Quantification of Monthly Mean Regional-Scale Albedo of Marine Stratiform Clouds in Satellite Observations and GCMs

Bender, Frida A.‐M.; Charlson, Robert J.; Ekman, Annica M. L.; Leahy, Louise V.

doi:10.1175/jamc-d-11-049.1

Cited by 45 publications

(76 citation statements)

References 35 publications

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“…Except for the bounding by A s at f c = 0 and by A c at f c = 1, there is no a priori reason why the relationship based on the small spatiotemporal averaging in this work should behave similarly to that from the large spatiotemporal averaging as in ref. 18; differences between the CRM output and the remote sensing data are likely related, among others, to the averaging scale, covariability in meteorology and aerosol, and definition of f c (Fig. S1).…”

Section: Simulation Resultsmentioning

confidence: 99%

“…A c is itself a function of τ, and therefore L and N d . Approximately linear relationships between MODIS (Moderate Resolution Imaging Spectroradiometer)-derived f c and CERES (Clouds and the Earth's Radiant Energy System)-derived A in multiple marine stratocumulus locations have been found when averaging over 2.5°× 2.5°and 1-mo periods (18). (Based on Eq.…”

Section: Examplesmentioning

confidence: 99%

“…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. The (A, f c ) relationship therefore provides a key element of the merged Newtonian−Darwinian approach, i.e., it is an expression of scaling (Harte's "search for patterns and laws").…”

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: 99%

Section: Examplesmentioning

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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“…higher aerosol concentration leading to an increase of the cloud droplet number concentration and a decrease of droplet size at constant liquid water content, with a resulting increase in cloud albedo with increasing amount of aerosol. We use the methods of Bender et al (2011Bender et al ( , 2016 to examine the relation between CDN, LWP, AOD, and cloud albedo in five marine subtropical stratocumulus regions, separating the effects of anthropogenic sulfate and non-sulfate aerosols from the pre-industrial background aerosols.…”

Section: Discussionmentioning

confidence: 99%

“…A method for quantifying cloud albedo on a monthly mean regional scale in climate models and satellite observations was introduced by Bender et al (2011). Hereby, the cloud albedo was determined based on the near-linear relation between cloud fraction and albedo found in five regions of lowaltitude subtropical marine stratocumulus clouds, defined in Klein and Hartmann (1993).…”

Section: Introductionmentioning

confidence: 99%

Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

2017

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Abstract. The effects of different aerosol types on cloud albedo are analysed using the linear relation between total albedo and cloud fraction found on a monthly mean scale in regions of subtropical marine stratocumulus clouds and the influence of simulated aerosol variations on this relation. Model experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to separately study the responses to increases in sulfate, non-sulfate and all anthropogenic aerosols. A cloud brightening on the month-tomonth scale due to variability in the background aerosol is found to dominate even in the cases where anthropogenic aerosols are added. The aerosol composition is of importance for this cloud brightening, that is thereby region dependent. There is indication that absorbing aerosols to some extent counteract the cloud brightening but scene darkening with increasing aerosol burden is generally not supported, even in regions where absorbing aerosols dominate. Month-to-month cloud albedo variability also confirms the importance of liquid water content for cloud albedo. Regional, monthly mean cloud albedo is found to increase with the addition of anthropogenic aerosols and more so with sulfate than non-sulfate. Changes in cloud albedo between experiments are related to changes in cloud water content as well as droplet size distribution changes, so that models with large increases in liquid water path and/or cloud droplet number show large cloud albedo increases with increasing aerosol. However, no clear relation between model sensitivities to aerosol variations on the month-to-month scale and changes in cloud albedo due to changed aerosol burden is found.

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The nonlinear relationship between albedo and cloud fraction on near‐global, monthly mean scale in observations and in the CMIP5 model ensemble

Engström

Bender

Charlson

et al. 2015

Geophysical Research Letters

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We study the relation between monthly mean albedo and cloud fraction over ocean, 60°S–60°N. Satellite observations indicate that these clouds all fall on the same near‐exponential curve, with a monotonic distribution over the ranges of cloud fractions and albedo. Using these observational data as a reference, we examine the degree to which 26 climate models capture this feature of the near‐global marine cloud population. Models show a general increase in albedo with increasing cloud fraction, but none of them display a relation that is as well defined as that characterizing the observations. Models typically display larger albedo variability at a given cloud fraction, larger sensitivity in albedo to changes in cloud fraction, and lower cloud fractions. Several models also show branched distributions, contrasting with the smooth observational relation. In the models the present‐day cloud scenes are more reflective than the preindustrial, demonstrating the simulated impact of anthropogenic aerosols on planetary albedo.

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Quantification of Monthly Mean Regional-Scale Albedo of Marine Stratiform Clouds in Satellite Observations and GCMs

Cited by 45 publications

References 35 publications

New approaches to quantifying aerosol influence on the cloud radiative effect

New approaches to quantifying aerosol influence on the cloud radiative effect

Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

The nonlinear relationship between albedo and cloud fraction on near‐global, monthly mean scale in observations and in the CMIP5 model ensemble

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