scholarly journals Simulations of organic aerosol concentrations during springtime in the Guanzhong Basin, China

2016 ◽  
Vol 16 (15) ◽  
pp. 10045-10061 ◽  
Author(s):  
Tian Feng ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Zhenxing Shen ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Surface Ozone ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Basis Set ◽  
Near Surface ◽  
Guanzhong Basin ◽  
Surrounding Areas ◽  
Background Area

Abstract. The organic aerosol (OA) concentration is simulated in the Guanzhong Basin, China from 23 to 25 April 2013 utilizing the WRF-CHEM model. Two approaches are used to predict OA concentrations: (1) a traditional secondary organic aerosol (SOA) module; (2) a non-traditional SOA module including the volatility basis-set modeling method in which primary organic aerosol (POA) is assumed to be semivolatile and photochemically reactive. Generally, the spatial patterns and temporal variations of the calculated hourly near-surface ozone and fine particle matters agree well with the observations in Xi'an and surrounding areas. The model also yields reasonable distributions of daily PM2.5 and elemental carbon (EC) compared to the filter measurements at 29 sites in the basin. Filter-measured organic carbon (OC) and EC are used to evaluate OA, POA, and SOA using the OC ∕ EC ratio approach. Compared with the traditional SOA module, the non-traditional module significantly improves SOA simulations and explains about 88 % of the observed SOA concentration. Oxidation and partitioning of POA treated as semivolatile constitute the most important pathway for the SOA formation, contributing more than 75 % of the SOA concentrations in the basin. Residential emissions are the dominant anthropogenic OA source, constituting about 50 % of OA concentrations in urban and rural areas and 30 % in the background area. The OA contribution from transportation emissions decreases from 25 % in urban areas to 20 % in the background area, and the industry emission OA contribution is less than 6 %.

scholarly journals Simulations of Organic Aerosol Concentrations during Springtime in the Guanzhong Basin, China

2016 ◽  
Author(s):  
Tian Feng ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Zhenxing Shen ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Surface Ozone ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Basis Set ◽  
Air Pollution Control ◽  
Near Surface ◽  
Guanzhong Basin ◽  
Background Area

Abstract. The organic aerosol (OA) concentration is simulated in the Guanzhong basin, China from 23 to 25 April 2013 utilizing the WRF-CHEM model. Two approaches are used to predict OA concentrations: (1) a traditional secondary organic aerosol (SOA) module; (2) a non-traditional SOA module including the volatility basis-set modeling method in which primary organic aerosols (POA) are assumed to be semi-volatile and photochemically reactive. Generally, the spatial patterns and temporal variations of the calculated hourly near-surface ozone and fine particle matters agree well with the observations in Xi’an and surrounding areas. The model also yields reasonable distributions of daily PM2.5 and elemental carbon (EC) compared to the filter measurements at 29 sites in the basin. Filter measured organic carbon (OC) and EC are used to evaluate OA, POA, and SOA using the OC / EC ratio approach. Compared with the traditional SOA module, the non-traditional module significantly improves SOA simulations and explains about 88 % of the observed SOA concentration. Oxidation and partitioning of POA treated as semi-volatile constitute the most important pathway for the SOA formation, contributing more than 75 % of the SOA concentrations in the basin. Residential emissions are the dominant anthropogenic OA source, constituting about 50 % of OA concentrations in urban and rural areas and 30 % in the background area. The OA contribution from transportation emissions decreases from 25 % in urban areas to 20 % in the background area, and the industry emission OA contribution is less than 6 %. The simulation results will facilitate the design of the air pollution control strategies in the basin.

scholarly journals Analyses of Nocturnal Temperature Cooling-Rate Response to Historical Local-Scale Urban Land-Use/Land Cover Change

2011 ◽  
Vol 50 (9) ◽  
pp. 1872-1883 ◽  
Author(s):  
Winston T. L. Chow ◽  
Bohumil M. Svoma
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Cooling Rate ◽  
Rural Areas ◽  
Urban Areas ◽  
Local Scale ◽  
Urban Land Use ◽  
Cooling Rates ◽  
Near Surface ◽  
Over Time

AbstractUrbanization affects near-surface climates by increasing city temperatures relative to rural temperatures [i.e., the urban heat island (UHI) effect]. This effect is usually measured as the relative temperature difference between urban areas and a rural location. Use of this measure is potentially problematic, however, mainly because of unclear “rural” definitions across different cities. An alternative metric is proposed—surface temperature cooling/warming rates—that directly measures how variations in land-use and land cover (LULC) affect temperatures for a specific urban area. In this study, the impact of local-scale (<1 km2), historical LULC change was examined on near-surface nocturnal meteorological station temperatures sited within metropolitan Phoenix, Arizona, for 1) urban versus rural areas, 2) areas that underwent rural-to-urban transition over a 20-yr period, and 3) different seasons. Temperature data were analyzed during ideal synoptic conditions of clear and calm weather that do not inhibit surface cooling and that also qualified with respect to measured near-surface wind impacts. Results indicated that 1) urban areas generally observed lower cooling-rate magnitudes than did rural areas, 2) urbanization significantly reduced cooling rates over time, and 3) mean cooling-rate magnitudes were typically larger in summer than in winter. Significant variations in mean nocturnal urban wind speeds were also observed over time, suggesting a possible UHI-induced circulation system that may have influenced local-scale station cooling rates.

Simulation of the Cooking Organic Aerosol Concentration Variability in an Urban Area

2021 ◽  
Author(s):  
Evangelia Siouti ◽  
Ksakousti Skyllakou ◽  
Ioannis Kioutsioukis ◽  
Giancarlo Ciarelli ◽  
Spyros N. Pandis
Keyword(s):  
Urban Area ◽  
Urban Areas ◽  
Temporal Distribution ◽  
Late Summer ◽  
Field Studies ◽  
Organic Aerosol ◽  
Basis Set ◽  
Cooking Times ◽  
The City ◽  
Lunch Time

&lt;p&gt;Cooking operations can be an important fine PM source for urban areas. Cooking emissions are a source of pollution that has been often ignored and are not included or are seriously underestimated in urban emission inventories. However, several field studies in cities all over Europe suggest that cooking organic aerosol (COA) can be an important component of the total organic PM. In this study we propose and evaluate a methodology for the simulation of the COA concentration and its variability in space and time in an urban area. The city of Patras, the third biggest in Greece is used for this first application for a typical late summer period. The spatial distribution of COA emissions is based on the exact location of restaurants and grills, while the emissions on the meat consumption in Greece. We estimated COA emissions of 150 kg d&lt;sup&gt;-1&lt;/sup&gt; that corresponds to 0.6 g d&lt;sup&gt;-1&lt;/sup&gt; per person. The temporal distribution of COA was based on the known cooking times and the results of the past field studies in the area. Half of the daily COA is emitted during dinner time (21:00-0:00 LT), while approximately 25% during lunch time (13:00-16:00 LT). The COA is simulated using the Volatility Basis Set with a volatility distribution measured in the laboratory and is treated as semivolatile and reactive. The maximum average COA concentration during the simulation period is predicted to be 1.3 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt; in a mainly pedestrian area with a high density of restaurants. Peak hourly COA concentrations in this area exceed 10 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt; during several nights. The local production of secondary COA is predicted to be slow and it represents just a few percent of the total COA.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Model simulations of cooking organic aerosol (COA) over the UK using estimates of emissions based on measurements at two sites in London

2016 ◽  
Vol 16 (21) ◽  
pp. 13773-13789 ◽  
Author(s):  
Riinu Ots ◽  
Massimo Vieno ◽  
James D. Allan ◽  
Stefan Reis ◽  
Eiko Nemitz ◽  
...  
Keyword(s):  
Population Density ◽  
Atmospheric Chemistry ◽  
Rural Areas ◽  
Urban Areas ◽  
Census Data ◽  
Organic Aerosol ◽  
Balance Model ◽  
Rural Site ◽  
Annual Average ◽  
The Uk

Abstract. Cooking organic aerosol (COA) is currently not included in European emission inventories. However, recent positive matrix factorization (PMF) analyses of aerosol mass spectrometer (AMS) measurements have suggested important contributions of COA in several European cities. In this study, emissions of COA were estimated for the UK, based on hourly AMS measurements of COA made at two sites in London (a kerbside site in central London and an urban background site in a residential area close to central London) for the full calendar year of 2012 during the Clean Air for London (ClearfLo) campaign. Iteration of COA emissions estimates and subsequent evaluation and sensitivity experiments were conducted with the EMEP4UK atmospheric chemistry transport modelling system with a horizontal resolution of 5 km  ×  5 km. The spatial distribution of these emissions was based on workday population density derived from the 2011 census data. The estimated UK annual COA emission was 7.4 Gg per year, which is an almost 10 % addition to the officially reported UK national total anthropogenic emissions of PM2.5 (82 Gg in 2012), corresponding to 320 mg person−1 day−1 on average. Weekday and weekend diurnal variation in COA emissions were also based on the AMS measurements. Modelled concentrations of COA were then independently evaluated against AMS-derived COA measurements from another city and time period (Manchester, January–February 2007), as well as with COA estimated by a chemical mass balance model of measurements for a 2-week period at the Harwell rural site (∼ 80 km west of central London). The modelled annual average contribution of COA to ambient particulate matter (PM) in central London was between 1 and 2 µg m−3 (∼ 20 % of total measured OA1) and between 0.5 and 0.7 µg m−3 in other major cities in England (Manchester, Birmingham, Leeds). It was also shown that cities smaller than London can have a central hotspot of population density of smaller area than the computational grid cell, in which case higher localized COA concentrations than modelled here may be expected. Modelled COA concentrations dropped rapidly outside of major urban areas (annual average of 0.12 µg m−3 for the Harwell location), indicating that although COA can be a notable component in urban air, it does not have a significant effect on PM concentrations on rural areas. The possibility that the AMS-PMF apportionment measurements overestimate COA concentrations by up to a factor of 2 is discussed. Since COA is a primary emission, any downward adjustments in COA emissions would lead to a proportional linear downward scaling in the absolute magnitudes of COA concentrations simulated in the model.

scholarly journals The Sensitivity of Urban Meteorology to Soil Moisture Boundary Conditions: A Case Study in Melbourne, Australia

2017 ◽  
Vol 56 (8) ◽  
pp. 2155-2172 ◽  
Author(s):  
Stephanie J. Jacobs ◽  
Ailie J. E. Gallant ◽  
Nigel J. Tapper
Keyword(s):  
Soil Moisture ◽  
Rural Areas ◽  
Urban Areas ◽  
Maximum Temperature ◽  
Weather Research And Forecasting ◽  
Near Surface ◽  
Australian Water ◽  
Surface Temperatures ◽  
Order Of Magnitude

AbstractThe sensitivity of near-surface urban meteorological conditions to three different soil moisture initialization experiments under heat-wave conditions is investigated for the city of Melbourne, Australia. The Weather Research and Forecasting Model is used to simulate a domain over Melbourne and its surrounding rural areas. The experiments employ three suites of simulations. Two suites initialize the model with soil moisture from the top layer of the ERA-Interim soil moisture data with a 3-month and 24-h coupled spinup period, respectively. The third suite initializes the model with the arguably more realistic soil moistures from the Australian Water Availability Project (AWAP), which are an order of magnitude drier than the ERA-Interim data, again using a 24-h spinup period. The simulations employing the AWAP data are found to have smaller errors when compared with observations, with biases in urban maximum temperature reduced by 4.1°C and biases in the skin temperature reduced by 3.0°C relative to the biases of the 3-month-spinup experiment. Despite urban areas only having a small proportion of soil-covered surfaces, the results show that urban soils have a greater influence on urban near-surface temperatures at night, whereas rural soils have a greater influence on urban near-surface temperatures during the daytime.

scholarly journals Summertime ozone formation in Xi'an and surrounding areas, China

2015 ◽  
Vol 15 (21) ◽  
pp. 30563-30608 ◽  
Author(s):  
T. Feng ◽  
N. Bei ◽  
R. Huang ◽  
J. Cao ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Control Strategies ◽  
Surface Wind ◽  
Temporal Variations ◽  
Anthropogenic Sources ◽  
Anthropogenic Emissions ◽  
Near Surface ◽  
Production Regime ◽  
High Concentrations ◽  
Surrounding Areas ◽  
Surface O3

Abstract. In the study, the ozone (O3) formation is investigated in Xi'an and surrounding areas, China using the WRF-CHEM model during the period from 22 to 24 August 2013 corresponding to a heavy air pollution episode with high concentrations of O3 and PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm). The WRF-CHEM model generally performs well in simulating the surface temperature and relative humidity compared to the observations and also reasonably reproduces the observed temporal variations of the surface wind speed and direction. The convergence formed in Xi'an and surrounding areas is favorable for the accumulation of pollutants, causing high concentrations of O3 and PM2.5. In general, the calculated spatial patterns and temporal variations of near-surface O3 and PM2.5 are consistent well with the measurement at the ambient monitoring stations. The simulated daily mass concentrations of aerosol constituents, including sulfate, nitrate, ammonium, elemental and organic carbon, are also in good agreement with the filter measurements. High aerosol concentrations in Xi'an and surrounding areas significantly decrease the photolysis frequencies and can reduce near-surface O3 concentrations by more than 50 μg m−3 (around 25 ppb) on average. Sensitivity studies show that the O3 production regime in Xi'an and surrounding areas is complicated, varying from NOx to VOC-sensitive chemistry. The industry emissions contribute the most to the O3 concentrations compared to the natural and other anthropogenic sources, but still do not play a determined role in the O3 formation. The complicated O3 production regime and high aerosol levels constitute a dilemma for O3 control strategies in Xi'an and surrounding areas. In the condition with high O3 and PM2.5 concentrations, decreasing various anthropogenic emissions cannot efficiently mitigate the O3 pollution, and a 50 % reduction of all the anthropogenic emissions only decreases near-surface O3 concentrations by less than 14 % during daytime. Further studies need to be performed for O3 control strategies considering manifest changes of the emission inventory and uncertainties of meteorological field simulations.

scholarly journals Drivers and Projections of Global Surface Temperature Anomalies at Sub-City Scale

2021 ◽  
Author(s):  
Susanne A. Benz ◽  
Steven J. Davis ◽  
Jennifer Burney
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Rural Areas ◽  
Urban Areas ◽  
Surface Energy Balance ◽  
Urban Migration ◽  
Data Set ◽  
Surface Temperatures ◽  
Summer Temperatures ◽  
Surrounding Areas

More than half of the world’s population now lives in urban areas, and trends in rural-to-urban migration are expected to continue through the end of the century. Although cities create efficiencies that drive innovation and economic growth, they also alter the local surface energy balance, resulting in urban temperatures that can differ dramatically from surrounding areas. Here we introduce a global 1-km resolution data set of seasonal and diurnal anomalies in urban surface temperatures relative to their rural surroundings, and use satellite-observable parameters in a simple model informed by the surface energy balance to understand the dominant drivers of present urban heating, the heat-related impacts of projected future urbanization, and the potential for policies to mitigate those damages. At present, urban populations live in areas with daytime surface summer temperatures that are 3.21°C (-3.97 - 9.24, 5th-95th percentiles) warmer than surrounding rural areas, such that 1.2 billion people are exposed to average surface summer temperatures in excess of 35°C that might put them at risk of heat-related illness. If design and infrastructure of cities remain unchanged, increased urban heat anomalies will add 0.19°C (-0.01, 0.47) to the daytime summer surface temperatures in urban areas in 2100 -- in addition to warming due to climate change. Such urban heating will increase the number of urban population living under extreme and potentially health-threatening temperatures by approximately 20% compared to current numbers. However we also find a significant potential for mitigation: 82% of all urban areas can optimize vegetation and/or surface albedo and reduce urban daytime summer surface temperatures for the affected population on average by -0.81°C (-2.55, -0.05).

scholarly journals Volatility basis-set approach simulation of organic aerosol formation in East Asia: implications for anthropogenic-biogenic interaction and controllable amounts

2014 ◽  
Vol 14 (5) ◽  
pp. 6203-6260 ◽  
Author(s):  
H. Matsui ◽  
M. Koike ◽  
Y. Kondo ◽  
A. Takami ◽  
J. D. Fast ◽  
...  
Keyword(s):  
East Asia ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Basis Set ◽  
Anthropogenic Sources ◽  
Aerosol Formation ◽  
Organic Vapors ◽  
Mass Spectrometers ◽  
High Fraction ◽  
Outflow Region

Abstract. Organic aerosol (OA) simulations using the volatility basis-set approach were made for East Asia and its outflow region. Model simulations were evaluated through comparisons with OA measured by aerosol mass spectrometers in and around Tokyo (at Komaba and Kisai in summer 2003 and 2004) and over the outflow region in East Asia (at Fukue and Hedo in spring 2009). The simulations with aging processes of organic vapors reasonably well reproduced mass concentrations, temporal variations, and formation efficiency of observed OA at all sites. As OA mass was severely underestimated in the simulations without the aging processes, the oxidations of organic vapors are essential for reasonable OA simulations over East Asia. By considering the aging processes, simulated OA concentrations increased from 0.24 to 1.28 μg m−3 in the boundary layer over the whole of East Asia. OA formed from the interaction of anthropogenic and biogenic sources was also enhanced by the aging processes. The fraction of controllable OA was estimated to be 87% of total OA over the whole of East Asia, showing that most of the OA in our simulations formed anthropogenically (controllable). Even a large portion of biogenic secondary OA (78% of biogenic secondary OA) was formed through the influence of anthropogenic sources. The high fraction of controllable OA in our simulations is likely because anthropogenic emissions are dominant over East Asia and OA formation is enhanced by anthropogenic sources and their aging processes. Both the amounts (from 0.18 to 1.12 μg m−3) and the fraction (from 75% to 87%) of controllable OA were increased by aging processes of organic vapors over East Asia.

scholarly journals Modeling organic aerosol over Europe in summer conditions with the VBS-GECKO parameterization: sensitivity to secondary organic compound properties and IVOC (intermediate-volatility organic compound) emissions

2020 ◽  
Vol 20 (8) ◽  
pp. 4905-4931 ◽  
Author(s):  
Victor Lannuque ◽  
Florian Couvidat ◽  
Marie Camredon ◽  
Bernard Aumont ◽  
Bertrand Bessagnet
Keyword(s):  
Organic Compound ◽  
Urban Areas ◽  
Transport Model ◽  
Organic Aerosol ◽  
Basis Set ◽  
Anthropogenic Sources ◽  
Continental Scale ◽  
Model Configuration ◽  
Aging Rates ◽  
Terpene Oxidation

Abstract. The VBS-GECKO (volatility basis set – Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) parameterization for secondary organic aerosol (SOA) formation was integrated into the chemistry-transport model CHIMERE. Concentrations of organic aerosol (OA) and SOA were simulated over Europe for the July–August 2013 period. Simulated concentrations with VBS-GECKO were compared to results obtained with the former H2O parameterization implemented in CHIMERE and to observations from EMEP, ACTRIS and other observations available in the EBAS database. The model configuration using the VBS-GECKO parameterization slightly improves the performances compared to the model configuration using the former H2O parameterization. The VBS-GECKO model configuration performs well for stations showing a large SOA concentration from biogenic sources, especially in northern Europe, but underestimates OA concentrations over stations close to urban areas. Simulated OA was found to be mainly secondary (∼85 %) and from terpene oxidation. Simulations show negligible contribution of the oxidation of mono-aromatic compounds to SOA production. Tests performed to examine the sensitivity of simulated OA concentrations to hydro-solubility, volatility, aging rates and NOx regime have shown that the VBS-GECKO parameterization provides consistent results, with a weak sensitivity to changes in the parameters provided by the gas-phase mechanism included in CHIMERE (e.g., HOx or NOx concentrations). Different scenarios considering intermediate-volatility organic compound (IVOC) emissions were tested to examine the contribution of IVOC oxidation to SOA production. At the continental scale, these simulations show a weak sensitivity of OA concentrations to IVOC emission variations. At the local scale, accounting for IVOC emissions was found to lead to a substantial increase in OA concentrations in the plume from urban areas. This additional OA source remains too small to explain the gap between simulated and measured values at stations where anthropogenic sources are dominant.

scholarly journals The surface aerosol optical properties in urban areas of Nanjing, west Yangtze River Delta of China

2016 ◽  
Author(s):  
B. L. Zhuang ◽  
T. J. Wang ◽  
J. Liu ◽  
S. Li ◽  
M. Xie ◽  
...  
Keyword(s):  
Optical Properties ◽  
Urban Areas ◽  
Radiative Forcing ◽  
Early Morning ◽  
Single Scattering ◽  
Temporal Variations ◽  
Yangtze River Delta ◽  
Aerosol Optical Properties ◽  
Growth Trend ◽  
Near Surface

Abstract. Observational studies of aerosol optical properties are useful to reducing uncertainties in estimating aerosol radiative forcing and forecasting visibility. In this study, the observed near-surface aerosol optical properties in urban Nanjing are analyzed from Mar 2014 to Feb 2016. Results show that near-surface urban aerosols in Nanjing are mainly from local emissions and the regions around. They have lower loadings but are more scattering than in most cities in China. The annual mean aerosol extinction coefficient (EC), single scattering albedo (SSA) and asymmetry parameter (ASP) at 550 nm are 381.96 Mm−1, 0.9 and 0.57, respectively. The aerosol absorption coefficient (AAC) is about one order of magnitude smaller than its scattering coefficient (SC). However, the absorbing aerosol has larger Ångström exponent (AAE) value, 1.58 at 470/660 nm, about 0.2 larger than the scattering aerosols' (SAE). All the aerosol optical properties followed a near unimodal pattern, the ranges around their averages accounting for more than 60 % of the total samplings. Additionally, they have substantial seasonality and diurnal variations. High levels of SC and AAC all appear in winter due to higher aerosol and trace gas emissions. AAE (ASP) is the smallest (largest) in summer because of high relative humidity (RH) which also causes considerably larger SC and smaller SAE, although intensive gas-to-particle transformation could produce a large number of finer scattering aerosols in this season. Seasonality of EC is different from the columnar aerosol optical depth. Larger AACs appear at the rush hours of the day while SC and Bsp only peak in the early morning. Aerosols are fresher at daytime than at nighttime, leading to their larger AE and smaller ASP. Different temporal variations between AAC and SC cause the aerosols more absorbing (smaller SSA) in autumn and around rush hours. ASP has a good quasi-LogNormal growth trend with increasing SC when RH is below 60 %. The correlation between AAC and SC at the site is close but a little smaller than that in suburban Nanjing in spring. Atmospheric visibility decreases exponentially with increasing EC or SC, more sharply in spring and summer. It could be further deteriorated with increasing SSA and ASP.

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