scholarly journals The Impact of Process‐Based Warm Rain Constraints on the Aerosol Indirect Effect

2018 ◽  
Vol 45 (19) ◽  
pp. 10,729-10,737 ◽  
Author(s):  
Xianwen Jing ◽  
Kentaroh Suzuki
Keyword(s):  
Indirect Effect ◽  
Aerosol Indirect Effect ◽  
Warm Rain ◽  
The Impact

scholarly journals Effects of near-source coagulation of biomass burning aerosols on global predictions of aerosol size distributions and implications for aerosol radiative effects

2019 ◽  
Vol 19 (9) ◽  
pp. 6561-6577 ◽  
Author(s):  
Emily Ramnarine ◽  
John K. Kodros ◽  
Anna L. Hodshire ◽  
Chantelle R. Lonsdale ◽  
Matthew J. Alvarado ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Indirect Effect ◽  
Size Distributions ◽  
Aerosol Indirect Effect ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models have ignored sub-grid coagulation and instantly mixed fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this paper, we use this parameterization of sub-grid coagulation in the GEOS-Chem–TOMAS (TwO-Moment Aerosol Sectional) global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect. We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80 nm (a proxy for CCN-sized particles) by 37 % globally. This cloud condensation nuclei (CCN) reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from −76 to −43 mW m−2. Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from −224 to −231 mW m−2, with assumed external mixing of black carbon and from −188 to −197 mW m−2 and with assumed internal mixing of black carbon with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagulation to two different biomass burning emission inventories to various assumptions about the fresh biomass burning aerosol size distribution and to two different timescales of sub-grid coagulation. The impacts of sub-grid coagulation are qualitatively the same regardless of these assumptions.

scholarly journals Effects of Near-Source Coagulation of Biomass Burning Aerosols on Global Predictions of Aerosol Size Distributions and Implications for Aerosol Radiative Effects

2018 ◽  
Author(s):  
Emily Ramnarine ◽  
John K. Kodros ◽  
Anna L. Hodshire ◽  
Chantelle R. Lonsdale ◽  
Matthew J. Alvarado ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Indirect Effect ◽  
Size Distributions ◽  
Aerosol Indirect Effect ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models ignore sub-grid coagulation and instantly mix fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this paper, we use this parameterization of sub-grid coagulation in the GEOS-Chem-TOMAS global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect. We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80 nm (a proxy for CCN-sized particles) by 37 % globally. This CCN reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from −76 to −43 mW m−2. Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from −224 to −231 mW m−2 with assumed external mixing and from −188 to −197 mW m−2 with assumed internal mixing with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagulation to two different biomass burning emission inventories, to various assumptions about the fresh biomass burning aerosol size distribution, and to two different timescales of sub-grid coagulation. The impacts of sub-grid coagulation are qualitatively the same regardless of these assumptions.

scholarly journals The Key Role of Warm Rain Parameterization in Determining the Aerosol Indirect Effect in a Global Climate Model

2019 ◽  
Vol 32 (14) ◽  
pp. 4409-4430 ◽  
Author(s):  
Xianwen Jing ◽  
Kentaroh Suzuki ◽  
Takuro Michibata
Keyword(s):  
Indirect Effect ◽  
Formation Process ◽  
Global Climate ◽  
Satellite Observations ◽  
Past Century ◽  
Formation Processes ◽  
Aerosol Indirect Effect ◽  
Warm Rain ◽  
Rain Formation

AbstractGlobal climate models (GCMs) have been found to share the common too-frequent bias in the warm rain formation process. In this study, five different autoconversion schemes are incorporated into a single GCM, to systematically evaluate the warm rain formation processes in comparison with satellite observations and investigate their effects on the aerosol indirect effect (AIE). It is found that some schemes generate warm rain less efficiently under polluted conditions in the manner closer to satellite observations, while the others generate warm rain too frequently. Large differences in AIE are found among these schemes. It is remarkable that the schemes with more observation-like warm rain formation processes exhibit larger AIEs that far exceed the uncertainty range reported in IPCC AR5, to an extent that can cancel much of the warming trend in the past century, whereas schemes with too-frequent rain formations yield AIEs that are well bounded by the reported range. The power-law dependence of the autoconversion rate on the cloud droplet number concentration β is found to affect substantially the susceptibility of rain formation to aerosols: the more negative β is, the more difficult it is for rain to be triggered in polluted clouds, leading to larger AIE through substantial contributions from the wet scavenging feedback. The appropriate use of a droplet size threshold can mitigate the effect of a less negative β. The role of the warm rain formation process on AIE in this particular model has broad implications for others that share the too-frequent rain-formation bias.

scholarly journals Weak global sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO<sub>2</sub> chemistry

2013 ◽  
Vol 13 (6) ◽  
pp. 3163-3176 ◽  
Author(s):  
J. R. Pierce ◽  
M. J. Evans ◽  
C. E. Scott ◽  
S. D. D'Andrea ◽  
D. K. Farmer ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Indirect Effect ◽  
Cloud Condensation Nuclei ◽  
Chemical Mechanism ◽  
Model Parameters ◽  
Condensation Nuclei ◽  
Aerosol Indirect Effect ◽  
Global Sensitivity ◽  
Cloud Albedo ◽  
The Impact

Abstract. H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes with important roles in the global aerosol budget and hence planetary radiative forcing. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. For the first time in a global model, we investigate the impact of this new source of H2SO4 in the atmosphere. We use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H2SO4 by 4%. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10–25% in forested NH boundary layers (up to 100% in July) due to CI+SO2 chemistry, but the change is generally negligible elsewhere. The predicted changes in CCN were strongly dampened to the CI+SO2 changes in H2SO4 in some regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03 W m−2. The model global sensitivity of CCN and the AIE to CI+SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA (secondary organic aerosol) and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model-predicted size distributions. We conclude that improvement in the modeled CI+SO2 chemistry would not likely lead to significant improvements in present-day CCN and AIE predictions.

scholarly journals Study of the Aerosol Indirect Effect by Large-Eddy Simulation of Marine Stratocumulus

2005 ◽  
Vol 62 (11) ◽  
pp. 3909-3932 ◽  
Author(s):  
Miao-Ling Lu ◽  
John H. Seinfeld
Keyword(s):  
Indirect Effect ◽  
Large Scale ◽  
Sea Salt ◽  
Relative Reduction ◽  
Cloud Droplets ◽  
Marine Stratocumulus ◽  
Aerosol Indirect Effect ◽  
Sea Salt Aerosol ◽  
Large Eddy ◽  
The Impact

Abstract A total of 98 three-dimensional large-eddy simulations (LESs) of marine stratocumulus clouds covering both nighttime and daytime conditions were performed to explore the response of cloud optical depth (τ) to various aerosol number concentrations (Na = 50–2500 cm−3) and the covarying meteorological conditions (large-scale divergence rate and SST). The idealized First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) and the Atlantic Stratocumulus Transition Experiment (ASTEX) Lagrangian 1 sounding profiles were used to represent the lightly and heavily drizzling cases, respectively. The first and second aerosol indirect effects are identified. Through statistical analysis, τ is found be to both positively correlated with Na and cloud liquid water path (LWP) with a higher correlation associated with LWP, which is predominantly regulated by large-scale subsidence and SST. Clouds with high LWP occur under low SST or weak large-scale subsidence. Introduction of a small amount of giant sea salt aerosol into the simulation lowers the number of cloud droplets activated, results in larger cloud droplets, and initiates precipitation for nondrizzling polluted clouds or precedes the precipitation process for drizzling clouds. However, giant sea salt aerosol is found to have a negligible effect on τ for lightly precipitating cases, while resulting in a relative reduction of τ of 3%–77% (increasing with Na, for Na = 1000–2500 cm−3) for heavily precipitating cases, suggesting that the impact of giant sea salt is only important for moist and potentially convective clouds. Finally, a regression analysis of the simulations shows that the second indirect effect is more evident in clear than polluted cases. The second indirect effect is found to enhance (reduce) the overall aerosol indirect effect for heavily (lightly) drizzling clouds; that is, τ is larger (smaller) for the same relative change in Na than considering the Twomey (first indirect) effect alone. The aerosol indirect effect (on τ) is lessened in the daytime afternoon conditions and is dominated by the Twomey effect; however, the effect in the early morning is close but slightly smaller than that in the nocturnal run. Diurnal variations of the aerosol indirect effect should be considered to accurately assess its magnitude.

scholarly journals Impacts of aerosol indirect effect on past and future changes in tropospheric composition

2009 ◽  
Vol 9 (1) ◽  
pp. 4691-4725 ◽  
Author(s):  
N. Unger ◽  
S. Menon ◽  
D. T. Shindell ◽  
D. M. Koch
Keyword(s):  
Air Quality ◽  
Indirect Effect ◽  
Wet Deposition ◽  
Tropospheric Chemistry ◽  
Atmospheric Composition ◽  
Aerosol Indirect Effect ◽  
Sulfate Production ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions ◽  
The Impact

Abstract. The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, the aerosol indirect effect (AIE). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embrace a wide spectrum of precursor emission changes and consequential aerosol-cloud interactions. The AIE is estimated to be −2.0 W m−2 for PD–PI and −0.6 W m−2 for 2050–PD, at the high end of current estimates. Inclusion of aerosol-cloud interactions substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of aerosol-cloud effects leads to 20% enhancements in in-cloud sulfate production and ~10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions (~10–30%). Nitric acid wet deposition is dampened by 15–20% across the industrialized regions due to AIE allowing additional re-release of reactive nitrogen that contributes to 1–2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that aerosol-cloud interactions must be considered in studies of methane trends and projections of future changes to particulate matter air quality.

scholarly journals Explicit representation of subgrid variability in cloud microphysics yields weaker aerosol indirect effect in the ECHAM5-HAM2 climate model

2015 ◽  
Vol 15 (2) ◽  
pp. 703-714 ◽  
Author(s):  
J. Tonttila ◽  
H. Järvinen ◽  
P. Räisänen
Keyword(s):  
Indirect Effect ◽  
Radiative Forcing ◽  
Climate Model ◽  
Cloud Microphysics ◽  
Radiation Balance ◽  
Anthropogenic Aerosols ◽  
Aerosol Indirect Effect ◽  
Cloud Activation ◽  
The Impact ◽  
Global Mean

Abstract. The impacts of representing cloud microphysical processes in a stochastic subcolumn framework are investigated, with emphasis on estimating the aerosol indirect effect. It is shown that subgrid treatment of cloud activation and autoconversion of cloud water to rain reduce the impact of anthropogenic aerosols on cloud properties and thus reduce the global mean aerosol indirect effect by 19%, from −1.59 to −1.28 W m−2. This difference is partly related to differences in the model basic state; in particular, the liquid water path (LWP) is smaller and the shortwave cloud radiative forcing weaker when autoconversion is computed separately for each subcolumn. However, when the model is retuned so that the differences in the basic state LWP and radiation balance are largely eliminated, the global-mean aerosol indirect effect is still 14% smaller (i.e. −1.37 W m−2) than for the model version without subgrid treatment of cloud activation and autoconversion. The results show the importance of considering subgrid variability in the treatment of autoconversion. Representation of several processes in a self-consistent subgrid framework is emphasized. This paper provides evidence that omitting subgrid variability in cloud microphysics contributes to the apparently chronic overestimation of the aerosol indirect effect by climate models, as compared to satellite-based estimates.

scholarly journals Explicit representation of subgrid variability in cloud microphysics yields weaker aerosol indirect effect in the ECHAM5-HAM2 climate model

2014 ◽  
Vol 14 (10) ◽  
pp. 15523-15543
Author(s):  
J. Tonttila ◽  
H. Järvinen ◽  
P. Räisänen
Keyword(s):  
Indirect Effect ◽  
Climate Models ◽  
Climate Model ◽  
Cloud Microphysics ◽  
Anthropogenic Aerosols ◽  
Aerosol Indirect Effect ◽  
Cloud Properties ◽  
Microphysical Processes ◽  
Cloud Activation ◽  
The Impact

Abstract. Impacts of representing cloud microphysical processes in a stochastic subcolumn framework are investigated, with emphasis on estimating the aerosol indirect effect. It is shown that subgrid treatment of cloud activation and autoconversion of cloud water to rain reduce the impact of anthropogenic aerosols on cloud properties and thus reduce the global mean aerosol indirect effect by 18%, from 1.59 to 1.30 W m−2. Although the results show the importance of considering subgrid variability in the treatment of autoconversion, representing several processes in a self-consistent subgrid framework is emphasized. This paper provides direct evidence that omitting subgrid variability in cloud microphysics significantly contributes to the apparently chronic overestimation of the aerosol indirect effect by climate models, as compared to satellite-based estimates.

scholarly journals The Impact of Managers and Network Interactions on the Integration of Circularity in Business Strategy

2021 ◽  
pp. 108602662199463
Author(s):  
Manon Eikelenboom ◽  
Gjalt de Jong
Keyword(s):  
The Netherlands ◽  
Survey Data ◽  
Empirical Research ◽  
Indirect Effect ◽  
Business Strategy ◽  
Business Processes ◽  
Core Business ◽  
Organizational Attributes ◽  
Positive Direct ◽  
The Impact

Integrating circularity in business strategy is difficult to achieve for companies as it requires impactful changes in core business processes. While research has focused on identifying key barriers, little is known about the organizational attributes that can assist businesses in integrating circularity in their strategies. The purpose of this study is to investigate the implications of organizational managers and network interactions for the integration of circularity in business strategy. Through using survey data from 627 SMEs (small- and medium-sized enterprises) in the Netherlands, this study shows that managers who interpret circularity as an opportunity can have a positive direct and indirect effect on the integration of circularity in a company’s strategy. The results furthermore highlight the importance of circular network interactions for the integration of circularity in business strategy. This article contributes to recent calls for more empirical research into the integration of circularity and offers relevant insights for companies aiming to integrate circularity.

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