Observations of Clouds, Aerosols, Precipitation, and Surface Radiation over the Southern Ocean: An Overview of CAPRICORN, MARCUS, MICRE, and SOCRATES

Bulletin of the American Meteorological Society, Journal Year: 2020, Volume and Issue: 102(4), P. E894 - E928

Published: Nov. 30, 2020

Abstract Weather and climate models are challenged by uncertainties biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, processes, their interactions. Projects between 2016 2018 used situ probes, radar, lidar, other instruments make comprehensive measurements thermodynamics, surface radiation, cloud condensation nuclei (CCN), ice nucleating particles over the SO cold waters, ubiquitous liquid mixed-phase clouds common this pristine environment. Data including soundings were collected from NSF–NCAR G-V aircraft flying north–south gradients south Tasmania, at Macquarie Island, on R/V Investigator RSV Aurora Australis . Synergistically these data characterize boundary layer free troposphere environmental properties, represent most type available oceanic polar front, sector cyclones, across seasons. Results show largely environments with numerous small few large aerosols above suggesting new particle formation limited long-range transport continents, high variability CCN droplet concentrations, supercooled water thin, multilayered clouds, often small-scale generating cells near top. These observations demonstrate how properties depend while highlighting importance dynamics turbulence likely drive heterogeneity phase. Satellite retrievals confirmed low responsible for radiation biases. The combination is examining meteorology couple control energy budgets.

Language: Английский

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Cloud‐Nucleating Particles Over the Southern Ocean in a Changing Climate

Earth s Future, Journal Year: 2021, Volume and Issue: 9(3)

Published: Feb. 23, 2021

Abstract Stratocumulus clouds over the Southern Ocean have fewer droplets and are more likely to exist in predominately supercooled phase than at similar temperatures northern oceans. One reason is that this region has few continental anthropogenic sources of cloud‐nucleating particles can form ice. In work, we present an overview aerosol particle types Ocean, including new measurements made below, above region. These others indicate biogenic sulfur‐based >0.1 μm diameter contribute majority cloud condensation nuclei number concentrations summer. Ice nucleating tend organic components, from sea‐spray. Both may increase a warming climate less sea ice, phytoplankton activity, stronger winds near Antarctica. Taken together, become reflective partially counter region's expected albedo decrease due diminishing However, detailed modeling studies needed test hypothesis complexity ocean‐cloud‐climate feedbacks

Language: Английский

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Dilution of Boundary Layer Cloud Condensation Nucleus Concentrations by Free Tropospheric Entrainment During Marine Cold Air Outbreaks

Geophysical Research Letters, Journal Year: 2022, Volume and Issue: 49(11)

Published: May 31, 2022

Abstract Recent aircraft measurements over the northwest Atlantic enable an investigation of how entrainment from free troposphere (FT) impacts cloud condensation nucleus (CCN) concentrations in marine boundary layer (MBL) during cold‐air outbreaks (CAOs), motivated by role CCN mediating transitions closed to open‐cell regimes. Observations compiled eight flights indicate predominantly far lesser FT than MBL. For one flight, a fetch‐dependent MBL‐mean budget is estimates sea‐surface fluxes, air, and hydrometeor collision‐coalescence, based on in‐situ remote‐sensing measurements. Results dominant reducing MBL concentrations, consistent with satellite‐observed trends droplet number concentration upwind CAO cloud‐regime Atlantic. Relatively scant may widely be associated dry intrusions, should accelerate where underlying air CCN‐rich, thereby regional albedo.

Language: Английский

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The biogeochemistry of marine dimethylsulfide

Nature Reviews Earth & Environment, Journal Year: 2023, Volume and Issue: 4(6), P. 361 - 376

Published: June 7, 2023

Language: Английский

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Direct sulfuric acid formation from the gas-phase oxidation of reduced-sulfur compounds

Nature Communications, Journal Year: 2023, Volume and Issue: 14(1)

Published: Aug. 10, 2023

Sulfuric acid represents a fundamental precursor for new nanometre-sized atmospheric aerosol particles. These particles, after subsequent growth, may influence Earth´s radiative forcing directly, or indirectly through affecting the microphysical and properties of clouds. Currently considered formation routes yielding sulfuric in atmosphere are gas-phase oxidation SO2 initiated by OH radicals Criegee intermediates, latter being little relevance. Here we report observation immediate production from reaction emitted organic reduced-sulfur compounds, which was speculated about literature decades. Key intermediates methylsulfonyl radical, CH3SO2, and, even more interestingly, its corresponding peroxy compound, CH3SO2OO. Results modelling pristine marine conditions show that compounds could be responsible up to ∼50% formed these areas. Our findings provide complete understanding oxidation.

Language: Английский

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Atmospheric new particle formation from the CERN CLOUD experiment

Nature Geoscience, Journal Year: 2023, Volume and Issue: 16(11), P. 948 - 957

Published: Nov. 1, 2023

Language: Английский

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Low‐Volatility Vapors and New Particle Formation Over the Southern Ocean During the Antarctic Circumnavigation Expedition

Journal of Geophysical Research Atmospheres, Journal Year: 2021, Volume and Issue: 126(22)

Published: Oct. 16, 2021

Abstract During summer, the Southern Ocean is largely unaffected by anthropogenic emissions, which makes this region an ideal place to investigate marine natural aerosol sources and processes. A better understanding of key constrain preindustrial state reduce radiative forcing uncertainty in global climate models. We report concentrations gaseous sulfuric acid, iodic methanesulfonic acid (MSA) together with a characterization new particle formation (NPF) events over large stretch Ocean. Measurements were conducted on board Russian icebreaker Akademik Tryoshnikov from January March 2017. Iodic characterized particular diurnal cycle reduced concentration around noon, suggesting lower yield when solar irradiance higher. Gaseous MSA does not have measured gas condensed phase are compatible species being primarily produced via heterogeneous oxidation dimethyl sulfide subsequent partitioning into phase. also found that NPF boundary layer mainly driven but it occurred very rarely vast geographical area probed did contribute cloud condensation nuclei budget directly observable manner. Despite near absence layer, Aitken mode particles frequently measured, supporting hypothesis free tropospheric source. participate nucleation, however, may growth aqueous

Language: Английский

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Coalescence Scavenging Drives Droplet Number Concentration in Southern Ocean Low Clouds

Geophysical Research Letters, Journal Year: 2022, Volume and Issue: 49(7)

Published: March 27, 2022

Abstract Cloud droplet number concentration ( N d ) is a key microphysical property that largely controlled by the balance between sources and sinks of aerosols serve as cloud condensation nuclei (CCN). Despite being sink CCN, impact coalescence scavenging on Southern Ocean (SO) poorly known. We apply simple source‐and‐sink budget model based parameterizations to austral summer aircraft observations test behavior examine relative influence processes determine in SO stratocumulus clouds. The predicts with little bias correlation coefficient ∼0.7 compared observations. Coalescence found be an important CCN both liquid mixed‐phase precipitating reduces predicted much 90% depending precipitation rate. free tropospheric aerosol source controls more strongly than surface during summer.

Language: Английский

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Seasonal updraft speeds change cloud droplet number concentrations in low-level clouds over the western North Atlantic

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(12), P. 8299 - 8319

Published: June 28, 2022

Abstract. To determine the impact of dynamic and aerosol processes on marine low clouds, we examine seasonal updraft speed w cloud condensation nuclei concentration at 0.43 % supersaturation (NCCN0.43%) droplet number (NC) low-level clouds over western North Atlantic Ocean. Aerosol properties were measured with instruments board NASA LaRC Falcon HU-25 during ACTIVATE (Aerosol Cloud meTeorology Interactions oVer ATlantic Experiment) mission in summer (August) winter (February–March) 2020. The data are grouped into different NCCN0.43% loadings, density functions NC near bases compared. For updrafts (w < 1.3 m s−1), is mainly limited by additionally aerosols. At larger > 3 impacted population, while clean conditions nucleation aerosol-limited, for high it influenced aerosols updraft. size distribution shows a bimodal environments, which transforms to unimodal due chemical physical processes, whereas distributions prevail summer, significant difference their composition. increase accompanied an organic sulfate compounds both seasons. We demonstrate that can be explained activation through upwards processed air masses varying fractions activated highly depends thus between seasons, affects within season. Our results quantify influence used improve representation models.

Language: Английский

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The Role of Mesoscale Cloud Morphology in the Shortwave Cloud Feedback

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(2)

Published: Jan. 18, 2023

Abstract A supervised neural network algorithm is used to categorize near‐global satellite retrievals into three mesoscale cellular convective (MCC) cloud morphology patterns. At constant amount, patterns differ in brightness associated with the amount of optically thin features. Environmentally driven transitions from closed MCC other patterns, typically accompanied by more features, are as a framework quantify contribution optical depth component shortwave feedback. marine heat wave an out‐of‐sample test occurrence predictions. Morphology shifts between 65°S and 65°N under projected environmental changes (i.e., abrupt quadrupling CO 2 ) assuming cover contributes 0.04 0.07 W m −2 K −1 (aggregate 0.06) global mean

Language: Английский

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