberiu Hriscan ◽  
Silviu Chirita ◽  
Mihaela Burcea ◽  
Andreea Calcan ◽  
Marius Corbu ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Meteorological Parameters ◽  
Gaseous Species ◽  
Data Set ◽  
Air Mass ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Precipitation Characteristics ◽  
Deposition Processes

This study examines how the mass concentrations of gaseous species (NO, NO2, NOx, O3, SO2, CO, C6H6) and particulate matter PM10, PM2.5 (particulate matter less than 10 µm and less than 2.5 μm) might be linked with precipitation characteristics using an observational data set for five years (2015–2019) in the Bucharest metropolitan area. Particulate matter data and meteorological parameters at each site (atmospheric pressure, relative humidity, temperature, solar radiation, wind speed and direction) were extracted from the publicly available Romanian National Air Quality Database. Meteorology was complemented with radar products (images, reflectivity, echotops) from the C-band meteorological radar of the National Meteorological Administration in Bucharest. Change in aerosol mass concentration during the evolution of the precipitation events was investigated. The aerosol scavenging coefficients were estimated and compared with those in the scientific literature. Correlations between meteorological parameters and ambient pollutant levels were analyzed. The connection between meteorological phenomena occurrence and air mass origin was investigated by computing air mass backward trajectories for a 72-h period using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Results demonstrate the good capability of the convective precipitating systems to clear the atmosphere of fine aerosol and gaseous pollutant species. The obtained results are important for the modeling of air quality and for investigations of aerosol wet deposition processes.

scholarly journals Aerosol and precipitation chemistry measurements in a remote site in Central Amazonia: the role of biogenic contribution

2012 ◽  
Vol 12 (11) ◽  
pp. 4987-5015 ◽  
Author(s):  
T. Pauliquevis ◽  
L. L. Lara ◽  
M. L. Antunes ◽  
P. Artaxo
Keyword(s):  
Biomass Burning ◽  
Precipitation Chemistry ◽  
Dry Season ◽  
Sea Salt ◽  
Remote Site ◽  
Wet Season ◽  
Deposition Rates ◽  
Aerosol Mass ◽  
Coarse Mode ◽  
Central Amazonia

Abstract. In this analysis a 3.5 years data set of aerosol and precipitation chemistry, obtained in a remote site in Central Amazonia (Balbina, (1°55' S, 59°29' W, 174 m a.s.l.), about 200 km north of Manaus) is discussed. Aerosols were sampled using stacked filter units (SFU), which separate fine (d < 2.5 μm) and coarse mode (2.5 μm < d < 10.0 μm) aerosol particles. Filters were analyzed for particulate mass (PM), Equivalent Black Carbon (BCE) and elemental composition by Particle Induced X-Ray Emission (PIXE). Rainwater samples were collected using a wet-only sampler and samples were analyzed for pH and ionic composition, which was determined using ionic chromatography (IC). Natural sources dominated the aerosol mass during the wet season, when it was predominantly of natural biogenic origin mostly in the coarse mode, which comprised up to 81% of PM10. Biogenic aerosol from both primary emissions and secondary organic aerosol dominates the fine mode in the wet season, with very low concentrations (average 2.2 μg m-3). Soil dust was responsible for a minor fraction of the aerosol mass (less than 17%). Sudden increases in the concentration of elements as Al, Ti and Fe were also observed, both in fine and coarse mode (mostly during the April-may months), which we attribute to episodes of Saharan dust transport. During the dry periods, a significant contribution to the fine aerosols loading was observed, due to the large-scale transport of smoke from biomass burning in other portions of the Amazon basin. This contribution is associated with the enhancement of the concentration of S, K, Zn and BCE. Chlorine, which is commonly associated to sea salt and also to biomass burning emissions, presented higher concentration not only during the dry season but also for the April–June months, due to the establishment of more favorable meteorological conditions to the transport of Atlantic air masses to Central Amazonia. The chemical composition of rainwater was similar to those ones observed in other remote sites in tropical forests. The volume-weighted mean (VWM) pH was 4.90. The most important contribution to acidity was from weak organic acids. The organic acidity was predominantly associated with the presence of acetic acid instead of formic acid, which is more often observed in pristine tropical areas. Wet deposition rates for major species did not differ significantly between dry and wet season, except for NH4+, citrate and acetate, which had smaller deposition rates during dry season. While biomass burning emissions were clearly identified in the aerosol component, it did not present a clear signature in rainwater. The biogenic component and the long-range transport of sea salt were observed both in aerosols and rainwater composition. The results shown here indicate that in Central Amazonia it is still possible to observe quite pristine atmospheric conditions, relatively free of anthropogenic influences.

Atmospheric impact of sesquiterpenes in the Amazon rainforest

2020 ◽  
Author(s):  
Nora Zannoni ◽  
Stefan Wolff ◽  
Anywhere Tsokankunku ◽  
Matthias Soergel ◽  
Marta Sa ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Forest Canopy ◽  
Dry Season ◽  
Amazon Rainforest ◽  
Wet Season ◽  
Organic Species ◽  
Central Amazonia ◽  
Volatile Organic ◽  
Chromatographic Peaks ◽  
Ozone Reactivity

&lt;p&gt;Sesquiterpenes (C&lt;sub&gt;15&lt;/sub&gt;H&lt;sub&gt;24&lt;/sub&gt;) are highly reactive biogenic volatile organic compounds playing an important role in atmospheric chemistry. Once emitted from the Earth&amp;#8217;s surface, primarily by vegetation, they are rapidly oxidized to semivolatile oxygenated organic species that can lead to secondary organic aerosols (SOA) that influence climate. In the pristine Amazon rainforest environment oxidation of sesquiterpenes is initiated by OH and ozone.&lt;/p&gt;&lt;p&gt;We measured sesquiterpenes in March 2018 (wet season) and November 2018 (dry season) from central Amazonia, at the remote field site ATTO (Amazonian Tall Tower Observatory), Brazil. Samples were collected on adsorbent filled tubes equipped with ozone scrubbers at different heights above the forest canopy&amp;#160;;&amp;#160;every three hours for two weeks at 80m and 150m (wet season) and every hour for three days at 80m, 150m and 320m (dry season). Samples were then analysed in the&amp;#160;laboratory with a TD-GC-TOF-MS (Thermodesorption-Gas Chromatographer-Time Of Flight-Mass Spectrometer, Markes International). Simultaneous measurements of ozone and meteorological parameters were made at the nearby INSTANT tower. Identification of the chromatographic peaks was achieved by injection of standard molecules and by matching literature mass spectra. Quantification of the chemical compounds was achieved by injection of a standard mixture containing terpenes.The most abundant sesquiterpene measured at ATTO is (-)-&amp;#945;-copaene. Its diel profile varies with photosynthetically active radiation (PAR) and temperature, suggesting the canopy to be the main emission source. Interestingly, other identified sesquiterpenes show a consistent mirrored cycle, with their concentration being higher by night than by day. These varied mostly with RH suggesting the soil to be the main source of the emissions. Air samples taken at the ground are qualitatively and quantitatively different to those collected at different altitudes from the tower. Sesquiterpenes show a common maximum at sunrise (5&amp;#160;:00-7&amp;#160;:00 local time, UTC-4h) coincident with a strong decrease in ozone concentration (&gt;50% decrease on average during the dry season). The strongest effect is registered during the dry season, when sesquiterpenes and ozone concentrations are highest and ozone loss is largest. The atmospheric impact of the measured sesquiterpenes will be discussed including ozone reactivity contributions and OH generation.&lt;/p&gt;

scholarly journals Cool season precipitation projections for California and the Western United States in NA-CORDEX models

2021 ◽  
Author(s):  
Kelly Mahoney ◽  
James D. Scott ◽  
Michael Alexander ◽  
Rachel McCrary ◽  
Mimi Hughes ◽  
...  
Keyword(s):  
United States ◽  
Climate Models ◽  
Snow Water Equivalent ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Western United States ◽  
Monthly Precipitation ◽  
Wet Season ◽  
Cool Season ◽  
Projected Change

AbstractUnderstanding future precipitation changes is critical for water supply and flood risk applications in the western United States. The North American COordinated Regional Downscaling EXperiment (NA-CORDEX) matrix of global and regional climate models at multiple resolutions (~ 50-km and 25-km grid spacings) is used to evaluate mean monthly precipitation, extreme daily precipitation, and snow water equivalent (SWE) over the western United States, with a sub-regional focus on California. Results indicate significant model spread in mean monthly precipitation in several key water-sensitive areas in both historical and future projections, but suggest model agreement on increasing daily extreme precipitation magnitudes, decreasing seasonal snowpack, and a shortening of the wet season in California in particular. While the beginning and end of the California cool season are projected to dry according to most models, the core of the cool season (December, January, February) shows an overall wetter projected change pattern. Daily cool-season precipitation extremes generally increase for most models, particularly in California in the mid-winter months. Finally, a marked projected decrease in future seasonal SWE is found across all models, accompanied by earlier dates of maximum seasonal SWE, and thus a shortening of the period of snow cover as well. Results are discussed in the context of how the diverse model membership and variable resolutions offered by the NA-CORDEX ensemble can be best leveraged by stakeholders faced with future water planning challenges.

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