scholarly journals Anthropogenic influence on SOA and the resulting radiative forcing

2009 ◽  
Vol 9 (8) ◽  
pp. 2715-2728 ◽  
Author(s):  
C. R. Hoyle ◽  
G. Myhre ◽  
T. K. Berntsen ◽  
I. S. A. Isaksen
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Organic Aerosols ◽  
Aerosol Chemistry ◽  
Sulphate Aerosol ◽  
Chemistry Transport Model ◽  
Sulphate Aerosols ◽  
Ipcc Report ◽  
The Difference ◽  
Different Sources

Abstract. The effect of chemical changes in the atmosphere since the pre-industrial period on the distributions and burdens of Secondary Organic Aerosol (SOA) has been calculated using the off-line aerosol chemistry transport model Oslo CTM2. The production of SOA was found to have increased from about 35 Tg yr−1 to 53 Tg yr−1 since pre-industrial times, leading to an increase in the global annual mean SOA burden from 0.33 Tg to 0.50 Tg, or about 51%. The effect of allowing semi-volatile species to partition to sulphate aerosol was also tested, leading to an increase in SOA production from about 43 Tg yr−1 to 69 Tg yr−1 since pre-industrial times, while the annual mean SOA burden increased from 0.44 Tg to 0.70 Tg, or about 59%. The increases were greatest over industrialised areas, especially when partitioning to sulphate aerosol was allowed, as well as over regions with high biogenic precursor emissions. The contribution of emissions from different sources to the larger SOA burdens has been calculated. The results suggest that the majority of the increase was caused by emissions of primary organic aerosols (POA), from fossil fuel and bio fuel combustion. As yet, very few radiative forcing estimates of SOA exist, and no such estimates were provided in the latest IPCC report. In this study, we found that the change in SOA burden caused a radiative forcing (defined here as the difference between the pre-industrial and the present day run) of −0.09 W m−2, when SOA was allowed to partition to both organic and sulphate aerosols, and −0.06 W m−2 when only partitioning to organic aerosols was assumed. Therefore, the radiative forcing of SOA was found to be stronger than the best estimate for POA in the latest IPCC assessment.

scholarly journals Anthropogenic influence on SOA and the resulting radiative forcing

2008 ◽  
Vol 8 (6) ◽  
pp. 18911-18936 ◽  
Author(s):  
C. R. Hoyle ◽  
G. Myhre ◽  
T. K. Berntsen ◽  
I. S. A. Isaksen
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Aerosol Chemistry ◽  
Chemistry Transport Model ◽  
Sulphate Aerosols ◽  
Ipcc Report ◽  
Production Increase ◽  
Different Sources

Abstract. The pre-industrial and present day distributions and burdens of Secondary Organic Aerosol (SOA) have been calculated using the off-line aerosol chemistry transport model Oslo CTM2. The production of SOA was found to have increased from about 43 Tg yr−1 to 69 Tg yr−1 since pre-industrial times, leading to an increase in the global annual mean SOA burden from 0.44 Tg to 0.70 Tg, or about 59%. The increases are greatest over industrialised areas, as well as over regions with high biogenic precursor emissions. The contribution of emissions from different sources to the larger SOA burdens has been calculated. The results suggest that the majority of the increase is caused by emissions of primary organic aerosols (POA), from fossil fuel and bio fuel combustion. When SOA partitioning to ammonium sulphate aerosol was not accounted for, the increase in SOA burden between pre-industrial times and the present was found to be lower (51%), with a production increase of 55%. As yet, very few radiative forcing estimates of SOA exist, and no such estimates were provided in the latest IPCC report. In this study, we find that the change in SOA burden caused a radiative forcing of −0.09 W m−2, when SOA was allowed to partition to both organic and sulphate aerosols, and −0.06 W m−2 when only partitioning to organic aerosols was assumed. Therefore, the radiative forcing of SOA is found to be substantially stronger than the best estimate for POA in the latest IPCC assessment.

scholarly journals An alternative way to evaluate chemistry-transport model variability

2017 ◽  
Vol 10 (3) ◽  
pp. 1199-1208 ◽  
Author(s):  
Laurent Menut ◽  
Sylvain Mailler ◽  
Bertrand Bessagnet ◽  
Guillaume Siour ◽  
Augustin Colette ◽  
...  
Keyword(s):  
Transport Model ◽  
Model Performance ◽  
Error Statistics ◽  
Chemistry Transport Model ◽  
Temporal Correlations ◽  
Time Period ◽  
The Difference ◽  
Model Variability ◽  
Spatial Locations ◽  
Statistical Indicators

Abstract. A simple and complementary model evaluation technique for regional chemistry transport is discussed. The methodology is based on the concept that we can learn about model performance by comparing the simulation results with observational data available for time periods other than the period originally targeted. First, the statistical indicators selected in this study (spatial and temporal correlations) are computed for a given time period, using colocated observation and simulation data in time and space. Second, the same indicators are used to calculate scores for several other years while conserving the spatial locations and Julian days of the year. The difference between the results provides useful insights on the model capability to reproduce the observed day-to-day and spatial variability. In order to synthesize the large amount of results, a new indicator is proposed, designed to compare several error statistics between all the years of validation and to quantify whether the period and area being studied were well captured by the model for the correct reasons.

scholarly journals DMS atmospheric concentrations and sulphate aerosol indirect radiative forcing: a sensitivity study to the DMS source representation and oxidation

2003 ◽  
Vol 3 (1) ◽  
pp. 49-65 ◽  
Author(s):  
O. Boucher ◽  
C. Moulin ◽  
S. Belviso ◽  
O. Aumont ◽  
L. Bopp ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
General Circulation ◽  
Marine Boundary Layer ◽  
Circulation Model ◽  
Sensitivity Study ◽  
Sulphate Aerosol ◽  
Sulphate Aerosols ◽  
The Impact ◽  
Atmospheric Concentrations ◽  
Indirect Radiative Forcing

Abstract. The global sulphur cycle has been simulated using a general circulation model with a focus on the source and oxidation of atmospheric dimethylsulphide (DMS). The sensitivity of atmospheric DMS to the oceanic DMS climatology, the parameterisation of the sea-air transfer and to the oxidant fields have been studied. The importance of additional oxidation pathways (by O3 in the gas- and aqueous-phases and by BrO in the gas phase) not incorporated in global models has also been evaluated. While three different climatologies of the oceanic DMS concentration produce rather similar global DMS fluxes to the atmosphere at 24-27 Tg S yr -1, there are large differences in the spatial and seasonal distribution. The relative contributions of OH and NO3 radicals to DMS oxidation depends critically on which oxidant fields are prescribed in the model. Oxidation by O3 appears to be significant at high latitudes in both hemispheres. Oxidation by BrO could be significant even for BrO concentrations at sub-pptv levels in the marine boundary layer. The impact of such refinements on the DMS chemistry onto the indirect radiative forcing by anthropogenic sulphate aerosols is also discussed.

scholarly journals Equilibrium of sinks and sources of sulphate over Europe: comparison between a six-year simulation and EMEP observations

2009 ◽  
Vol 9 (13) ◽  
pp. 4505-4519 ◽  
Author(s):  
M. Ménégoz ◽  
D. Salas y Melia ◽  
M. Legrand ◽  
H. Teyssèdre ◽  
M. Michou ◽  
...  
Keyword(s):  
Transport Model ◽  
Weather Conditions ◽  
General Tendency ◽  
Chemistry Transport Model ◽  
Annual Variations ◽  
Sulphur Cycle ◽  
Sulphate Aerosols ◽  
Chemical Scheme ◽  
One Year ◽  
Year 2000

Abstract. Sulphate distributions were simulated with a global chemistry transport model. A chemical scheme describing the sulphur cycle and the parameterisations of the main sinks for sulphate aerosols were included in the model. A six-year simulation was conducted from the years 2000 to 2005, driven by the ECMWF operational analyses. Emissions come from an inventory representative of the year 2000. This paper focuses on the analysis of the sulphate sinks and sources over Europe for the entire period of simulation. The Sulphate burden shows a marked annual cycle, which is the result of the annual variations of the aqueous and gaseous chemistry. Regionally, the monthly mean aerosol burden can vary by a factor of 2 from one year to another, because of different weather conditions, driving chemistry, transport and wet deposition of sulphate aerosols. Sulphate ground concentrations, scavenging fluxes and precipitation modelled were compared with observations. The model represents quite well sulphate fields over Europe, but has a general tendency to overestimate sulphate ground concentrations, in particular over Northern Europe. We assume that it is linked to the representation of the scavenging fluxes, which are underestimated. We suggest that uncertainties in modelled precipitation explain only partially the underestimation of the scavenging fluxes in the model.

Air pollution and cloud-interaction over Europe in 1985 and today

2020 ◽  
Author(s):  
Roland Schrödner ◽  
Christa Genz ◽  
Bernd Heinold ◽  
Holger Baars ◽  
Silvia Henning ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Cloud Droplet ◽  
Forecast Model ◽  
Sensitivity Study ◽  
High Definition ◽  
Chemistry Transport Model ◽  
Meteorological Model ◽  
Cloud Properties ◽  
Aerosol Mass

<p>Aerosol concentrations over Europe and Germany were simulated for the years 1985 and 2013 using the aerosol-chemistry transport model COSMO-MUSCAT. The aerosol fields from the two simulations were used in a high-resolution meteorological model for a sensitivity study on cloud properties. The modelled aerosol and cloud variables were compared to a variety of available observations, including satellites, remote sensing and in-situ observations. Finally, the radiative forcing of the aerosol could be estimated from the different sensitivity simulations.</p><p>Due to reduction of emissions the ambient aerosol mass and number in Europe was strongly decreased since the 1980s. Hence, today’s number of particles in the CCN size range is smaller. The HD(CP)<sup>2</sup> (High Definition Clouds and Precipitation for Climate Prediction) project amongst others aimed at analysing the effect of the emission reduction on cloud properties.</p><p>As a pre-requiste, the aerosol mass, number, and composition over Germany were simulated for 1985 and 2013 using the regional chemistry-transport-model COSMO-MUSCAT. The EDGAR emission inventory was used for both years.</p><p>The model results were compared to observations from the two HD(CP)<sup>2</sup> campaigns that took place in 2013 (HOPE, HOPE-Melpitz) as well as the AVHRR aerosol optical thickness product, which is available from 1981 onwards. Despite the fact, that emissions of the 1980s are very uncertain, the modelled AOD is in good agreement with observations. The modelled mean CCN number concentration in 1985 is a factor of 2-4 higher than in 2013.</p><p>Within HD(CP)<sup>2</sup>, the ICON weather forecast model was applied in a configuration allowing for large-eddy simulations. In these simulations, the time-varying CCN fields for the year 1985 and 2013 calculated with COSMO-MUSCAT were used as input for ICON-LEM. In the present-day simulation, the cloud droplet number agrees with observations, whereas the perturbed (1985) simulation does not with droplet numbers about twice as high as in 2013. Also, for other cloud variables systematic changes between the two scenarios were observed.</p>

scholarly journals Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

2017 ◽  
Vol 17 (23) ◽  
pp. 14333-14352 ◽  
Author(s):  
Ben Newsome ◽  
Mat Evans
Keyword(s):  
Rate Constant ◽  
Atmospheric Chemistry ◽  
Rate Constants ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Transport Model ◽  
Surface Ozone ◽  
Chemistry Transport Model ◽  
The Impact ◽  
Chemical Rate

Abstract. Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global, use these rate constants. Expert panels evaluate laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the Jet Propulsion Laboratory (JPL) and International Union of Pure and Applied Chemistry (IUPAC) evaluations we assess the influence of 50 mainly inorganic rate constants and 10 photolysis rates on tropospheric composition through the use of the GEOS-Chem chemistry transport model. We assess the impact on four standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH →M  HNO3 and O3 + NO  →  NO2 + O2 are the two largest sources of uncertainty in these metrics. The absolute magnitude of the change in the metrics is similar if rate constants are increased or decreased by their σ values. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 10, 11, 16 and 16 %, respectively. These are larger than the spread between models in recent model intercomparisons. Remote regions such as the tropics, poles and upper troposphere are most uncertain. This chemical uncertainty is sufficiently large to suggest that rate constant uncertainty should be considered alongside other processes when model results disagree with measurement. Calculations for the pre-industrial simulation allow a tropospheric ozone radiative forcing to be calculated of 0.412 ± 0.062 W m−2. This uncertainty (13 %) is comparable to the inter-model spread in ozone radiative forcing found in previous model–model intercomparison studies where the rate constants used in the models are all identical or very similar. Thus, the uncertainty of tropospheric ozone radiative forcing should expanded to include this additional source of uncertainty. These rate constant uncertainties are significant and suggest that refinement of supposedly well-known chemical rate constants should be considered alongside other improvements to enhance our understanding of atmospheric processes.

scholarly journals A quasi chemistry-transport model mode for EMAC

2011 ◽  
Vol 4 (1) ◽  
pp. 195-206 ◽  
Author(s):  
R. Deckert ◽  
P. Jöckel ◽  
V. Grewe ◽  
K.-D. Gottschaldt ◽  
P. Hoor
Keyword(s):  
Water Vapor ◽  
Nitric Acid ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Climate Simulation ◽  
Chemistry Transport Model ◽  
Mixing Ratios ◽  
Reference Simulation ◽  
The Difference ◽  
Chemical Water

Abstract. A quasi chemistry-transport model mode (QCTM) is presented for the numerical chemistry-climate simulation system ECHAM/MESSy Atmospheric Chemistry (EMAC). It allows for a quantification of chemical signals through suppression of any feedback between chemistry and dynamics. Noise would otherwise interfere too strongly. The signal is calculated from the difference of two QCTM simulations, a reference simulation and a sensitivity simulation. In order to avoid the feedbacks, the simulations adopt the following offline chemical fields: (a) offline mixing ratios of radiatively active substances enter the radiation scheme, (b) offline mixing ratios of nitric acid enter the scheme for re-partitioning and sedimentation from polar stratospheric clouds, (c) and offline methane oxidation is the exclusive source of chemical water-vapor tendencies. Any set of offline fields suffices to suppress the feedbacks, though may be inconsistent with the simulation setup. An adequate set of offline climatologies can be produced from a non-QCTM simulation using the setup of the reference simulation. Test simulations reveal the particular importance of adequate offline fields associated with (a). Inconsistencies from (b) are negligible when using adequate fields of nitric acid. Acceptably small inconsistencies come from (c), but should vanish for an adequate prescription of chemical water vapor tendencies. Toggling between QCTM and non-QCTM is done via namelist switches and does not require a source code re-compilation.

scholarly journals Stratospheric age of air computed with trajectories based on various 3D-Var and 4D-Var data sets

2005 ◽  
Vol 5 (1) ◽  
pp. 1-7 ◽  
Author(s):  
M. P. Scheele ◽  
P. C. Siegmund ◽  
P. F. J. Velthoven
Keyword(s):  
Time Series ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Segment Length ◽  
Data Sets ◽  
Wind Fields ◽  
Chemistry Transport Model ◽  
Backward Trajectories ◽  
Forecast Data ◽  
The Difference

Abstract. The age of stratospheric air is computed with a trajectory model, using ECMWF ERA-40 3D-Var and operational 4D-Var winds. Analysis as well as forecast data are used. In the latter case successive forecast segments are put together to get a time series of the wind fields. This is done for different forecast segment lengths. The sensitivity of the computed age to the forecast segment length and assimilation method are studied, and the results are compared with observations and with results from a chemistry transport model that uses the same data sets. A large number of backward trajectories are started in the stratosphere, and from the fraction of these trajectories that has passed the tropopause the age of air is computed. First, for ten different data sets 50-day backward trajectories starting in the tropical lower stratosphere are computed. The results show that in this region the computed cross-tropopause transport decreases with increasing forecast segment length. Next, for three selected data sets (3D-Var 24-h and 4D-Var 72-h forecast segments, and 4D-Var analyses) 5-year backward trajectories are computed that start all over the globe at an altitude of 20km. For all data sets the computed ages of air in the extratropics are smaller than the observation-based age. For 4D-Var forecast series they are closest to the observation-based values, but still 0.5-1.5 year too small. Compared to the difference in age between the results for the different data sets, the difference in age between the trajectory and the chemistry transport model results is small.

scholarly journals The HNO<sub>3</sub> forming branch of the HO<sub>2</sub> + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings

2011 ◽  
Vol 11 (5) ◽  
pp. 14801-14835 ◽  
Author(s):  
O. A. Søvde ◽  
C. R. Hoyle ◽  
G. Myhre ◽  
I. S. A. Isaksen
Keyword(s):  
Radiative Forcing ◽  
Transport Model ◽  
Three Dimensional ◽  
Branching Ratio ◽  
Pressure Effects ◽  
Atmospheric Composition ◽  
Chemistry Transport Model ◽  
Radiative Forcings ◽  
Atmospheric Species ◽  
Temperature And Pressure Effects

Abstract. Recent laboratory measurements have shown the existence of a HNO3 forming branch of the HO2 + NO reaction. This reaction is the main source of atmospheric O3, through the subsequent photolysis of NO2, as well as being a major source of OH. The branching of the reaction to HNO3 reduces the formation of these species significantly, affecting O3 abundances, climate and the oxidation capacity of the troposphere. The Oslo CTM2, a three-dimensional chemistry transport model, is used to calculate atmospheric composition and trends with and without the new reaction branch. Results for the present day atmosphere, when both temperature and pressure effects on the branching ratio are accounted for, show an increase of the global, annual mean methane lifetime by 10.9 %, resulting from a 14.1 % reduction in the global, annual mean OH concentration. Comparisons with measurements show that including the new branch improves the modelled O3, but that it is not possible to conclude whether the NOy distribution improves. We model an approximately 11 % reduction in the tropical tropospheric O3 increase since pre-industrial times, as well as an 8 % decrease in the trend of OH concentration, when the new branch is accounted for. The radiative forcing due to changes in O3 over the industrial era was calculated as 0.33 W m−2, reducing to 0.26 W m−2 with the new reaction branch. These results are significant, and it is important that this reaction branching is confirmed by other laboratory groups.

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