scholarly journals Influence of the aerosol solar extinction on photochemistry during the 2010 Russian wildfires episode

2015 ◽  
Vol 15 (19) ◽  
pp. 10983-10998 ◽  
Author(s):  
J. C. Péré ◽  
B. Bessagnet ◽  
V. Pont ◽  
M. Mallet ◽  
F. Minvielle
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Model Performance ◽  
Surface Concentration ◽  
Near Surface ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Air Quality Measurements ◽  
Photolysis Rates ◽  
Optical Module

Abstract. In this work, impact of aerosol solar extinction on the photochemistry over eastern Europe during the 2010 wildfires episode is discussed for the period from 5 to 12 August 2010, which coincides to the peak of fire activity. The methodology is based on an online coupling between the chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code TUV. Results of simulations indicate an important influence of the aerosol solar extinction, in terms of intensity and spatial extent, with a reduction of the photolysis rates of NO2 and O3 up to 50 % (in daytime average) along the aerosol plume transport. At a regional scale, these changes in photolysis rates lead to a 3–15 % increase in the NO2 daytime concentration and to an ozone reduction near the surface of 1–12 %. The ozone reduction is shown to occur over the entire boundary layer, where aerosols are located. Also, the total aerosol mass concentration (PM10) is shown to be decreased by 1–2 %, on average during the studied period, caused by a reduced formation of secondary aerosols such as sulfates and secondary organics (4–10 %) when aerosol impact on photolysis rates is included. In terms of model performance, comparisons of simulations with air quality measurements at Moscow indicate that an explicit representation of aerosols interaction with photolysis rates tend to improve the estimation of the near-surface concentration of ozone and nitrogen dioxide as well as the formation of inorganic aerosol species such as ammonium, nitrates and sulfates.

scholarly journals Influence of the aerosol solar extinction on photochemistry during the 2010 Russian wildfires episode

2015 ◽  
Vol 15 (5) ◽  
pp. 7057-7087
Author(s):  
J. C. Péré ◽  
B. Bessagnet ◽  
V. Pont ◽  
M. Mallet ◽  
F. Minvielle
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Peak Reduction ◽  
Air Quality Prediction ◽  
Aerosol Mass Concentration ◽  
Air Quality Measurements ◽  
Photolysis Rates ◽  
Optical Module ◽  
Alert Threshold

Abstract. In this work, impact of aerosol solar extinction on the photochemistry over eastern Europe during the 2010 wildfires episode is discussed for the period from 5 to 12 August 2010, which coincides to the peak of fire activity. The methodology is based on an on-line coupling between the chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code TUV. Results of simulations indicate an important influence of the aerosol solar extinction, in terms of intensity and spatial extent, with a reduction of the photolysis rates of NO2 and O3 up to 50% (in diurnal-averaged) along the aerosol plume transport. At a regional scale, these changes in photolysis rates lead to a 3–15% increase in the NO2 daytime concentration and to an ozone reduction near the surface of 1–12%. The ozone reduction is shown to occur over the entire boundary layer, where aerosols are located. Also, comparisons of simulations with air quality measurements over Moscow show that the inclusion of the aerosol feedback tends to slightly improve performance of the model in simulating NO2 and O3 ground concentrations. In term of air quality prediction, the O3 peak reduction when including aerosol feedback results in a non-negligible difference in the predicted exceedance of alert threshold compared to the simulation without aerosol feedback, in coherence with measurements. Finally, the total aerosol mass concentration (PM10) is shown to be decreased by 1–2 %, on average during the studied period, caused by a reduced formation of secondary aerosols such as sulphates and secondary organics (4–10%) when aerosol impact on photolysis rates is included.

scholarly journals Multi-species inversion of CH<sub>4</sub>, CO and H<sub>2</sub> emissions from surface measurements

2009 ◽  
Vol 9 (14) ◽  
pp. 5281-5297 ◽  
Author(s):  
I. Pison ◽  
P. Bousquet ◽  
F. Chevallier ◽  
S. Szopa ◽  
D. Hauglustaine
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Surface Concentration ◽  
Temporal Variations ◽  
Global Scale ◽  
Chemical Transport Model ◽  
Methyl Chloroform ◽  
Emission Fluxes ◽  
Surface Measurements ◽  
One Year

Abstract. In order to study the spatial and temporal variations of the emissions of greenhouse gases and of their precursors, we developed a data assimilation system and applied it to infer emissions of CH4, CO and H2 for one year. It is based on an atmospheric chemical transport model and on a simplified scheme for the oxidation chain of hydrocarbons, including methane, formaldehyde, carbon monoxide and molecular hydrogen together with methyl chloroform. The methodology is exposed and a first attempt at evaluating the inverted fluxes is made. Inversions of the emission fluxes of CO, CH4 and H2 and concentrations of HCHO and OH were performed for the year 2004, using surface concentration measurements of CO, CH4, H2 and CH3CCl3 as constraints. Independent data from ship and aircraft measurements and satellite retrievals are used to evaluate the results. The total emitted mass of CO is 30% higher after the inversion, due to increased fluxes by up to 35% in the Northern Hemisphere. The spatial distribution of emissions of CH4 is modified by a decrease of fluxes in boreal areas up to 60%. The comparison between mono- and multi-species inversions shows that the results are close at a global scale but may significantly differ at a regional scale because of the interactions between the various tracers during the inversion.

scholarly journals Representing the effects of stratosphere–troposphere exchange on 3-D O<sub>3</sub> distributions in chemistry transport models using a potential vorticity-based parameterization

2016 ◽  
Vol 16 (17) ◽  
pp. 10865-10877 ◽  
Author(s):  
Jia Xing ◽  
Rohit Mathur ◽  
Jonathan Pleim ◽  
Christian Hogrefe ◽  
Jiandong Wang ◽  
...  
Keyword(s):  
Potential Vorticity ◽  
Transport Model ◽  
Model Performance ◽  
Surface Concentration ◽  
Weather Research And Forecasting ◽  
Regional Models ◽  
Transport Models ◽  
Reference Case ◽  
Chemistry Transport Model ◽  
Spatially Varying

Abstract. Downward transport of ozone (O3) from the stratosphere can be a significant contributor to tropospheric O3 background levels. However, this process often is not well represented in current regional models. In this study, we develop a seasonally and spatially varying potential vorticity (PV)-based function to parameterize upper tropospheric and/or lower stratospheric (UTLS) O3 in a chemistry transport model. This dynamic O3–PV function is developed based on 21-year ozonesonde records from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) with corresponding PV values from a 21-year Weather Research and Forecasting (WRF) simulation across the Northern Hemisphere from 1990 to 2010. The result suggests strong spatial and seasonal variations of O3 ∕ PV ratios which exhibits large values in the upper layers and in high-latitude regions, with highest values in spring and the lowest values in autumn over an annual cycle. The newly developed O3 ∕ PV function was then applied in the Community Multiscale Air Quality (CMAQ) model for an annual simulation of the year 2006. The simulated UTLS O3 agrees much better with observations in both magnitude and seasonality after the implementation of the new parameterization. Considerable impacts on surface O3 model performance were found in the comparison with observations from three observational networks, i.e., EMEP, CASTNET and WDCGG. With the new parameterization, the negative bias in spring is reduced from −20 to −15 % in the reference case to −9 to −1 %, while the positive bias in autumn is increased from 1 to 15 % in the reference case to 5 to 22 %. Therefore, the downward transport of O3 from upper layers has large impacts on surface concentration and needs to be properly represented in regional models.

scholarly journals Clouds, photolysis and regional tropospheric ozone budgets

2009 ◽  
Vol 9 (3) ◽  
pp. 13889-13916 ◽  
Author(s):  
A. Voulgarakis ◽  
O. Wild ◽  
N. H. Savage ◽  
G. D. Carver ◽  
J. A. Pyle
Keyword(s):  
Tropospheric Ozone ◽  
Large Scale ◽  
Transport Model ◽  
Regional Scale ◽  
Three Dimensional ◽  
Global Scale ◽  
Chemical Production ◽  
Chemical Transport Model ◽  
Photolysis Rates ◽  
Boundary Layer Ozone

Abstract. We use a three-dimensional chemical transport model to examine the shortwave radiative effects of clouds on the tropospheric ozone budget. In addition to looking at changes in global concentrations as previous studies have done, we examine changes in ozone chemical production and loss caused by clouds and how these vary in different parts of the troposphere. On a global scale, we find that clouds have a modest effect on ozone chemistry, but on a regional scale their role is much more significant, with the size of the response dependent on the region. The largest averaged changes in chemical budgets (±10–14%) are found in the marine troposphere, where cloud optical depths are high. We demonstrate that cloud effects are small on average in the middle troposphere because this is a transition region between reduction and enhancement in photolysis rates. We show that increases in boundary layer ozone due to clouds are driven by large-scale changes in downward ozone transport from higher in the troposphere rather than by decreases in in-situ ozone chemical loss rates. Increases in upper tropospheric ozone are caused by higher production rates due to backscattering of radiation and consequent increases in photolysis rates, mainly J(NO2). The global radiative effect of clouds on isoprene is stronger than on ozone. Tropospheric isoprene lifetime increases by 7% when taking clouds into account. We compare the importance of clouds in contributing to uncertainties in the global ozone budget with the role of other radiatively-important factors. The budget is most sensitive to the overhead ozone column, while surface albedo and clouds have smaller effects. However, uncertainty in representing the spatial distribution of clouds may lead to a large sensitivity on regional scales.

scholarly journals Size distribution of near-surface aerosols and its relation to the columnar aerosol optical depths

2004 ◽  
Vol 22 (10) ◽  
pp. 3347-3351 ◽  
Author(s):  
P. S. Pillai ◽  
K. Krishna Moorthy
Keyword(s):  
Size Distribution ◽  
Quartz Crystal Microbalance ◽  
Relative Abundance ◽  
Mass Concentration ◽  
Quartz Crystal ◽  
Near Surface ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Multi Wavelength ◽  
Aerosol Properties

Abstract. Simultaneous data on Aerosol Optical Depth (AOD) and size segregated, near-surface, aerosol mass concentration was obtained from a Multi wavelength Solar Radiometer (MWR) and Quartz Crystal Microbalance Impactor (QCM), respectively. These were used to examine the association between near-surface aerosol properties and columnar AOD. The spectral AODs were approximated to the Ångström relation τp=βλ-α, and the wavelength exponent α and turbidity coefficient β have been obtained. In general, α was found to be well associated with the relative abundance of accumulation mode aerosols (estimated from the simultaneous QCM data) while β followed the variations of the coarse mode aerosol mass concentration; the association being closer during periods of continental airmass.

scholarly journals Model evaluation of marine primary organic aerosol emission schemes

2012 ◽  
Vol 12 (18) ◽  
pp. 8553-8566 ◽  
Author(s):  
B. Gantt ◽  
M. S. Johnson ◽  
N. Meskhidze ◽  
J. Sciare ◽  
J. Ovadnevaite ◽  
...  
Keyword(s):  
Model Comparison ◽  
Transport Model ◽  
Organic Aerosol ◽  
Sea Spray ◽  
Mean Values ◽  
Chl A ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Emission ◽  
Sea Spray Aerosol

Abstract. In this study, several marine primary organic aerosol (POA) emission schemes have been evaluated using the GEOS-Chem chemical transport model in order to provide guidance for their implementation in air quality and climate models. These emission schemes, based on varying dependencies of chlorophyll a concentration ([chl a]) and 10 m wind speed (U10), have large differences in their magnitude, spatial distribution, and seasonality. Model comparison with weekly and monthly mean values of the organic aerosol mass concentration at two coastal sites shows that the source function exclusively related to [chl a] does a better job replicating surface observations. Sensitivity simulations in which the negative U10 and positive [chl a] dependence of the organic mass fraction of sea spray aerosol are enhanced show improved prediction of the seasonality of the marine POA concentrations. A top-down estimate of submicron marine POA emissions based on the parameterization that compares best to the observed weekly and monthly mean values of marine organic aerosol surface concentrations has a global average emission rate of 6.3 Tg yr−1. Evaluation of existing marine POA source functions against a case study during which marine POA contributed the major fraction of submicron aerosol mass shows that none of the existing parameterizations are able to reproduce the hourly-averaged observations. Our calculations suggest that in order to capture episodic events and short-term variability in submicron marine POA concentration over the ocean, new source functions need to be developed that are grounded in the physical processes unique to the organic fraction of sea spray aerosol.

scholarly journals Development of a three-dimensional variational assimilation system for lidar profile data based on a size-resolved aerosol model in WRF-Chem model v3.9.1 and its application in PM<sub>2.5</sub> forecasts across China

2020 ◽  
Author(s):  
Yanfei Liang ◽  
Zengliang Zang ◽  
Dong Liu ◽  
Peng Yan ◽  
Yiwen Hu ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Three Dimensional ◽  
Initial Field ◽  
Forecast Performance ◽  
Near Surface ◽  
Aerosol Model ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Particulate Matter 2.5 ◽  
Assimilation System

Abstract. For the aerosol variables in the model for simulating aerosol interactions and chemistry (MOSAIC)-4bin chemical scheme in the Weather Research and Forecasting–Chemistry (WRF–Chem) model, this study presents an observation forward aerosol extinction coefficient (AEC) and aerosol mass concentration (AMC) operator and corresponding adjoint based on the interagency monitoring of protected visual environments (IMPROVE) equation, and then a three-dimensional variational (3-DVAR) data assimilation system (DA) is developed for lidar AECs and AMCs. DA experiments are conducted based on AEC profiles measured by five light detection and ranging (lidar) systems as well as mass concentration (MC) data measured at over 1,500 ground environmental monitoring stations across China for particulate matter 2.5 µm or less in diameter (PM2.5) and PM between 2.5 and 10 µm in diameter (PM10). An experiment comparing assimilated and without assimilated measurements finds the following. While only five lidars were available within the simulation region (approximately 2.33 million km2 in size), assimilating lidar AEC data alone can effectively improve the accuracy of the initial field of the WRF–Chem as well as its forecast performance for PM2.5MCs. Compared to the without assimilated experiment, DA reduces the root mean square error of surface PM2.5MCs in the initial field of the model by 10.5 μg/m3 (17.6 %). Moreover, the positive effect resulting from the optimization of the initial field for AMCs can last for more than 24 h. By taking advantage of lidar aerosol vertical profile information and the near-surface PM MC observations, assimilating lidar AEC and surface PM2.5 (PM10) simultaneously can effectively integrate their observed information and generate a more accurate 3D aerosol analysis field.

scholarly journals Modeling organic aerosols during MILAGRO: application of the CHIMERE model and importance of biogenic secondary organic aerosols

2009 ◽  
Vol 9 (3) ◽  
pp. 12207-12281 ◽  
Author(s):  
A. Hodzic ◽  
J. L. Jimenez ◽  
S. Madronich ◽  
A. C. Aiken ◽  
B. Bessagnet ◽  
...  
Keyword(s):  
Mexico City ◽  
Biomass Burning ◽  
Transport Model ◽  
Large Fraction ◽  
Regional Scale ◽  
Organic Aerosols ◽  
Base Case ◽  
Surface Model ◽  
Near Surface ◽  
The City

Abstract. The meso-scale chemistry-transport model CHIMERE is used to assess our understanding of major sources and formation processes leading to a fairly large amount of organic aerosols (OA, including primary OA (POA) and secondary OA (SOA)) observed in Mexico City during the MILAGRO field project (March 2006). Chemical analyses of submicron aerosols from aerosol mass spectrometers (AMS) indicate that organic particles found in the Mexico City basin contain a large fraction of oxygenated organic species (OOA) which have strong correspondence with SOA, and that their production actively continues downwind of the city. The SOA formation is modeled here by the one-step oxidation of anthropogenic (i.e. aromatics, alkanes), biogenic (i.e. monoterpenes and isoprene), and biomass-burning SOA precursors and their partitioning into both organic and aqueous phases. The near-surface model evaluation shows that predicted OA correlates reasonably well with measurements during the campaign, however it remains a factor of 2 lower than the measured total OA. Fairly good agreement is found between predicted and observed POA within the city suggesting that anthropogenic and biomass burning emissions are reasonably captured. Consistent with previous studies in Mexico City, large discrepancies are encountered for SOA, with a factor of 2–10 model underestimate. When only anthropogenic SOA precursors were considered, the model was able to reproduce within a factor of two the sharp increase in SOA concentrations during the late morning at both urban and near-urban locations but the discrepancy increases rapidly later in the day, consistent with previous results, and is especially obvious when the column-integrated SOA mass is considered instead of the surface concentration. The increase in the missing SOA mass in the afternoon coincides with the sharp drop in POA suggesting a tendency of the model to excessively evaporate the freshly formed SOA. Predicted SOA concentrations in our base case were extremely low when photochemistry was not active, especially overnight, as the SOA formed in the previous day was mostly quickly advected away from the basin. These nighttime discrepancies were not significantly reduced when greatly enhanced partitioning to the aerosol phase was assumed. Model sensitivity results suggest that observed nighttime SOA concentrations are strongly influenced by a regional background SOA (~1.5 μg/m3) of biogenic origin which is transported from the coastal mountain ranges into the Mexico City basin. The relative contribution of biogenic SOA to monthly mean modeled SOA levels is estimated to be more than 30% within the city and up to 65–90% at the regional scale (even in the immediate vicinity of the city) which may help explain the significant amount of modern carbon in the aerosols inside the city during low biomass burning periods. The anthropogenic emissions of isoprene and its nighttime oxidation by NO3 were also found to enhance the SOA mean concentrations within the city by an additional 15%. Our results confirm the large underestimation of the SOA production by traditional models in polluted regions (estimated as 10–20 Tons within the Mexico City metropolitan area during the daily peak), and emphasize for the first time the role of biogenic precursors in this region, indicating that they cannot be neglected in modeling studies.

scholarly journals Multi-decadal variations of atmospheric aerosols from 1980 to 2009: sources and regional trends

2013 ◽  
Vol 13 (7) ◽  
pp. 19751-19835 ◽  
Author(s):  
◽  
T. Diehl ◽  
Q. Tan ◽  
J. M. Prospero ◽  
R. A. Kahn ◽  
...  
Keyword(s):  
North Atlantic ◽  
Regional Scale ◽  
Surface Wind ◽  
Dust Emission ◽  
Surface Concentration ◽  
Pollutant Emission ◽  
Near Surface ◽  
Global Average ◽  
Regional Trends ◽  
Tropical North Atlantic

Abstract. Aerosol variations and trends over different land and ocean regions during 1980–2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and observations from multiple satellite sensors and ground-based networks. Excluding time periods with large volcanic influences, the tendency of aerosol optical depth (AOD) and surface concentration over polluted land regions is consistent with the anthropogenic emission changes. The largest reduction occurs over Europe, and regions in North America and Russia also exhibit reductions. On the other hand, East Asia and South Asia show AOD increases, although relatively large amount of natural aerosols in Asia makes the total changes less directly connected to the pollutant emission trends. Over major dust source regions, model analysis indicates that the dust emissions over the Sahara and Sahel respond mainly to the near-surface wind speed, but over Central Asia they are largely influenced by ground wetness. The decreasing dust trend in the tropical North Atlantic is most closely associated with the decrease of Sahel dust emission and increase of precipitation over the tropical North Atlantic, likely driven by the sea surface temperature increase. Despite significant regional trends, the model-calculated global annual average AOD shows little changes over land and ocean in the past three decades, because opposite trends in different regions cancel each other in the global average. This highlights the need for regional-scale aerosol assessment, as the global average value conceals regional changes, and thus is not sufficient for assessing changes in aerosol loading.

scholarly journals Simulations of column-average CO<sub>2</sub> and CH<sub>4</sub> using the NIES TM with a hybrid sigma-isentropic (σ−θ) vertical coordinate

2012 ◽  
Vol 12 (3) ◽  
pp. 8053-8106 ◽  
Author(s):  
D. A. Belikov ◽  
S. Maksyutov ◽  
V. Sherlock ◽  
S. Aoki ◽  
N. M. Deutscher ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Model Performance ◽  
Vertical Motion ◽  
West Siberia ◽  
Total Carbon ◽  
Tracer Transport ◽  
Chemical Transport Model ◽  
Near Surface ◽  
Vertical Coordinate

Abstract. We have developed an improved version of the National Institute for Environmental Studies (NIES) three-dimensional chemical transport model (TM) designed for accurate tracer transport simulations in the stratosphere, given the use of a hybrid sigma-isentropic (σ−θ) vertical coordinate that employs both terrain following and isentropic parts switched smoothly around the tropopause. The air-ascending rate was derived from the effective heating rate and was used to simulate vertical motion in the isentropic part of the grid (above level 350 K), which was adjusted to fit to the observed age of the air in the stratosphere. Multi-annual simulations were conducted using NIES TM to evaluate vertical profiles and dry-air column-averaged mole fractions of CO2 and CH4. Comparisons with balloon-borne observations over Sanriku (Japan) in 2000–2007 revealed that the tracer transport simulations in the upper troposphere and lower stratosphere are performed with accuracies of ~5% for CH4 and SF6, and ~1% for CO2 compared with the observed volume-mixing ratios. The simulated XCO2 and XCH4 were evaluated against daily ground-based high-resolution Fourier Transform Spectrometer (FTS) observations measured at twelve sites of the Total Carbon Column Observing Network (TCCON) (Bialystok, Bremen, Darwin, Garmisch, Izaña, Lamont, Lauder, Orleans, Park Falls, Sodankylä, Tsukuba, and Wollongong) between January 2009 and January 2011. The comparison shows the model's ability to reproduce the site-dependent seasonal cycles as observed by TCCON, with correlation coefficients typically on the order 0.8–0.9 and 0.4–0.8 for XCO2 and XCH4, respectively, and mean model biases of ±0.2% and ±0.5%, excluding Sodankylä, where strong biases are found. The capturing of tracer total column mole fractions is strongly dependent on the model's ability to reproduce seasonal variations in tracer concentrations in the planetary boundary layer (PBL). We found a marked difference in the model's ability to reproduce near-surface concentrations at sites located some distance from multiple emission sources and where high emissions play a notable role in the tracer's budget. Comparisons with aircraft observations over Surgut (West Siberia), in an area with high emissions of methane from wetlands, show contrasting model performance in the PBL and in the free troposphere. This is another instance where the representation of the PBL is critical in simulating the tracer total columns.

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