Satellite-based estimate of global aerosol–cloud radiative forcing by marine warm clouds

Chen, Yi-Chun; Christensen, Matthew; Stephens, Graeme L.; Seinfeld, John H.

doi:10.1038/ngeo2214

Cited by 235 publications

(321 citation statements)

References 27 publications

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“…1 but for set 2. snapshots) and 2 transition simulations (low τ a and high τ a ), also at hourly intervals. Such analyses show the relative importance of intrinsic factors (A) or extrinsic factors (f c ) in controlling rCRE (20,22). It is immediately clear that the simulations tend to follow a fairly robust relationship, with rCRE, as expected, increasing progressively with increasing f c and A.…”

Section: Simulation Resultsmentioning

confidence: 86%

“…Current efforts at elucidating this relationship rely on reanalysis (21,22), and although the latter approach is valuable at the regional circulation scale, reanalysis is not reliable enough at the cloud scale. Model−observation comparison at the level of individual microphysical and macrophysical responses to the aerosol (Eq.…”

Section: Discussionmentioning

confidence: 99%

“…3, linearity suggests an independence of A c and f c .) Regardless of the exact form, the (A, f c ) relationship has distinct advantages: It can be addressed with fewer measurements than the Chain Rule expansions, measurement error and uncertainty are more directly linked to CRE, measurements can be made from space and from the ground (19,20), and it captures important underlying physics (21,22). It is currently used as a means of diagnosing AGCM performance (17,18) but, as we will argue below, could be applied to process models as well.…”

Section: Examplesmentioning

confidence: 99%

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New approaches to quantifying aerosol influence on the cloud radiative effect

Feingold

McComiskey

Yamaguchi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphysical entities and, by their very nature, ephemeral and hard to predict. Atmospheric general circulation models represent aerosol−cloud interactions at everincreasing levels of detail, but these models lack the resolution to represent clouds and aerosol−cloud interactions adequately. There is a dearth of observational constraints on aerosol−cloud interactions. We develop a conceptual approach to systematically constrain the aerosol−cloud radiative effect in shallow clouds through a combination of routine process modeling and satellite and surfacebased shortwave radiation measurements. We heed the call to merge Darwinian and Newtonian strategies by balancing microphysical detail with scaling and emergent properties of the aerosol−cloud radiation system.T he climate system, with its couplings between land surface, vegetation, ocean, cryosphere, and atmosphere, is an extraordinarily complex system that is under intensive scrutiny for the purposes of climate analysis and prediction. The atmospheric aerosol and its interaction with clouds is a poorly quantified component of the climate system and is the focus of the current study. The aerosol comprises suspended particles that derive from the oceans, land surface, volcanoes, and anthropogenic activities. The difficulty in quantifying climate forcing by the aerosol emanates partly from the complexity in the aerosol itself, and partly from the fact that its influence on clouds requires detailed understanding of clouds and cloud feedbacks at a range of spatiotemporal scales. Untangling the multiple cloud responses that occur as a result of aerosol perturbations is particularly difficult (1). As one example, consider the influence of the aerosol on clouds and precipitation. Assuming no change in condensed water, the aerosol, by acting as nucleation sites for droplets, might generate smaller droplets, more reflective clouds (2), and reduced precipitation (3). However, through a multitude of complex and contingent pathways, aerosol-perturbed clouds sometimes appear to have similar reflectance because brightening is offset by reductions in cloud water, a fundamental property controlling cloud reflectance. On short timescales (hours), the aerosol tends to reduce precipitation in shallow, liquid-only clouds, but this may be offset over longer periods (multiple days) (4). Deep, mixed-phase convective clouds present even more complex pathways for generation of precipitation, and even more contingencies. The aerosol appears to change the distribution and intensity of surface rain from deep c...

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Section: Simulation Resultsmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Examplesmentioning

confidence: 99%

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New approaches to quantifying aerosol influence on the cloud radiative effect

Feingold

McComiskey

Yamaguchi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Rosenfeld et al, 2014) and the interaction of clouds with the solar and terrestrial radiation (e.g. Boucher and Lohmann, 1995;Ramanathan et al, 2001;Chen et al, 2014). A better understanding is needed with respect to each of these steps in order to improve the performance of the current global climate models (GCMs) and to increase the accuracy of the future climate predictions.…”

Section: Introductionmentioning

confidence: 99%

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

et al. 2015

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Published by Copernicus Publications on behalf of the European Geosciences Union. M. Paramonov et al.: A synthesis of CCNC measurements within the EUCAARI networkAbstract. Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (N CCN ) to the total number concentration of particles (N CN ), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations -exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A 50 and A 100 , respectively) renders a much more stable dependence of A on S; A 50 and A 100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of N CCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of N CCN , total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments.

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“…For example, a reduced stability of the environmental temperature profile can allow for enhanced cloud-droplet growth through increasing convection (Klein and Hartmann, 1993). This would be expected to lead to greater mixing of the aerosols with the cloudy air and greater aerosol impacts on cloud microphysical properties (Chen et al, 2014;Andersen and Cermak, 2015). Also, in the Arctic during the winter, pollution plumes from Asia are often associated with higher values of potential temperature than pollution plumes from Europe (Stohl, 2006).…”

Section: Q Coopman Et Al: Effects Of Pollution On Liquid Clouds In mentioning

confidence: 99%

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

et al. 2016

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Abstract. The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol-cloud interaction (ACI net ) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACI net is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACI net averages 0.12±0.02 for cloud-droplet effective radius and 0.16±0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds.

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Satellite-based estimate of global aerosol–cloud radiative forcing by marine warm clouds

Cited by 235 publications

References 27 publications

New approaches to quantifying aerosol influence on the cloud radiative effect

New approaches to quantifying aerosol influence on the cloud radiative effect

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

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