Biomass smoke from southern Africa can significantly enhance the brightness of stratocumulus over the southeastern Atlantic Ocean

Lu, Zheng; Liu, Xiaohong; Zhang, Zhibo; Zhao, Chun; Meyer, Kerry; Rajapakshe, Chamara; Wu, Chenglai; Yang, Zhifeng; Penner, Joyce E.

doi:10.1073/pnas.1713703115

Cited by 114 publications

(112 citation statements)

References 39 publications

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“…This is confirmed by the increase in cloud top height and cloud top entrainment found by Lu et al (2018) in the presence of biomass burning, opposite to our result. They also average over pristine periods without much smoke aerosol, while we quote results only in a very polluted period.…”

Section: Comparison With Other Studiescontrasting

confidence: 65%

“…Comparing to another regional modelling study, we simulate similar precipitation rates to Lu et al (2018) are not the same so this good agreement could be coincidental: we expect that in our spatial domain Lu et al (2018) would predict a higher rain rate than their domain average, because their domain includes much more of the mainly non-precipitating stratocumulus deck than ours.…”

supporting

confidence: 66%

“…While Lu et al (2018) do not separate direct and semi-direct radiative effects in their regional WRF simulations, and the effects have opposite signs so are not constrained to be small, we can speculate, based on the very small changes in LWP between their 'M' and 'P' (default) simulations, that their time-averaged semi-direct effect must be substantially smaller than 15 that in our regional model for the last five days of August 2016. This is confirmed by the increase in cloud top height and cloud top entrainment found by Lu et al (2018) in the presence of biomass burning, opposite to our result.…”

Section: Comparison With Other Studiesmentioning

confidence: 57%

“…Our indirect radiative effects can also be compared to the 'remote' results in the WRF regional modelling study of Lu et al (2018). When averaging over a two-month period, the authors find a time-averaged indirect effect of −6.12 W m ), while we simulate an increase of a factor 3.…”

Section: Comparison With Other Studiesmentioning

confidence: 74%

“…A noteworthy regional modelling study of the south-east Atlantic by Lu et al (2018) using the WRF model was published as this manuscript was being prepared for submission. The authors studied a 16 × 20…”

Section: Introductionmentioning

confidence: 99%

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Large simulated radiative effects of smoke in the south-east Atlantic

Gordon¹,

Field²,

Abel³

et al. 2018

Preprint

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Abstract. A 1200 km-square area of the tropical south Atlantic Ocean near Ascension Island is studied with the HadGEM climate model at convection-permitting and global resolutions for a ten-day case study period in August 2016. During the simulation period, a plume of biomass burning smoke from Africa moves into the area and mixes into the clouds. We examine the interaction of the smoke with clouds and find it has substantial instantaneous direct, indirect and semi-direct radiative effects, which vary in magnitude between model configurations. The smoke aerosol is simulated realistically, and is found to affect dynamical, microphysical and radiative properties of the 10 atmosphere across the region. The model captures the large-scale horizontal transport of the aerosol adequately, approximately reproducing a transition from pristine to polluted conditions. However, for some of the simulation, the smoke is around 1km too low in altitude and therefore mixes into the clouds earlier than observed. Fire emissions increase the total aerosol burden by a factor 3.7 and cloud droplet number concentrations by a factor of 3, which is consistent with MODIS observations. Strong localised perturbations to heating and cooling rates due to the smoke affect the dynamics: in the regional model, the inversion relative to a simulation without smoke aerosol, when averaged over the polluted period. This increase is uncertain, and smaller in the global model. It is mostly due to radiatively driven dynamical changes: the reduced entrainment of dry air from above the cloud layer, rather than precipitation suppression by aerosol. 20The smoke has substantial direct radiative effects of +11.4 W m . However, the radiative effects are sensitive to the model set-up: the semi-direct effect is smaller in the global model, and also in a simulation with the Kogan (2013) parameterisation of autoconversion and accretion instead of the default, from Khairoutdinov & Kogan (2002). Furthermore, we simulate a liquid water path that is biased high compared to 25 satellite observations by 22% on average, and this leads to high estimates of the domain-averaged aerosol direct effect and the effect of the aerosol on cloud albedo. With these caveats, we simulate a large net cooling across the region, of −27.6 W m

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Section: Comparison With Other Studiescontrasting

confidence: 65%

supporting

confidence: 66%

Section: Comparison With Other Studiesmentioning

confidence: 57%

Section: Comparison With Other Studiesmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

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Large simulated radiative effects of smoke in the south-east Atlantic

Gordon¹,

Field²,

Abel³

et al. 2018

Preprint

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The Ascension Island Boundary Layer in the Remote Southeast Atlantic is Often Smoky

Zuidema

Sedlacek

Flynn

et al. 2018

Geophysical Research Letters

118

166

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Observations from June to October 2016, from a surface‐based ARM Mobile Facility deployment on Ascension Island (8°S, 14.5°W) indicate that refractory black carbon (rBC) is almost always present within the boundary layer. The rBC mass concentrations, light absorption coefficients, and cloud condensation nuclei concentrations vary in concert and synoptically, peaking in August. Light absorption coefficients at three visible wavelengths as a function of rBC mass are approximately double that calculated from black carbon in lab studies. A spectrally‐flat absorption angstrom exponent suggests most of the light absorption is from lens‐coated black carbon. The single‐scattering‐albedo increases systematically from August to October in both 2016 and 2017, with monthly means of 0.78 ± 0.02 (August), 0.81 ± 0.03 (September), and 0.83 ± 0.03 (October) at the green wavelength. Boundary layer aerosol loadings are only loosely correlated with total aerosol optical depth, with smoke more likely to be present in the boundary layer earlier in the biomass burning season, evolving to smoke predominantly present above the cloud layers in September–October, typically resting upon the cloud top inversion. The time period with the campaign‐maximum near‐surface light absorption and column aerosol optical depth, on 13–16 August 2016, is investigated further. Backtrajectories that indicate more direct boundary layer transport westward from the African continent is central to explaining the elevated surface aerosol loadings.

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Water Vapor and Pollutants, Aerosol–Cloud Interactions

Prabha

Хаин

2019

Encyclopedia of Water

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Clouds, to a great extent, govern the radiation balance and energy fluxes reaching Earth and have a strong impact on the hydrological cycle and freshwater distribution over the globe. Latent heat release in clouds is the energy source for atmospheric phenomena from cloud scale to global circulation. Changes in cloud microphysical and radiative properties impact weather and climate and contribute in changing climate. All of these determine the vital impact that clouds exert on all forms of life on the planet, human life included. Studies of clouds and cloud‐related phenomena are an integral part of modern meteorology, providing data with direct application in weather forecasting, agriculture, environment control, air traffic control, and many other spheres of human activity. Natural and anthropogenic aerosol particles affect cloud properties and precipitation regimes and continue to be a growing field of research. A significant progress has been achieved in understanding cloud processes and aerosol–cloud interaction during last decade. At the same time some processes, especially those related to ice phase remain uncertain and require further investigation. A review of major processes related to aerosol effects and specially to aerosol–cloud interaction is presented.

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Biomass smoke from southern Africa can significantly enhance the brightness of stratocumulus over the southeastern Atlantic Ocean

Cited by 114 publications

References 39 publications

Large simulated radiative effects of smoke in the south-east Atlantic

Large simulated radiative effects of smoke in the south-east Atlantic

The Ascension Island Boundary Layer in the Remote Southeast Atlantic is Often Smoky

Water Vapor and Pollutants, Aerosol–Cloud Interactions

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