Global Indirect Radiative Forcing Caused by Aerosols

2009 ◽  
pp. 451-468 ◽  
Author(s):  
Jim Haywood ◽  
Leo Donner ◽  
Andy Jones ◽  
Jean-Christophe Golaz
Keyword(s):  
Radiative Forcing ◽  
Indirect Radiative Forcing

scholarly journals Global source attribution of sulfate concentration and direct and indirect radiative forcing

2017 ◽  
Vol 17 (14) ◽  
pp. 8903-8922 ◽  
Author(s):  
Yang Yang ◽  
Hailong Wang ◽  
Steven J. Smith ◽  
Richard Easter ◽  
Po-Lun Ma ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Dimethyl Sulfide ◽  
Sulfur Source ◽  
Atmospheric Conditions ◽  
So2 Emissions ◽  
Near Surface ◽  
Indirect Radiative Forcing ◽  
Global Source

Abstract. The global source–receptor relationships of sulfate concentrations, and direct and indirect radiative forcing (DRF and IRF) from 16 regions/sectors for years 2010–2014 are examined in this study through utilizing a sulfur source-tagging capability implemented in the Community Earth System Model (CESM) with winds nudged to reanalysis data. Sulfate concentrations are mostly contributed by local emissions in regions with high emissions, while over regions with relatively low SO2 emissions, the near-surface sulfate concentrations are primarily attributed to non-local sources from long-range transport. Regional source efficiencies of sulfate concentrations are higher over regions with dry atmospheric conditions and less export, suggesting that lifetime of aerosols, together with regional export, is important in determining regional air quality. The simulated global total sulfate DRF is −0.42 W m−2, with −0.31 W m−2 contributed by anthropogenic sulfate and −0.11 W m−2 contributed by natural sulfate, relative to a state with no sulfur emissions. In the Southern Hemisphere tropics, dimethyl sulfide (DMS) contributes 17–84 % to the total DRF. East Asia has the largest contribution of 20–30 % over the Northern Hemisphere mid- and high latitudes. A 20 % perturbation of sulfate and its precursor emissions gives a sulfate incremental IRF of −0.44 W m−2. DMS has the largest contribution, explaining −0.23 W m−2 of the global sulfate incremental IRF. Incremental IRF over regions in the Southern Hemisphere with low background aerosols is more sensitive to emission perturbation than that over the polluted Northern Hemisphere.

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 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 Uncertainty analysis of indirect radiative forcing by anthropogenic sulfate aerosols

1998 ◽  
Vol 103 (D4) ◽  
pp. 3815-3823 ◽  
Author(s):  
Wenwei Pan ◽  
Menner A. Tatang ◽  
Gregory J. McRae ◽  
Ronald G. Prinn
Keyword(s):  
Uncertainty Analysis ◽  
Radiative Forcing ◽  
Sulfate Aerosols ◽  
Indirect Radiative Forcing

scholarly journals Indirect radiative forcing by ion-mediated nucleation of aerosol

2012 ◽  
Vol 12 (23) ◽  
pp. 11451-11463 ◽  
Author(s):  
F. Yu ◽  
G. Luo ◽  
X. Liu ◽  
R. C. Easter ◽  
X. Ma ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Spatial Variations ◽  
Climate Feedback ◽  
Formation Mechanisms ◽  
Clear Understanding ◽  
Liquid Water Path ◽  
Cloud Forcing ◽  
Indirect Radiative Forcing

Abstract. A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN) in generating new particles and cloud condensation nuclei (CCN) in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5). Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN), the presence of ionization (i.e., IMN) halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation) to 65% (at 1.0% supersaturation), and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF) by 3.67 W m−2 (more negative) and longwave cloud forcing by 1.78 W m−2 (more positive), with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2) is a factor of ~3 higher that of a previous study (1.15 W m−2) based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (~−0.02 W m−2) but have larger inter-annual (from −0.18 to 0.17 W m−2) and spatial variations.

scholarly journals The effect of ENSO-induced rainfall and circulation changes on the direct and indirect radiative forcing from Indonesian biomass-burning aerosols

2012 ◽  
Vol 12 (23) ◽  
pp. 11395-11416 ◽  
Author(s):  
A. Chrastansky ◽  
L. D. Rotstayn
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Radiative Forcing ◽  
El Nino ◽  
La Niña ◽  
Aerosol Forcing ◽  
La Nina ◽  
Rainfall Anomalies ◽  
Aerosol Emissions ◽  
Indirect Radiative Forcing

Abstract. Emissions of biomass-burning aerosols from the Indonesian region are known to vary in response to rainfall anomalies associated with the El Niño Southern Oscillation (ENSO). For the severe El Niño-related drought in 1997, there have been several attempts to estimate the direct radiative forcing from increased aerosol emissions over Indonesia, as well as the associated feedbacks on climate. However, these estimates have not considered indirect aerosol effects. Another question that has not been addressed is whether the effect of ENSO-related circulation and rainfall anomalies on radiative forcing is significant relative to the effect of changes in emissions. In this study, we analyse the direct and first indirect radiative forcing from El Niño-related increased emissions of Indonesian biomass-burning aerosols, with and without the influence of ENSO-related rainfall and circulation anomalies. We compare two experiments that are performed with the CSIRO-Mk3.6 atmospheric global climate model (GCM). The first experiment (AMIP) consists of a pair of runs that respectively represent El Niño and La Niña conditions. In these runs, the distribution of aerosols is simulated under the influence of realistic Indonesian biomass-burning aerosol emissions and sea surface temperatures (SSTs) for 1997 (El Niño) and 2000 (La Niña). The second experiment (CLIM) is identical to AMIP, but is forced by climatological SSTs, so that in CLIM meteorological differences between 1997 and 2000 are suppressed. The comparison of AMIP and CLIM shows that the aerosol radiative forcing anomalies associated with ENSO (El Niño minus La Niña) are substantially stronger when ENSO-related SST anomalies are taken into account. For the first indirect effect, the influence of SST-induced changes in rainfall and circulation exceeds that of changes in emissions. For the direct aerosol forcing, the influence of changes in SSTs and emissions are of comparable magnitude. Averaged over the Indonesian region (5.6° N–11.2° S, 96.6° E–150.9° E), the first indirect forcing is −0.7 Wm−2 in CLIM and −2.2 Wm−2 in AMIP during the months July to November. The direct aerosol forcing at the top of the atmosphere (surface) is −1.0 (−5.3) Wm−2 in CLIM and −1.8 (−9.1) Wm−2 in AMIP during the same period. Our results suggest that (a) the indirect aerosol effect from biomass-burning aerosols is strong enough to play an important role for impact assessments, and (b) that impacts of biomass-burning aerosols would be considerably underestimated if feedbacks of ENSO-related SST variations on radiative forcing are not taken into account.

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 Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

2012 ◽  
Vol 12 (3) ◽  
pp. 8009-8051 ◽  
Author(s):  
A. Schmidt ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
A. Rap ◽  
K. J. Pringle ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Cloud Droplet ◽  
Volcanic Emissions ◽  
Large Uncertainty ◽  
Volcanic Degassing ◽  
Uncertainty Range ◽  
Cloud Albedo ◽  
Albedo Effect ◽  
The Impact ◽  
Indirect Radiative Forcing

Abstract. Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. Here, we use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of −1.06 W m−2 in the PI era but only −0.56 W m−2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a −50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between −1.16 W m−2 and −0.86 W m−2. Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate.

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