A protocol for model intercomparison of impacts of marine cloud brightening climate intervention

Geoscientific model development, Journal Year: 2024, Volume and Issue: 17(21), P. 7963 - 7994

Published: Nov. 8, 2024

Abstract. A modeling protocol (defined by a series of climate model simulations with specified output) is introduced. Studies using these are designed to improve the understanding impacts strategy for intervention (CI) known as marine cloud brightening (MCB) in specific regions; therefore, called MCB-REG (where REG stands region). The not intended assess consequences realistic MCB deployment achieve targets but instead expose responses interventions six regions pervasive systems that often considered candidates such deployment. calibration step involving fixed sea surface temperatures (SSTs) first used identify common forcing, and then coupled forcing individual combinations examine impacts. Synthetic estimates constructed superposing from means approximating produced when introduced multiple regions. few results comparing three modern models (CESM2, E3SMv2, UKESM1) illustrate similarities differences between behavior utility were synthesized summing Cloud aerosol injections differ substantially (CESM2 clouds appear much more susceptible emissions than other models), patterns precipitation temperature similar imposed amplitudes same previously identified La Niña-like response Southeast Pacific evident this study, amplitude was shown markedly across models. Other also found discussed. Forcing Atlantic consistently (across all models) produces weaker global cooling regions, South show strongest cooling. This indicates efficiency given depends on only susceptibility perturbations, strength underlying radiative feedbacks ocean operating within each region. These generally robust models, studies an examination ensembles would be beneficial.

Language: Английский

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Aerosol trends dominate over global warming-induced cloud feedback in driving recent changes in marine low clouds

Research Square (Research Square), Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 13, 2025

Over the past two decades, anthropogenic emission reductions and global warming have impacted marine low clouds through aerosol-cloud interactions (ACI) cloud feedback, yet their quantitative contributions remain unclear. This study employs a deep learning model (CNN_Met−Nd) Community Earth System Model version 2 (CESM2) to disentangle these effects. CNN_Met−Nd reveals that aerosol-driven changes in droplet number concentration dominate near-global shortwave radiative effect (ΔCRE), contributing 0.42 ± 0.08 Wm⁻² per 20 years, compared 0.05 0.37 from feedback. CESM2 effectively reproduces predominant influence of aerosol on ΔCRE by CNN_Met−Nd, lending us confidence for stronger estimate effective forcing due ACI (ERF_aci) -1.29 since preindustrial era. These findings highlight critical role shaping trends its broader climate implications, especially under ongoing reduction efforts.

Language: Английский

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Biological enhancement of cloud droplet concentrations observed off East Antarctica

npj Climate and Atmospheric Science, Journal Year: 2025, Volume and Issue: 8(1)

Published: March 20, 2025

Language: Английский

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Pristine oceans are a significant source of uncertainty in quantifying global cloud condensation nuclei

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(6), P. 3841 - 3856

Published: April 2, 2025

Abstract. Quantifying global cloud condensation nuclei (CCN) concentrations is crucial for reducing uncertainties in radiative forcing resulting from aerosol–cloud interactions. This study analyses two novel, independent, open-source CCN datasets derived spaceborne Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements and Copernicus Atmosphere Monitoring Service (CAMS) reanalysis examines the spatio-temporal variability of pertinent to liquid clouds. The results reveal consistent large-scale patterns both CALIOP CAMS datasets, although values are approximately 79 % higher than those CAMS. Comparisons existing literature demonstrate that these effectively bound regionally observed concentrations, typically representing upper lower bound. Monthly annual variations obtained largely agree over Northern Hemisphere align previously reported variations. However, inconsistencies emerge pristine oceans, particularly Southern Hemisphere, where show not only opposing seasonal changes but also contrasting trends. Seasonal cycles regions well represented CAMS, previous situ observations, while trends seems be better captured by CALIOP. A comparative droplet suggests dust-influenced maritime environments primary limit our current understanding CCN–cloud relationships. Long-term observations improving advancing

Language: Английский

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Marine Boundary Layer Cloud Condensation Nuclei Bias Over the Southern Ocean: Comparisons Between the Community Atmosphere Model 6 and Field Observations

Journal of Geophysical Research Atmospheres, Journal Year: 2025, Volume and Issue: 130(8)

Published: April 19, 2025

Abstract Marine boundary layer (MBL) clouds play a crucial role in regulating radiative balance the atmosphere. Previous studies identified that MBL cloud droplet number concentration (Nd) is underestimated by factor of 2 over summertime Southern Ocean (SO) close to Antarctic coast many models. Here, comparisons between condensation nuclei (CCN) observations from field campaigns during 2017–2018 Austral summer Australasian sector SO and simulated CCN Community Atmospheric Model 6 (CAM6) are presented. Modeled (N ) underestimated, 100% at latitudes south 55°S with N bias (a) largest Plateau summer, implying biased type has seasonal latitudinal variation and, (b) three times larger sea ice than open water, spray better compared secondary CCN. Assessments aerosol size distributions indicate an underestimation accumulation‐mode‐aerosols (Ac) diameters 70 nm < D 100 nm. supersaturation spectra observed had lower hygroscopicity CCN, differences chemical composition. With aerosols including sulfate being less hygroscopic salt activation ratio derived using bulk kappa Abdul‐Razzak function leads critical 62°S. The biases reported here highlight important shortfalls can be well‐documented d Earth System Models, key feature uncertainty pre‐industrial conditions.

Language: Английский

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MODIS Aerosol and Low‐Cloud Retrievals: Orographic Effects in the Wake of Macquarie Island

Earth and Space Science, Journal Year: 2025, Volume and Issue: 12(5)

Published: April 30, 2025

Abstract Visible/infrared imagery from passive satellites is commonly relied upon to study low cloud microphysics over oceanic regions, including for the Southern Ocean (SO), but relatively little validation has been undertaken SO. In this article, we compare low‐cloud effective radius ( r e ), droplet number concentration N d ) and liquid water path (LWP) retrievals NASA Moderate Imaging Spectroradiometer (MODIS) with surface measurements collected during Macquarie Island Cloud Radiation Experiment (MICRE). MODIS 3.7‐μm band show bias moderately good correlation relative MICRE liquid‐phase clouds when restricted Solar Zenith Angles <65° on spatial scales of 50–100 km. However, overall in 3.7 partly results cancellation errors: overestimated non‐to‐lightly precipitating clouds, underestimated heavier drizzling by ∼1–1.5 μm. 1.6‐μm 2.1‐μm are biased high. may likewise be slightly under‐ or depending concentration, there insufficient data provide confidence result. Interestingly, a composite 2002 2020 distinct region enhanced cover (and lower wake associated orographic formation. aerosol optical depth (AOD) Angstrom Exponent (AE) upwind downwind island do not differ significantly. Comparison suggests that Collection 6 AOD reasonable, while AE problematically large.

Language: Английский

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Simulating Mixed‐Phase Clouds Over Coastal Antarctica During a Significant Snowfall Event in a High‐Resolution Regional Model

Journal of Geophysical Research Atmospheres, Journal Year: 2025, Volume and Issue: 130(10)

Published: May 13, 2025

Abstract Global climate models and reanalysis products have revealed large, persistent downwelling shortwave radiation biases over the Southern Ocean coastal Antarctica, likely caused by incapability of to accurately simulate frequent low‐level mixed‐phase clouds in these regions. In this study, we use ground‐based observations collected at Davis, Antarctica during Precipitation Land The field campaign austral summer 2019 assess capability high‐resolution regional Unified Model (UM) reproduce precipitating off Antarctica. We test new UM RAL3 (Regional Atmosphere 3) configuration with double‐moment Cloud AeroSol Interacting Microphysics scheme bimodal cloud fraction scheme, running spatial resolution 1.5‐km. compare it previous RA2M a single‐moment microphysics unimodal scheme. exhibits marginally degraded meteorological conditions relative compared observations. For properties, can generally phase, vertical structure timing events sublimation precipitation periods. Nevertheless, overestimated ice water path potentially underestimated liquid (LWP) contribute positive surface negative longwave biases. simulates more LWP, though suggest for wrong reasons due its nucleating parameterization. Our results that combined parameterizations, while having reduced performance some respects, has large potential better represent mixed phase region.

Language: Английский

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Impacts of ship emissions and sea-land breeze on urban air quality using chemical characterization, source contribution and dispersion model simulation of PM2.5 at Asian seaport

Environmental Pollution, Journal Year: 2024, Volume and Issue: 347, P. 123663 - 123663

Published: Feb. 28, 2024

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62°S Witnesses the Transition of Boundary Layer Marine Aerosol Pattern Over the Southern Ocean (50°S–68°S, 63°E–150°E) During the Spring and Summer: Results From MARCUS (I)

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(9)

Published: May 6, 2024

Abstract The Atmospheric Radiation Measurement Mobile Facility‐2 was installed onboard the research vessel Aurora Australis to measure aerosol properties during 2017–2018 of Aerosols, Radiation, and CloUds over pristine Southern ocean (MARCUS) Experiment, providing unique data on aerosols latitudinal seasonal variation, including south 60°S where previous observations are scarce. Data from a Cloud Condensation Nuclei (CCN) counter Ultra‐High‐Sensitivity Aerosol Spectrometer show that both number concentration ( N CCN ) size distribution CCN‐active aerosols, with diameters (D) between 60 nm < D 1,000 different North Ocean (NSO) (50°S–60°S) South (SSO) (62°S–68°S). average NSO at 0.2% 0.5% supersaturation were 28% 49% less than SSO. This increase SSO is caused by 200 nm, consistent calculations Scattering Angstrom Exponents derived nephelometer. hygroscopicity growth factor measured Hygroscopic Tandem Differential Mobility Analyzer stayed close 1.41 for 50 250 SSO, but increased 1.30 1.67 NSO, indicating chemical compositions. Both Ice Nucleating Particles (INPs) showed stronger variation season latitude. heat‐labile presumably proteinacous INPs suggests an ice nucleating‐active microbes in summer.

Language: Английский

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Addressing the Urgent Need for Direct Climate Cooling: Rationale and Options

Oxford Open Climate Change, Journal Year: 2024, Volume and Issue: 4(1)

Published: Jan. 1, 2024

Abstract Emissions reduction and removal are not proceeding at a pace that will limit global average warming to less than the Paris Agreement targets of 1.5°C or 2.0°C. Accelerating is indicated by record high 2023–2024 monthly temperatures annual 2023 mean surface around above pre-industrial levels. Only direct climate cooling has potential avert continued temperature rise in near term moderate least some projected change disruption including extreme weather, sea level rise, loss ice, glacier permafrost melting, coral reef die-off. Strategically deployed scale, starting term, several measures have reduce reverse warming. Others can exert local regional influences. The world needs an approach extends beyond sole reliance on emission reductions removal. We propose (i) researching, field testing deploying one more large-scale influence(s) perhaps initially polar regions applying also support adaptation, (ii) accelerating emissions with early prioritization short-lived drivers, (iii) large scale carbon draw down legacy greenhouse gas. authors make no attempt determine what mix optimal. That depend modeling experimentation. properly researched emergency “tourniquets,” near-term our “bleeding” Earth we slow then ongoing increasingly severe 21st Century.

Language: Английский

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