Characterizing Ice Nucleating Particles Over the Southern Ocean Using Simultaneous Aircraft and Ship Observations

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(2)

Published: Jan. 11, 2024

Abstract Supercooled liquid clouds are ubiquitous over the Southern Ocean (SO), even to temperatures below −20°C, and comprise a large fraction of marine boundary layer (MBL) clouds. Earth system models reanalysis products have struggled reproduce observed cloud phase distribution occurrence ice in region. Recent simulations found microphysical representation nucleation growth has impact on these properties, however, measurements SO nucleating particles (INPs) validate sparse. This study presents INPs from simultaneous aircraft ship campaigns conducted austral summer 2018, which include first situ observations above Our results confirm recent that INP concentrations uniformly lower than made late 1960s. While similar, higher efficiency supports model dominant composition varies with height. Model parameterizations based solely aerosol properties capture mean relationship between concentration temperature but not variability, is likely related only modest correlations environmental or metrics. Including wind speed addition activation parameterization reduces bias does explain range concentrations. Direct indirect inference size suggests MBL INPs, at least during Austral summer, dominated by diameters smaller 500 nm.

Language: Английский

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Predicting atmospheric background number concentration of ice-nucleating particles in the Arctic

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(21), P. 14441 - 14454

Published: Nov. 11, 2022

Abstract. Mixed-phase clouds (MPCs) can have a net warming or cooling radiative effect on Earth's climate influenced by the phase and concentration of cloud particles. They received considerable attention due to high spatial coverage occurrence frequency in Arctic. To initiate ice formation MPCs at temperatures above −38 ∘C, ice-nucleating particles (INPs) are required, which therefore important implications properties altering ice-to-liquid ratio hydrometeors. As result, constraining ambient INP concentrations could promote accurate representation microphysical processes reduce uncertainties estimating cloud-phase-related feedback models. Currently, parameterizations lacking for remote Arctic environments. Here we present number their variability measured Ny-Ålesund (Svalbard) between 0 −30 ∘C. No distinguishable seasonal difference was observed from 12 weeks field measurements during October November 2019 March April 2020. Compared existing studies, absence is not surprising, as most differences reported summer versus winter time concentrations. In addition, correlating aerosol physical successful. Therefore, propose lognormal-distribution-based parameterization predict solely function temperature, specifically transition seasons autumn spring fill data gap literature pertaining these seasons. practice, parameterized variables allow (i) prediction likely (ii) retrieval governing distribution given

Language: Английский

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Untangling the influence of Antarctic and Southern Ocean life on clouds

Elementa Science of the Anthropocene, Journal Year: 2023, Volume and Issue: 11(1)

Published: Jan. 1, 2023

Polar environments are among the fastest changing regions on planet. It is a crucial time to make significant improvements in our understanding of how ocean and ice biogeochemical processes linked with atmosphere. This especially true over Antarctica Southern Ocean where observations severely limited environment far from anthropogenic influences. In this commentary, we outline major gaps knowledge, emerging research priorities, upcoming opportunities needs. We then give an overview large-scale measurement campaigns planned across next 5 years that will address key issues. Until do this, climate models likely continue exhibit biases simulated energy balance delicate region. Addressing these issues require international interdisciplinary approach which hope foster facilitate ongoing community activities collaborations.

Language: Английский

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Circular polarization in atmospheric aerosols

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(20), P. 13581 - 13605

Published: Oct. 20, 2022

Abstract. Recent technological advances have demonstrated the feasibility of deploying spaceborne optical detectors with full polarimetric capabilities. The measurement all four Stokes coefficients opens significant new opportunities for atmospheric aerosol studies and applications. While considerable amounts attention been dedicated to sensors sensitivity total intensity linear polarization (represented by I, U, Q), there has less additional information brought measuring circular (coefficient V). This report fills this gap in knowledge providing an overview sources atmosphere discusses possible remote sensing signatures. In paper, circularly polarized radiation that results from interaction incident unpolarized is considered three physical settings: activity originating biogenic aerosols, alignment non-spherical particles presence electrical fields (such as dust, smoke, volcanic ash), multiple scattering effects. Observational theoretical evidence of, settings conditions for, non-zero generated are here gathered discussed. addition, novel radiative transfer simulations shown illustrate notable spectral other features where may provide possibly independent polarization-only observations. Current techniques detection composition (also referred type) space limited information. Remote identification aerosols such ash, dust can only be accomplished some degree confidence moderate high concentrations. When same found at lower concentrations (but still enough importance air quality cloud formation), these methods often produce ambiguous results. rarely utilized, we explore its value improved determination composition. study presented a goal perspective on overlooked property trigger interest further exploration subject.

Language: Английский

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A Coupled Evaluation of Operational MODIS and Model Aerosol Products for Maritime Environments Using Sun Photometry: Evaluation of the Fine and Coarse Mode

Remote Sensing, Journal Year: 2022, Volume and Issue: 14(13), P. 2978 - 2978

Published: June 22, 2022

Although satellite retrievals and data assimilation have progressed to where there is a good skill for monitoring maritime Aerosol Optical Depth (AOD), remains uncertainty in achieving further degrees of freedom, such as distinguishing fine coarse mode dominated species environments (e.g., sea salt dust versus terrestrial anthropogenic emissions, biomass burning, secondary production). For the years 2016 through 2019, we performed an analysis 550 nm total AOD550, AOD (FAOD550; also known FM literature), (CAOD550), fraction (η550) between Moderate Resolution Spectral Imaging Radiometer (MODIS) V6.1 MOD/MYD04 dark target aerosol International Cooperative Prediction (ICAP) core four multi-model consensus (C4C) analyses/short term forecasts that assimilate MODIS AOD550. Differences were adjudicated by global shipboard Maritime Network (MAN) selected island AERONET sun photometer observations with application spectral deconvolution algorithm (SDA). Through series conditional regional analyses, found divergence included regions influence latitudinal dependencies remote oceans. Notably, C4C its members, while having correlations overall, persistent +0.04 +0.02 biases relative MAN typical AOD550 values (84th% < 0.28), underestimating significant events thereafter. Second, high are largely associated attribution satellites models alike. Thus, both members systematically overestimating FAOD550 but perform better characterizing CAOD550. Third, MODIS, findings consistent previous reports bias retrieved Ångström Exponent, diagnosed optical model cloud masking likely causal factors bias, whereas C4C, it from overproduction perhaps numerical diffusion. Fourth, no wind-speed-dependent surface winds <12 m s−1, AOD550s overestimate CAOD550 FAOD550, respectively, wind speeds above 12 m/s. Finally, sampling inherent MAN, well other circumstantial evidence, suggests even larger than what was here. We conclude discussion on how products their own strengths challenges given climate discuss needed research.

Language: Английский

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Long-term variability in immersion-mode marine ice-nucleating particles from climate model simulations and observations

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(10), P. 5735 - 5762

Published: May 23, 2023

Abstract. Ice-nucleating particles (INPs) in the Southern Ocean (SO) atmosphere have significant impacts on cloud radiative and microphysical properties. Yet, INP prediction skill climate models remains poorly understood, part because of lack long-term measurements. Here we show, for first time, how model-simulated concentrations compare with year-round measurements during Macquarie Island Cloud Radiation Experiment (MICRE) campaign from 2017–2018. We simulate immersion-mode using Energy Exascale Earth System Model version 1 (E3SMv1) by combining simulated aerosols recently developed deterministic parameterizations native classical nucleation theory (CNT) mineral dust E3SMv1. Because MICRE did not collect aerosol super-micron particles, which are more effective ice nucleators, evaluate model's fields at other high-latitude sites situ observations sea spray aerosol. find that model underestimates overestimates to 2 orders magnitude most Hemisphere. next predicted INPs collected filter samples (typically or 3 d) processed offline Colorado State University spectrometer (IS) immersion freezing mode. when both used, within a factor 10 observed than 60 % time summer. Our results also indicate E3SM's current treatment SO is impacted compensating biases – an underprediction amount was compensated overprediction its effectiveness as INPs. perform idealized droplet experiments quantify implications time-dependent behavior assumed CNT-parameterization observations. E3SM CNT s diagnostic used this study reasonable approximation exact formulation CNT, applied low-INP conditions similar Island. However, linearized formula order places high-INP like Sahara. Overall, our findings suggest it important correct life cycle update parameterizations. errors can considerable properties global models. On comparing against ship-based campaigns, Measurements Aerosols, Radiation, Clouds over (MARCUS) Antarctic Circumnavigation Expedition (ACE), latter significantly higher only regions closer This alludes fact physical, chemical biological processes affecting stimulated island could be partly responsible high campaign. Therefore, improvements simulation required adequately their E3SM. It will helpful include parallel measurement size-resolved composition explore opportunities platforms future field campaigns studying sources remote marine regions.

Language: Английский

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The Association Between Cloud Droplet Number over the Summer Southern Ocean and Air Mass History

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(12)

Published: June 11, 2024

Abstract The cloud properties and governing processes in Southern Ocean marine boundary layer clouds have emerged as a central issue understanding the Earth's climate sensitivity. While our of feedbacks evolved most recent model intercomparison, background simulated summertime are not consistent with measurements due to known biases simulating condensation nuclei concentrations. This paper presents several case studies collected during Capricorn 2 Marcus campaigns held aboard Australian research vessels Austral Summer 2018. Combining surface‐observed cases MODIS data along forward backward air mass trajectories, we demonstrate evolution time. These multi‐year statistics showing that long trajectories masses over Antarctic ice sheet critical creating high droplet number latitude summer Ocean. We speculate secondary aerosol production via oxidation biogenically derived precursor gasses actinic flux region sheets is fundamental maintaining relatively numbers Summer.

Language: Английский

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Organic composition of three different size ranges of aerosol particles over the Southern Ocean

Aerosol Science and Technology, Journal Year: 2020, Volume and Issue: 55(3), P. 268 - 288

Published: Nov. 6, 2020

Very few measurements exist of the composition and contribution to cloud condensation nuclei (CCN) organic mass (OM) at different sizes for particles over Southern Ocean. Airborne shipboard composition, aerosol number size distributions, CCN spectra during Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) provide a comparison contributions three ranges: (1) by scanning transmission X-ray microscope (STXM) with near edge absorption fine structure (NEXAFS) 0.25–1.75 µm diameter, (2) electron microscopy energy dispersive spectroscopy (STEM-EDS) 0.1–0.5 0.5–1µm (3) indirectly comparing particle distributions <0.15 diameter. Organic functional groups from STXM-NEXAFS indicate that majority between 0.25 1.75 diameter detectable components were consistent marine signatures associated sea spray particles, which was also true ice nucleating sampled immersion freezing <−27 °C. Clustering 96 NEXAFS resulted in 5 distinct types related mixtures (four salt-containing one organic-rich type without salt core) accounted 76% including two appear primary include acid are likely secondary sources. STEM analysis indicates mostly sulfate 0.5–1 sodium-based spray. The hygroscopicity most >0.1 providing closure measurements. Particles had kappa values 0.2–0.5, indicating substantial presence OM these sizes. component fraction estimated distribution supersaturation varied <10% 70% This result shows impact on concentrations typical supersaturations SO. variable <0.1 µg/m3 smaller than 0.15 but may play role greater 0.3%.Copyright © 2020 American Association Research

Language: Английский

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Natural marine cloud brightening in the Southern Ocean

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(2), P. 1677 - 1685

Published: Feb. 1, 2023

Abstract. The number of cloud droplets per unit volume (Nd) is a fundamentally important property marine boundary layer (MBL) liquid clouds that, at constant water path, exerts considerable controls on albedo. Past work has shown that regional Nd direct correlation to primary productivity (PP) because the role seasonally varying, biogenically derived precursor gases in modulating secondary aerosol properties. These linkages are thought be observable over high-latitude oceans, where strong seasonal variability and meteorology covary mostly pristine environments. Here, we examine from 5 years MODIS Level 2-derived properties broad region summer eastern Southern Ocean adjacent marginal seas. We demonstrate latitudinal, longitudinal temporal gradients strongly correlated with passage air masses high-PP waters concentrated along Antarctic Shelf poleward 60∘ S. find albedo MBL latitudes south S significantly higher than similar path (LWP) north this latitude.

Language: Английский

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Simulating Southern Ocean Aerosol and Ice Nucleating Particles in the Community Earth System Model Version 2

Journal of Geophysical Research Atmospheres, Journal Year: 2023, Volume and Issue: 128(8)

Published: March 21, 2023

Abstract Southern Ocean (SO) low‐level mixed phase clouds have been a long‐standing challenge for Earth system models to accurately represent. While improvements the Community System Model version 2 (CESM2) resulted in increased supercooled liquid SO and improved model radiative biases, simulated CESM2 now contain too little ice. Previous observational studies indicated that marine particles are major contributor cloud heterogeneous ice nucleation, process initiates number of processes govern properties. In this study, we utilize detailed aerosol nucleating particle (INP) measurements from two recent measurement campaigns assess abundance, size distributions, composition INP parameterizations use CESM2. Our results indicate has positive bias surface‐level total surface area at latitudes north 58°S. Measured populations were dominated by INPs present evidence refractory over assumed here be mineral dust INPs. Results highlight critical need distributions order adequately represent their response long‐term changes atmospheric transport patterns land change. We also discuss important cautions limitations applying commonly used parameterization remote regions like pristine SO.

Language: Английский

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