Global evidence of aerosol-induced invigoration in marine cumulus clouds

Douglas, Alyson; L’Ecuyer, Tristan

doi:10.5194/acp-21-15103-2021

Cited by 10 publications

(7 citation statements)

References 58 publications

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“…However, cloud thinning by entrainment can be compensated by other processes, potentially causing a net deepening effect. This invites us to think of new mechanisms to explain cloud deepening: warm cloud invigoration (Douglas and L'Ecuyer, 2021) or aerosol-induced rain delays and subsequent cloud layer growth (Seifert et al, 2015;Vogel et al, 2016).…”

Section: Cloud Deepeningmentioning

confidence: 99%

“…Cloud deepening could be driven by large-scale meteorological changes, or it could be locally driven by entrainment under a weak inversion. Because the clouds have cumuliform features in ICON, it is also possible that other processes, such as cloud deepening from delayed precipitation (Seifert et al, 2015), or aerosol-induced warm cloud invigoration (Douglas and L'Ecuyer, 2021), are driving cloud deepening and LWP increases on top of the precipitation response.…”

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confidence: 99%

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Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Fons,

Naumann,

Neubauer

et al. 2024

Preprint

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Abstract. Since pre-industrial times, aerosol emissions have caused brightening of stratocumulus clouds, thereby cooling the climate. However, observational studies and climate models disagree on the magnitude of this cooling, in particular because of the liquid water path (LWP) response of stratocumulus clouds to increasing aerosols, with climate models predicting an increase in LWP, and satellites observing a weak decrease. With higher-resolution global climate models, there is hope to bridge this gap. In this study, we present simulations conducted with the ICOsahedral Non-hydrostatic climate model (ICON) used as a global storm-resolving model (GSRM) with 5 km horizontal resolution. We compare the model outputs with geostationary satellite data, and we observe that, while ICON produces realistic low-cloud cover in the stratocumulus regions, these clouds look cumuliform and the sign of LWP adjustments to aerosols disagrees with satellite data. We evaluate this disagreement with a causal approach, which combines time series with knowledge of cloud processes in the form of a causal graph, allowing us to diagnose the sources of discrepancies between satellite and model studies. We find that the positive LWP adjustment to increasing aerosols in ICON results from a superposition of processes, with an overestimated positive response due to precipitation suppression and cloud deepening under a weak inversion, despite small negative influences from cloud-top entrainment enhancement. Such analyses constitute a methodology that can guide modelers on how to modify model parameterizations and set-ups to reconcile conflicting studies concerning the sign and magnitude of LWP adjustments across different data sources.

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Section: Cloud Deepeningmentioning

confidence: 99%

mentioning

confidence: 99%

Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Fons,

Naumann,

Neubauer

et al. 2024

Preprint

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“…Among the many properties that affect cloud formation and evolution, aerosols play an important role. In presence of a high concentration of water‐friendly particles acting as cloud condensation nuclei (CCN), a large number of small droplets are activated, leading to low auto conversion and collision rates, prolonging cloud lifetime (Albrecht, 1989), favoring evaporation when dry air is entrained in the cloud (Ackerman et al, 2004; Jiang et al, 2006), and modifying the release of latent heat, which drives the air buoyancy (Douglas & L'Ecuyer, 2021). While aerosols can also delay the onset precipitation (Lonitz et al, 2015; Spill et al, 2019), the change in rain mass with aerosol depends on environmental conditions, which affect droplet growth rate by collision and the evaporation rate (Douglas & L'Ecuyer, 2021; Khain et al, 2008; Lonitz et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Low cloud response to aerosol‐radiation‐cloud interactions: Idealized WRF numerical experiments for EUREC⁴A project

Tartaglione,

Desbiolles,

del Moral‐Méndez

et al. 2024

Atmospheric Science Letters

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Aerosols significantly affect cloud microphysics and energy budget in different ways. The contribution of the direct, semi‐direct, and indirect effects of aerosols on radiation are here investigated over the North Atlantic tropical ocean under different aerosol loadings. The Weather Research and Forecasting Model is used to perform a set of numerical idealized experiments, which are forced with prescribed aerosol profiles. We evaluate the effects of aerosols on modeled shallow clouds and surface radiative budget. The results indicate that large aerosol loadings are associated with enhanced cloudiness and reduced precipitation. While the change in rainfall is mainly due to the larger number of smaller droplets, the change in cloudiness is attributed to the effects of absorbing aerosols, mainly dust particles, which are responsible for a rise of temperature that feeds back onto specific humidity. As in the boundary layer the increase of moisture dominates, the net effect is a higher relative humidity, which favors the formation of thin low non‐precipitating clouds. The feedback accounts for a dynamical change in the lower troposphere: shortwave radiation absorption increases temperature at the top of the marine atmospheric boundary‐layer and reduces entrainment of warm and dry air, increasing low level moisture content. Despite the overall increase in cloudiness, daytime cloud cover is reduced. The semi‐direct effect of aerosols on clouds results in a warming of the surface, opposite to the indirect effect.

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“…Depending on the types of aerosols and clouds, their interaction might either decrease or increase the susceptibility of clouds to form rain (Rosenfeld et al, 2008). While observational evidence of the invigoration effect is still ambiguous (Fan et al, 2018;Douglas and L'Ecuyer, 2021;Igel and van den Heever, 2021;Romps et al, 2023), effects of aerosols on cloud glaciation have barely been studied on a global scale due to a lack of both suitable INP proxies (Villanueva et al, 2020) and reliable longterm observations of ice-containing clouds (Villanueva et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

A cloud-by-cloud approach for studying aerosol–cloud interaction in satellite observations

Alexandri,

Müller,

Choudhury

et al. 2024

Atmos. Meas. Tech.

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Abstract. The effective radiative forcing (ERF) due to aerosol–cloud interactions (ACIs) and rapid adjustments (ERFaci) still causes the largest uncertainty in the assessment of climate change. It is understood only with medium confidence and is studied primarily for warm clouds. Here, we present a novel cloud-by-cloud (C×C) approach for studying ACI in satellite observations that combines the concentration of cloud condensation nuclei (nCCN) and ice nucleating particles (nINP) from polar-orbiting lidar measurements with the development of the properties of individual clouds by tracking them in geostationary observations. We present a step-by-step description for obtaining matched aerosol–cloud cases. The application to satellite observations over central Europe and northern Africa during 2014, together with rigorous quality assurance, leads to 399 liquid-only clouds and 95 ice-containing clouds that can be matched to surrounding nCCN and nINP respectively at cloud level. We use this initial data set for assessing the impact of changes in cloud-relevant aerosol concentrations on the cloud droplet number concentration (Nd) and effective radius (reff) of liquid clouds and the phase of clouds in the regime of heterogeneous ice formation. We find a Δln⁡Nd/Δln⁡nCCN of 0.13 to 0.30, which is at the lower end of commonly inferred values of 0.3 to 0.8. The Δln⁡reff/Δln⁡nCCN between −0.09 and −0.21 suggests that reff decreases by −0.81 to −3.78 nm per increase in nCCN of 1 cm−3. We also find a tendency towards more cloud ice and more fully glaciated clouds with increasing nINP that cannot be explained by the increasingly lower cloud top temperature of supercooled-liquid, mixed-phase, and fully glaciated clouds alone. Applied to a larger number of observations, the C×C approach has the potential to enable the systematic investigation of warm and cold clouds. This marks a step change in the quantification of ERFaci from space.

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Global evidence of aerosol-induced invigoration in marine cumulus clouds

Cited by 10 publications

References 58 publications

Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Low cloud response to aerosol‐radiation‐cloud interactions: Idealized WRF numerical experiments for EUREC⁴A project

A cloud-by-cloud approach for studying aerosol–cloud interaction in satellite observations

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Global evidence of aerosol-induced invigoration in marine cumulus clouds

Cited by 10 publications

References 58 publications

Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON

Low cloud response to aerosol‐radiation‐cloud interactions: Idealized WRF numerical experiments for EUREC4A project

A cloud-by-cloud approach for studying aerosol–cloud interaction in satellite observations

Contact Info

Product

Resources

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Low cloud response to aerosol‐radiation‐cloud interactions: Idealized WRF numerical experiments for EUREC⁴A project