Diverse Dispersion Effects and Parameterization of Relative Dispersion in Urban Fog in Eastern China

Journal of Geophysical Research Atmospheres, Journal Year: 2023, Volume and Issue: 128(6)

Published: March 14, 2023

Abstract Understanding cloud droplet relative dispersion is critical for mitigating the confounding effect of aerosol‐cloud interactions in simulation global climatic patterns. Diverse effects, meaning that correlation between ( ε ) and fog number concentration N f changes from positive to negative as increases at a fixed liquid water content LWC condition, were found urban observed during winters 2017 2018 Nanjing, China. The dominant microphysical processes driving diverse effects be activation, condensation, deactivation, evaporation, sedimentation. first bin (diameter range 2–4 μm) strength volume‐mean diameter D v classifying are 0.3–0.4 10–12 μm, respectively. mean offset DO was −27.6% weakening Twomey 27.5% enhancing it. Assuming Gamma distribution size distribution, significantly underestimated < 0. Based on measured nonmonotonic relationship , we establish parameterization using Nelder function, which can applied effects. deviation diagnosing less than 10% > 0 50% These results could shed new light understanding help reduce uncertainties interactions.

Language: Английский

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Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition

Journal of Geophysical Research Atmospheres, Journal Year: 2022, Volume and Issue: 127(11)

Published: May 25, 2022

Detailed knowledge of the physical and chemical properties sources particles that form clouds is especially important in pristine areas like Arctic, where particle concentrations are often low observations sparse. Here, we present situ cloud aerosol measurements from central Arctic Ocean August-September 2018 combined with air parcel source analysis. We provide direct experimental evidence Aitken mode (particles diameters ≲70 nm) significantly contribute to condensation nuclei (CCN) or droplet residuals, after freeze-up sea ice transition toward fall. These were associated spent more time over pack ice, while size distributions dominated by accumulation ≳70 showed a stronger contribution oceanic slightly different regions. This was accompanied changes average composition an increased relative organic material Addition mass due aqueous-phase chemistry during in-cloud processing probably small given fact observed very similar both whole-air residual data. aerosol-cloud interaction valuable insight into origin CCN Ocean.

Language: Английский

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Observational study of relationships between entrainment rate, homogeneity of mixing, and cloud droplet relative dispersion

Atmospheric Research, Journal Year: 2023, Volume and Issue: 293, P. 106900 - 106900

Published: June 29, 2023

Language: Английский

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Microphysics regimes due to haze–cloud interactions: cloud oscillation and cloud collapse

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(6), P. 3785 - 3806

Published: April 1, 2025

Abstract. It is known that aqueous haze particles can be activated into cloud droplets in a supersaturated environment. However, haze–cloud interactions have not been fully explored, partly because are represented most cloud-resolving models. Here, we conduct series of large-eddy simulations (LESs) convection chamber using haze-capable Eulerian-based bin microphysics scheme to explore over wide range aerosol injection rates. Results show the slow regime at low rates, where responds slowly an environmental change and droplet deactivation negligible. The fast moderate quickly important. More interestingly, two more regimes observed high rates due interactions. Cloud oscillation driven by mean supersaturation around critical collapse happens under weaker forcing transfers efficiently, leading significant decrease (collapse) number concentration. One special case haze-only regime. occurs extremely activation inhibited, sedimentation balanced rate. Our results suggest their with should considered, especially polluted conditions.

Language: Английский

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Improved Parameterization of Cloud Droplet Spectral Dispersion Expected to Reduce Uncertainty in Evaluating Aerosol Indirect Effects

Geophysical Research Letters, Journal Year: 2025, Volume and Issue: 52(7)

Published: March 31, 2025

Abstract Relative dispersion ( ε ), as a parameter characterizing droplet spectral shape, exerts considerable impact on cloud radiation and precipitation processes, its accurate parameterization is urgently needed in models. Current parameterizations, which are based number concentration or simply set constants, inadequate to satisfy the demand. This study shows, utilizing in‐situ fog observations from five underlying surface regions (urban, suburban, mountainous, coastal rainforest) of China, that uniformly stably manifests initially increasing then decreasing volume‐mean diameter increases across these regions. Based this relationship, established, exhibits improved predictive capabilities evaluating both albedo effect lifetime effect. The expected enhance simulation accuracy minimize discrepancy between observed simulated precipitation, particularly for weather climate models commonly use double‐moment microphysical schemes.

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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Aircraft Observations of Turbulence in Cloudy and Cloud‐Free Boundary Layers Over the Western North Atlantic Ocean From ACTIVATE and Implications for the Earth System Model Evaluation and Development

Journal of Geophysical Research Atmospheres, Journal Year: 2022, Volume and Issue: 127(19)

Published: Sept. 15, 2022

Abstract This study examines boundary layer turbulence derived from high temporal resolution meteorological measurements 40 research flights over the western North Atlantic Ocean during 2020 deployments of ACTIVATE. Frequency distributions various turbulent quantities reveal stronger winter deployment than in summer and for cloud‐topped cloud‐free layers deployment. Maximum kinetic energy (TKE) is most often within cloud observations summer, whereas it mostly below both seasons by a global model parameterization. Bivariate frequency are consistent with bivariate Gaussian probability distribution functions assumed closure higher‐order turbulence/shallow convection parameterizations used some models. Turbulence simulated Community Atmosphere Model version 6 Energy Exascale Earth System 2 using such not as strong observed, more TKE going into vertical wind perturbations rather zonal suggesting that treatment system models still needs to be further improved.

Language: Английский

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Scaling of Turbulence and Microphysics in a Convection–Cloud Chamber of Varying Height

Journal of Advances in Modeling Earth Systems, Journal Year: 2023, Volume and Issue: 15(2)

Published: Feb. 1, 2023

Abstract The convection–cloud chamber enables measurement of aerosol and cloud microphysics, as well their interactions, within a turbulent environment under steady‐state conditions. Increasing the size chamber, while holding imposed temperature difference constant, leads to increased Rayleigh, Reynolds Nusselt numbers. Large–eddy simulation coupled with bin microphysics model allows influence velocity, time, spatial scales on microphysical properties be explored. Simulations fixed aspect ratio increasing heights H = 1, 2, 4, (for dry conditions only) 8 m are performed. key findings are: Velocity fluctuations scale 1/3 , consistent Deardorff expression for convective implying that turbulence correlation time 2/3 . Temperature other scalar −3/7 Droplet distributions from chambers different sizes can matched by adjusting total injection rate horizontal cross‐sectional area (i.e., 2 constant ratio). Injection aerosols at point versus distributed throughout volume makes no polluted conditions, but lead droplet distribution broadening in clean Cloud growth collision coalescence broader right tail compared condensation alone, this increases magnitude extent monotonically increase height. These results also have implications scaling turbulent, cloudy mixed‐layers atmosphere, such fog layers.

Language: Английский

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Impact of entrainment-mixing and turbulent fluctuations on droplet size distributions in a cumulus cloud: An investigation using Lagrangian microphysics with a sub-grid-scale model

Journal of the Atmospheric Sciences, Journal Year: 2021, Volume and Issue: unknown

Published: July 15, 2021

Abstract Entrainment-mixing and turbulent fluctuations critically impact cloud droplet size distributions (DSDs) in cumulus clouds. This problem is investigated via a new sophisticated modeling framework using the CM1 LES model Lagrangian microphysics scheme – “super-droplet method” (SDM) coupled with sub-grid-scale (SGS) schemes for particle transport supersaturation fluctuations. used to simulate congestus cloud. Average DSDs different regions show broadening from entrainment secondary activation (activation above base). DSD width increases increasing entrainment-induced dilution as expected past work, except most diluted regions. The SGS allows more treatment of compared previous studies. In these simulations, it contributes about 25%of population impacts two contrastingways: narrowing extremely relatively less diluted. contribute significantly an increase condensation growth evaporation. Mixing super-droplets velocity also broadens DSDs. relative dispersion (ratio mean radius) negatively correlates grid-scale vertical updrafts, but positively correlated downdrafts. latter driven by positive grid-mean subsaturated conditions. Finally, sensitivity grid length evaluated. have greater influence increased, they partially compensate reduced resolution.

Language: Английский

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Direct numerical simulation of turbulence and microphysics in the Pi Chamber

Physical Review Fluids, Journal Year: 2022, Volume and Issue: 7(2)

Published: Feb. 4, 2022

Direct numerical simulation is applied to the Pi Chamber experimental facility understand droplet growth and activation in context of moist Rayleigh-B\'enard turbulence. While many bulk features observations are represented well, Lagrangian approach microphysics used gain insight where experiments cannot. Common assumptions regarding activation-deactivation cycle lifetime shown be likely erroneous.

Language: Английский

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