scholarly journals Radiative forcing estimates of sulfate aerosol in coupled climate-chemistry models with emphasis on the role of the temporal variability

2012 ◽  
Vol 12 (12) ◽  
pp. 5583-5602 ◽  
Author(s):  
C. Déandreis ◽  
Y. Balkanski ◽  
J. L. Dufresne ◽  
A. Cozic
Keyword(s):  
Temporal Variability ◽  
Radiative Forcing ◽  
Climate Model ◽  
Circulation Model ◽  
Reference Method ◽  
Sulfate Aerosol ◽  
The Impact ◽  
Net Fluxes ◽  
Indirect Radiative Forcing ◽  
Aerosol Radiative

Abstract. This paper describes the impact on the sulfate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulfate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for the direct and first indirect effects of sulfate. The direct effect respond almost linearly to rapid changes in concentrations whereas the first indirect effect shows a strong non-linearity. In particular, sulfate temporal variability causes a modification of the short wave net fluxes at the top of the atmosphere of +0.24 and +0.22 W m−2 for the present and preindustrial periods, respectively. This change is small compared to the value of the net flux at the top of the atmosphere (about 240 W m−2). The effect is more important in regions with low-level clouds and intermediate sulfate aerosol concentrations (from 0.1 to 0.8 μg (SO4) m−3 in our model). The computation of the aerosol direct radiative forcing is quite straightforward and the temporal variability has little effect on its mean value. In contrast, quantifying the first indirect radiative forcing requires tackling technical issues first. We show that the preindustrial sulfate concentrations have to be calculated with the same meteorological trajectory used for computing the present ones. If this condition is not satisfied, it introduces an error on the estimation of the first indirect radiative forcing. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8% in the first indirect radiative forcing. This change reaches 50% in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing.

scholarly journals Radiative forcing estimates in coupled climate-chemistry models with emphasis on the role of the temporal variability

2011 ◽  
Vol 11 (8) ◽  
pp. 24313-24364 ◽  
Author(s):  
C. Déandreis ◽  
Y. Balkanski ◽  
J. L. Dufresne ◽  
A. Cozic
Keyword(s):  
Temporal Variability ◽  
Radiative Forcing ◽  
Climate Model ◽  
Circulation Model ◽  
Reference Method ◽  
Sulphate Aerosol ◽  
The Impact ◽  
Net Fluxes ◽  
Indirect Radiative Forcing ◽  
Aerosol Radiative

Abstract. This paper describes the impact on the sulphate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulphate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for direct and first indirect effects of sulphate. The direct effect responds almost linearly to rapid changes in concentrations whereas, the first indirect effect shows a strong non-linearity. In particular, sulphate temporal variability causes a large modification of the short wave net fluxes at the top of the atmosphere (+0.24 and +0.22 W m−2 for respectively, the present and preindustrial periods that are about 30 % of the total radiative forcing of sulfate). The effect is particularly important in regions with low-level clouds and intermediate sulphate aerosol concentrations (from 0.1 to 0.8 μg (SO4) m−3 in our model). If computation of the aerosol direct radiative forcing is quite straightforward and has few effects; quantifying the first indirect radiative forcing requires first to tackle technical issues. We show that preindustrial sulphate concentrations have to be calculated with the same meteorological trajectory than that used for computing present ones. If this condition is not satisfied, the error on the estimation of the first indirect radiative forcing is of 60 %. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8 % in the first indirect radiative forcing. This change reaches 50 % in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing.

scholarly journals Modelled and observed changes in aerosols and surface solar radiation over Europe between 1960 and 2009

2015 ◽  
Vol 15 (16) ◽  
pp. 9477-9500 ◽  
Author(s):  
S. T. Turnock ◽  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
M. T. Woodhouse ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Radiative Forcing ◽  
Climate Model ◽  
Suspended Particle ◽  
Sulfate Aerosol ◽  
Anthropogenic Aerosols ◽  
Surface Solar Radiation ◽  
Aerosol Mass ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Substantial changes in anthropogenic aerosols and precursor gas emissions have occurred over recent decades due to the implementation of air pollution control legislation and economic growth. The response of atmospheric aerosols to these changes and the impact on climate are poorly constrained, particularly in studies using detailed aerosol chemistry–climate models. Here we compare the HadGEM3-UKCA (Hadley Centre Global Environment Model-United Kingdom Chemistry and Aerosols) coupled chemistry–climate model for the period 1960–2009 against extensive ground-based observations of sulfate aerosol mass (1978–2009), total suspended particle matter (SPM, 1978–1998), PM10 (1997–2009), aerosol optical depth (AOD, 2000–2009), aerosol size distributions (2008–2009) and surface solar radiation (SSR, 1960–2009) over Europe. The model underestimates observed sulfate aerosol mass (normalised mean bias factor (NMBF) = −0.4), SPM (NMBF = −0.9), PM10 (NMBF = −0.2), aerosol number concentrations (N30 NMBF = −0.85; N50 NMBF = −0.65; and N100 NMBF = −0.96) and AOD (NMBF = −0.01) but slightly overpredicts SSR (NMBF = 0.02). Trends in aerosol over the observational period are well simulated by the model, with observed (simulated) changes in sulfate of −68 % (−78 %), SPM of −42 % (−20 %), PM10 of −9 % (−8 %) and AOD of −11 % (−14 %). Discrepancies in the magnitude of simulated aerosol mass do not affect the ability of the model to reproduce the observed SSR trends. The positive change in observed European SSR (5 %) during 1990–2009 ("brightening") is better reproduced by the model when aerosol radiative effects (ARE) are included (3 %), compared to simulations where ARE are excluded (0.2 %). The simulated top-of-the-atmosphere aerosol radiative forcing over Europe under all-sky conditions increased by > 3.0 W m−2 during the period 1970–2009 in response to changes in anthropogenic emissions and aerosol concentrations.

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 Modelled and observed changes in aerosols and surface solar radiation over Europe between 1960 and 2009

2015 ◽  
Vol 15 (9) ◽  
pp. 13457-13513 ◽  
Author(s):  
S. T. Turnock ◽  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
M. T. Woodhouse ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Sulfate Aerosol ◽  
Anthropogenic Aerosols ◽  
Surface Solar Radiation ◽  
Aerosol Mass ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Substantial changes in anthropogenic aerosols and precursor gas emissions have occurred over recent decades due to the implementation of air pollution control legislation and economic growth. The response of atmospheric aerosols to these changes and the impact on climate are poorly constrained, particularly in studies using detailed aerosol chemistry climate models. Here we compare the HadGEM3-UKCA coupled chemistry-climate model for the period 1960 to 2009 against extensive ground based observations of sulfate aerosol mass (1978–2009), total suspended particle matter (SPM, 1978–1998), PM10 (1997–2009), aerosol optical depth (AOD, 2000–2009) and surface solar radiation (SSR, 1960–2009) over Europe. The model underestimates observed sulfate aerosol mass (normalised mean bias factor (NMBF) = −0.4), SPM (NMBF = −0.9), PM10 (NMBF = −0.2) and aerosol optical depth (AOD, NMBF = −0.01) but slightly overpredicts SSR (NMBF = 0.02). Trends in aerosol over the observational period are well simulated by the model, with observed (simulated) changes in sulfate of −68% (−78%), SPM of −42% (−20%), PM10 of −9% (−8%) and AOD of −11% (−14%). Discrepancies in the magnitude of simulated aerosol mass do not affect the ability of the model to reproduce the observed SSR trends. The positive change in observed European SSR (5%) during 1990–2009 ("brightening") is better reproduced by the model when aerosol radiative effects (ARE) are included (3%), compared to simulations where ARE are excluded (0.2%). The simulated top-of-the-atmosphere aerosol radiative forcing over Europe under all-sky conditions increased by 3 W m−2 during the period 1970–2009 in response to changes in anthropogenic emissions and aerosol concentrations.

scholarly journals A global modeling study on carbonaceous aerosol microphysical characteristics and radiative forcing

2010 ◽  
Vol 10 (2) ◽  
pp. 4543-4592 ◽  
Author(s):  
S. E. Bauer ◽  
S. Menon ◽  
D. Koch ◽  
T. C. Bond ◽  
K. Tsigaridis
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Model ◽  
Carbonaceous Aerosol ◽  
Complex Nature ◽  
Carbonaceous Particle ◽  
Aerosol Radiative Forcing ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, cloud-indirect and semi-direct forcing effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative forcing. Our best estimate for net direct and indirect aerosol radiative forcing between 1750 and 2000 is −0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative forcing can vary between −0.32 to −0.75 W/m2 depending on these carbonaceous particle properties at emission. Assuming that sulfates, nitrates and secondary organics form a coating around a black carbon core, rather than forming a uniformly mixed particle, changes the overall net aerosol radiative forcing from negative to positive. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Black carbon absorption is amplified by sulfate and nitrate coatings, but even more strongly by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative forcing when sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to climate benefits.

scholarly journals The Impact of Changes in Cloud Water pH on Aerosol Radiative Forcing

2019 ◽  
Vol 46 (7) ◽  
pp. 4039-4048 ◽  
Author(s):  
S. T. Turnock ◽  
G. W. Mann ◽  
M. T. Woodhouse ◽  
M. Dalvi ◽  
F. M. O'Connor ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Water ◽  
Aerosol Radiative Forcing ◽  
Water Ph ◽  
The Impact ◽  
Aerosol Radiative

scholarly journals Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

2011 ◽  
Vol 11 (10) ◽  
pp. 5045-5077 ◽  
Author(s):  
K. Semeniuk ◽  
V. I. Fomichev ◽  
J. C. McConnell ◽  
C. Fu ◽  
S. M. L. Melo ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Radiative Forcing ◽  
Climate Model ◽  
Middle Atmosphere ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Particle Precipitation ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
The Impact

Abstract. The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton events and galactic cosmic rays on the middle atmosphere is examined using a chemistry climate model. This process study uses ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10 % in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4 % more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

scholarly journals Sensitivity of aerosol radiative effects to different mixing assumptions in the AEROPT 1.0 submodel of the EMAC atmospheric-chemistry–climate model

2014 ◽  
Vol 7 (5) ◽  
pp. 2503-2516 ◽  
Author(s):  
K. Klingmüller ◽  
B. Steil ◽  
C. Brühl ◽  
H. Tost ◽  
J. Lelieveld
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
Black Carbon ◽  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Climate Model ◽  
Mixing Rule ◽  
Aerosol Optical Properties ◽  
Internal Mixing ◽  
Aerosol Radiative

Abstract. The modelling of aerosol radiative forcing is a major cause of uncertainty in the assessment of global and regional atmospheric energy budgets and climate change. One reason is the strong dependence of the aerosol optical properties on the mixing state of aerosol components, such as absorbing black carbon and, predominantly scattering sulfates. Using a new column version of the aerosol optical properties and radiative-transfer code of the ECHAM/MESSy atmospheric-chemistry–climate model (EMAC), we study the radiative transfer applying various mixing states. The aerosol optics code builds on the AEROPT (AERosol OPTical properties) submodel, which assumes homogeneous internal mixing utilising the volume average refractive index mixing rule. We have extended the submodel to additionally account for external mixing, partial external mixing and multilayered particles. Furthermore, we have implemented the volume average dielectric constant and Maxwell Garnett mixing rule. We performed regional case studies considering columns over China, India and Africa, corroborating much stronger absorption by internal than external mixtures. Well-mixed aerosol is a good approximation for particles with a black-carbon core, whereas particles with black carbon at the surface absorb significantly less. Based on a model simulation for the year 2005, we calculate that the global aerosol direct radiative forcing for homogeneous internal mixing differs from that for external mixing by about 0.5 W m−2.

Sign in / Sign up

Export Citation Format

Share Document