scholarly journals Particulate absorption of solar radiation: anthropogenic aerosols vs. dust

2009 ◽  
Vol 9 (2) ◽  
pp. 6571-6595 ◽  
Author(s):  
C. Wang ◽  
G.-R. Jeong ◽  
N. Mahowald
Keyword(s):  
Solar Radiation ◽  
North Africa ◽  
Radiative Forcing ◽  
Indian Subcontinent ◽  
Critical Factor ◽  
Climate Impacts ◽  
Anthropogenic Aerosols ◽  
Solar Absorption ◽  
Boreal Spring ◽  
Dust Absorption

Abstract. Particulate solar absorption is a critical factor in determining the value and even sign of the direct radiative forcing of aerosols. The heating to the atmosphere and cooling to the Earth's surface caused by this absorption are hypothesized to have significant climate impacts. We find that anthropogenic aerosols play an important role around the globe in total particulate absorption of solar radiation. The global-average anthropogenic fraction in total aerosol absorbing optical depth exceeds 65% in all seasons. Combining the potentially highest dust absorption with the lowest anthropogenic absorption within our model range, this fraction would still exceed 47% in most seasons except for boreal spring (36%) when dust abundance reaches its peak. Nevertheless, dust aerosol is still a critical absorbing constituent over places including North Africa, the entire tropical Atlantic, and during boreal spring in most part of Eurasian continent. The equality in absorbing solar radiation of dust and anthropogenic aerosols appears to be particularly important over Indian subcontinent and nearby regions as well as North Africa.

scholarly journals Particulate absorption of solar radiation: anthropogenic aerosols vs. dust

2009 ◽  
Vol 9 (12) ◽  
pp. 3935-3945 ◽  
Author(s):  
C. Wang ◽  
G. R. Jeong ◽  
N. Mahowald
Keyword(s):  
Solar Radiation ◽  
North Africa ◽  
Radiative Forcing ◽  
Indian Subcontinent ◽  
Critical Factor ◽  
Climate Impacts ◽  
Anthropogenic Aerosols ◽  
Solar Absorption ◽  
Boreal Spring ◽  
Dust Absorption

Abstract. Particulate solar absorption is a critical factor in determining the value and even sign of the direct radiative forcing of aerosols. The heating to the atmosphere and cooling to the Earth's surface caused by this absorption are hypothesized to have significant climate impacts. We find that anthropogenic aerosols play an important role around the globe in total particulate absorption of solar radiation. The global-average anthropogenic fraction in total aerosol absorbing optical depth exceeds 65% in all seasons. Combining the potentially highest dust absorption with the lowest anthropogenic absorption within our model range, this fraction would still exceed 47% in most seasons except for boreal spring (36%) when dust abundance reaches its peak. Nevertheless, dust aerosol is still a critical absorbing constituent over places including North Africa, the entire tropical Atlantic, and during boreal spring in most part of Eurasian continent. The equality in absorbing solar radiation of dust and anthropogenic aerosols appears to be particularly important over Indian subcontinent and nearby regions as well as North Africa.

Climate forcing and committed global warming: GHGs, aerosols and ozone 1970-2010

2020 ◽  
Author(s):  
Alcide Zhao ◽  
David Stevenson ◽  
Massimi Bollasina
Keyword(s):  
Radiative Forcing ◽  
Daily Precipitation ◽  
Stratospheric Ozone ◽  
Temperature Response ◽  
Climate Impacts ◽  
Climate Projections ◽  
Anthropogenic Aerosols ◽  
Frequency Distributions ◽  
Climate Risks ◽  
Global Mean

<p>It is crucial to reduce uncertainties in our understanding of the climate impacts of short‐lived climate forcers, in the context that their emissions/concentrations are anticipated to decrease significantly in the coming decades worldwide. Using the Community Earth System Model (CESM1), we performed time‐slice experiments to investigate the effective radiative forcing (ERF) and climate respons to 1970–2010 changes in well‐mixed greenhouse gases (GHGs), anthropogenic aerosols, and tropospheric and stratospheric ozone. Once the present‐day climate has fully responded to 1970–2010 changes in all forcings, both the global mean temperature and precipitation responses are twice as large as the transient ones, with wet regions getting wetter and dry regions drier. The temperature response per unit ERF for short‐lived species varies considerably across many factors including forcing agents and the magnitudes and locations of emission changes. This suggests that the ERF should be used carefully to interpret the climate impacts of short‐lived climate forcers. Changes in both the mean and the probability distribution of global mean daily precipitation are driven mainly by GHG increases. However, changes in the frequency distributions of regional mean daily precipitation are more strongly influenced by changes in aerosols, rather than GHGs. This is particularly true over Asia and Europe where aerosol changes have significant impacts on the frequency of heavy‐to‐extreme precipitation. Our results may help guide more reliable near‐future climate projections and allow us to manage climate risks more effectively.</p>

scholarly journals Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy – Part 1: Intercomparison of modal and sectional aerosol modules

2022 ◽  
Vol 22 (1) ◽  
pp. 93-118
Author(s):  
Anton Laakso ◽  
Ulrike Niemeier ◽  
Daniele Visioni ◽  
Simone Tilmes ◽  
Harri Kokkola
Keyword(s):  
Sulfuric Acid ◽  
Solar Radiation ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Local Minimum ◽  
Climate Impacts ◽  
Injection Strategy ◽  
Injection Strategies ◽  
Stratospheric Aerosols ◽  
Injection Rates

Abstract. Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied options for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate for the greenhouse-gas-induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now, it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used – that is, if aerosols are represented by a modal or sectional distribution. Here, we have studied different spatio-temporal injection strategies with different injection magnitudes using the aerosol–climate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA (Sectional Aerosol module for Large Scale Applications) and the modal module M7. We found significant differences in the model responses depending on the aerosol microphysical module used. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced an 88 %–154 % higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 100 Tg (S) yr−1. These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles in the SALSA module, most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation in the M7 module. Thus, the effective radii of stratospheric aerosols were 10 %–52 % larger in M7 than in SALSA, depending on the injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in the aerosol number size distribution between the accumulation and coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rates using SALSA, the most efficient studied injection strategy produced a 33 %–42 % radiative forcing compared with the least efficient strategy, whereas simulations with M7 showed an even larger difference of 48 %–116 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depend on both the injection strategy and the aerosol microphysical model. Overall, these results highlight the crucial impact of aerosol microphysics on the physical properties of stratospheric aerosol which, in turn, causes significant uncertainties in estimating the climate impacts of stratospheric sulfur injections.

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 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 Nonlinear Effects of Coexisting Surface and Atmospheric Forcing of Anthropogenic Absorbing Aerosols: Impact on the South Asian Monsoon Onset

2013 ◽  
Vol 26 (15) ◽  
pp. 5594-5607 ◽  
Author(s):  
Shao-Yi Lee ◽  
Ho-Jeong Shin ◽  
Chien Wang
Keyword(s):  
Indian Subcontinent ◽  
Critical Factor ◽  
Nonlinear Effects ◽  
Monsoon Onset ◽  
Climate Impacts ◽  
Monsoon Circulation ◽  
The South ◽  
Surface Cooling ◽  
Atmospheric Heating ◽  
Absorbing Aerosols

Abstract The direct radiative effect of absorbing aerosols consists of absorption-induced atmospheric heating together with scattering- and absorption-induced surface cooling. It is thus important to understand whether some of the reported climate impacts of anthropogenic absorbing aerosols are mainly due to the coexistence of these two opposite effects and to what extent the nonlinearity raised from such coexistence would become a critical factor. To answer these questions specifically regarding the South Asia summer monsoon with focus on aerosol-induced changes in monsoon onset, a set of century-long simulations using the Community Earth System Model, version 1.0.3 (CESM 1.0.3), of NCAR with fully coupled atmosphere and ocean components was conducted. Prescribed direct heating to the atmosphere and cooling to the surface were applied in the simulations over the Indian subcontinent, either alone or combined, during the aerosol-laden months of May and June. Over many places in the Indian subcontinent, the nonlinear effect dominates in the changes of subcloud layer moist static energy, precipitation, and monsoon onset. The surface cooling effect of aerosols appears to shift anomalous precipitative cooling away from the aerosol-forcing region and hence turn the negative feedback to aerosol-induced atmospheric heating into a positive feedback on the monsoon circulation through latent heat release over the Himalayan foothills. Moisture processes form the critical chain mediating local aerosol direct effects and onset changes in the monsoon system.

scholarly journals Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy part 1: Intercomparison of modal and sectional aerosol module

2021 ◽  
Author(s):  
Anton Laakso ◽  
Ulrike Niemeier ◽  
Daniele Visioni ◽  
Simone Tilmes ◽  
Harri Kokkola
Keyword(s):  
Sulfuric Acid ◽  
Solar Radiation ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Local Minimum ◽  
Injection Rate ◽  
Climate Impacts ◽  
Solar Radiation Management ◽  
Injection Strategy ◽  
Stratospheric Aerosols

Abstract. Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied option for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate the greenhouse gas induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used, that is, if aerosols are represented by modal or sectional distribution. Here, we have studied different spatio-temporal injections strategies with different injection magnitudes by using the aerosol-climate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA and the modal module M7. We found significant differences in model responses depending on the used aerosol microphysical module. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced 88 %–154 % higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 1 to 100 Tg(S) yr−1. These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while in SALSA injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles, in M7 most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation. Thus, the effective radii of stratospheric aerosols were 10–52% larger in M7 than in SALSA, depending on injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in aerosol number size distribution between the accumulation and the coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rate using SALSA, the most efficient studied injection strategy produced 33–42 % radiative forcing compared to the least efficient strategy while simulations with M7 showed even larger difference of 48–76 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depends both on the injection strategy and the aerosol microphysical model. Overall, these results highlight a crucial role of aerosol microphysics on the physical properties of stratospheric aerosol which in turn causes significant uncertainties in estimating climate impacts of stratospheric sulfur injections.

scholarly journals The sensitivity of tropical convective precipitation to the direct radiative forcings of black carbon aerosols emitted from major regions

2009 ◽  
Vol 27 (10) ◽  
pp. 3705-3711 ◽  
Author(s):  
C. Wang
Keyword(s):  
Atlantic Ocean ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Convective Precipitation ◽  
Anthropogenic Aerosols ◽  
Solar Absorption ◽  
Radiative Forcings ◽  
Aerosol Forcing ◽  
Depth Analysis ◽  
Bc Aerosols

Abstract. Previous works have suggested that the direct radiative forcing (DRF) of black carbon (BC) aerosols are able to force a significant change in tropical convective precipitation ranging from the Pacific and Indian Ocean to the Atlantic Ocean. In this in-depth analysis, the sensitivity of this modeled effect of BC on tropical convective precipitation to the emissions of BC from 5 major regions of the world has been examined. In a zonal mean base, the effect of BC on tropical convective precipitation is a result of a displacement of ITCZ toward the forcing (warming) hemisphere. However, a substantial difference exists in this effect associated with BC over different continents. The BC effect on convective precipitation over the tropical Pacific Ocean is found to be most sensitive to the emissions from Central and North America due to a persistent presence of BC aerosols from these two regions in the lowermost troposphere over the Eastern Pacific. The BC effect over the tropical Indian and Atlantic Ocean is most sensitive to the emissions from South as well as East Asia and Africa, respectively. Interestingly, the summation of these individual effects associated with emissions from various regions mostly exceeds their actual combined effect as shown in the model run driven by the global BC emissions, so that they must offset each other in certain locations and a nonlinearity of this type of effect is thus defined. It is known that anthropogenic aerosols contain many scattering-dominant constituents that might exert an effect opposite to that of absorbing BC. The combined aerosol forcing is thus likely differing from the BC-only one. Nevertheless, this study along with others of its kind that isolates the DRF of BC from other forcings provides an insight of the potentially important climate response to anthropogenic forcings particularly related to the unique particulate solar absorption.

scholarly journals Significant climate impacts of aerosol changes driven by growth in energy use and advances in emission control technology

2019 ◽  
Vol 19 (23) ◽  
pp. 14517-14533 ◽  
Author(s):  
Alcide Zhao ◽  
Massimo A. Bollasina ◽  
Monica Crippa ◽  
David S. Stevenson
Keyword(s):  
Radiative Forcing ◽  
Energy Use ◽  
Emission Control ◽  
Climate Impacts ◽  
Future Climate Change ◽  
Control Technology ◽  
Anthropogenic Aerosols ◽  
Linear Processes ◽  
Impact Reduction ◽  
Global Mean

Abstract. Anthropogenic aerosols have increased significantly since the industrial revolution, driven largely by growth in emissions from energy use in sectors including power generation, industry, and transport. Advances in emission control technologies since around 1970, however, have partially counteracted emissions increases from the above sectors. Using the fully coupled Community Earth System Model, we quantify the effective radiative forcing (ERF) and climate response to 1970–2010 aerosol changes associated with the above two policy-relevant emission drivers. Emissions from energy-use growth generate a global mean aerosol ERF (mean ± 1 standard deviation) of -0.31±0.22 W m−2 and result in a global mean cooling (-0.35±0.17 K) and a precipitation reduction (-0.03±0.02 mm d−1). By contrast, the avoided emissions from advances in emission control technology, which benefit air quality, generate a global mean ERF of +0.21±0.23 W m−2, a global warming of +0.10±0.13 K, and global mean precipitation increase of +0.01±0.02 mm d−1. Despite the relatively small changes in global mean precipitation, these two emission drivers have profound impacts at regional scales, in particular over Asia and Europe. The total net aerosol impacts on climate are dominated by energy-use growth, from Asia in particular. However, technology advances outweigh energy-use growth over Europe and North America. Various non-linear processes are involved along the pathway from aerosol and their precursor emissions to radiative forcing and ultimately to climate responses, suggesting that the diagnosed aerosol forcing and effects must be interpreted in the context of experiment designs. Further, the temperature response per unit aerosol ERF varies significantly across many factors, including location and magnitude of emission changes, implying that ERF, and the related metrics, needs to be used very carefully for aerosols. Future aerosol-related emission pathways have large temporal and spatial uncertainties; our findings provide useful information for both assessing and interpreting such uncertainties, and they may help inform future climate change impact reduction strategies.

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