Confronting the Challenge of Modeling Cloud and Precipitation Microphysics

Journal of Advances in Modeling Earth Systems, Год журнала: 2020, Номер 12(8)

Опубликована: Май 11, 2020

In the atmosphere, microphysics refers to microscale processes that affect cloud and precipitation particles is a key linkage among various components of Earth's atmospheric water energy cycles. The representation microphysical in models continues pose major challenge leading uncertainty numerical weather forecasts climate simulations. this paper, problem treating divided into two parts: (i) how represent population particles, given impossibility simulating all individually within cloud, (ii) uncertainties process rates owing fundamental gaps knowledge physics. recently developed Lagrangian particle-based method advocated as way address several conceptual practical challenges representing particle populations using traditional bulk bin parameterization schemes. For addressing critical physics knowledge, sustained investment for observational advances from laboratory experiments, new probe development, next-generation instruments space needed. Greater emphasis on work, which has apparently declined over past decades relative other areas research, argued be an essential ingredient improving process-level understanding. More systematic use natural observations constrain schemes also advocated. Because it generally difficult quantify individual these directly, presents inverse can viewed standpoint Bayesian statistics. Following idea, probabilistic framework proposed combines elements statistical physical modeling. Besides providing rigorous constraint schemes, there added benefit quantifying systematically. Finally, broader hierarchical approach accelerate improvements leveraging described paper related modeling (using schemes), experimentation, observations, methods.

Язык: Английский

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Opportunistic experiments to constrain aerosol effective radiative forcing

Atmospheric chemistry and physics, Год журнала: 2022, Номер 22(1), С. 641 - 674

Опубликована: Янв. 17, 2022

Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due human activities. The nonlinearity cloud-state changes aerosol perturbations make it challenging attribute causality in observed relationships forcing. Using correlations infer can when meteorological variability also drives both and cloud independently. Natural anthropogenic from well-defined sources provide "opportunistic experiments" (also known as natural experiments) investigate ACI cases where may more confidently inferred. These cover a wide range locations spatiotemporal scales, including point such volcanic eruptions or industrial sources, plumes biomass burning forest fires, tracks individual ships shipping corridors. We review different experimental conditions conduct synthesis available satellite datasets field campaigns place these opportunistic experiments on common footing, facilitating new insights clearer understanding key uncertainties Cloud albedo strongly sensitive background conditions. Strong liquid water path increases largely ruled out by averaging across experiments. Opportunistic have significantly improved process-level ACI, but remains unclear how reliably found scaled global level, thus demonstrating need for deeper investigation order improve assessments climate change.

Язык: Английский

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

Journal of Geophysical Research Atmospheres, Год журнала: 2023, Номер 128(6)

Опубликована: Март 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.

Язык: Английский

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Broadening of Cloud Droplet Spectra through Eddy Hopping: Turbulent Adiabatic Parcel Simulations

Journal of the Atmospheric Sciences, Год журнала: 2017, Номер 74(5), С. 1485 - 1493

Опубликована: Март 27, 2017

Abstract This paper investigates spectral broadening of droplet size distributions through a mechanism referred to as the eddy hopping. The key idea, suggested quarter century ago, is that droplets arriving at given location within turbulent cloud follow different trajectories and thus experience growth histories this leads significant broadening. In study, adiabatic parcel model with superdroplets used contrast without turbulence. Turbulence inside described by two parameters: (i) dissipation rate kinetic energy ε (ii) linear extent L. As expected, an turbulence produces extremely narrow spectra. parcel, stochastic scheme account for vertical velocity fluctuations lead local supersaturation each superdroplet. These mimic impact hopping eddies in natural cloud. For L smaller than few meters, noticeable possible only strong turbulence—say, &gt; 100 cm2 s−3. typical grid lengths large-eddy simulation (LES) models (say, between 10 m), even relatively modest intensities. increases both ε. representation developed can be included straightforward way subgrid-scale Lagrangian LES may acceleration simulated rain development collision–coalescence.

Язык: Английский

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DNS and LES for Simulating Stratocumulus: Better Together

Journal of Advances in Modeling Earth Systems, Год журнала: 2018, Номер 10(7), С. 1421 - 1438

Опубликована: Июнь 12, 2018

Abstract We argue that combining direct numerical simulation (DNS) with large‐eddy (LES) and field studies could accelerate current lines of stratocumulus research. LES allows for a faster more holistic study the parameter space, but is sensitive to details its formulation because energetics are tied unresolved processes in cloud top region. One way assess this sensitivity through studies. Another DNS. In particular, DNS can be used test hypothesis LES, even an inadequate representation physics entrainment, properly quantifies cloud‐topped boundary layers changing environmental conditions. support argument by contrasting theoretical aspects both techniques, presenting first results stratocumulus‐topped layer discussing their convergence toward Reynolds number similarity, showing consistency measurements.

Язык: Английский

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Broadening of Cloud Droplet Spectra through Eddy Hopping: Turbulent Entraining Parcel Simulations

Journal of the Atmospheric Sciences, Год журнала: 2018, Номер 75(10), С. 3365 - 3379

Опубликована: Авг. 1, 2018

This paper discusses the effects of cloud turbulence, turbulent entrainment, and entrained condensation nuclei (CCN) activation on evolution droplet size spectrum. We simulate an ensemble idealized parcels that are subject to entrainment events modeled as a random process. Entrainment events, subsequent mixing inside parcel, supersaturation fluctuations, resulting stochastic growth by simulated using Monte Carlo scheme. Quantities characterizing turbulence intensity, rate, CCN concentration, mean fraction environmental air in event all specified independent external parameters. Cloud microphysics is described applying Lagrangian particles, so-called superdroplets. These either unactivated or droplets grow from activated CCN. The model accounts for addition into entraining eddies at edge. Turbulent dry with cloudy classical linear relaxation model. show plays important role aiding activate, thus broadening distribution. findings consistent previous large-eddy simulations (LESs) consider impact variable histories spectra small cumuli. scheme developed this work ready be used subgrid-scale LESs natural clouds.

Язык: Английский

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Extensive Soot Compaction by Cloud Processing from Laboratory and Field Observations

Scientific Reports, Год журнала: 2019, Номер 9(1)

Опубликована: Авг. 14, 2019

Abstract Soot particles form during combustion of carbonaceous materials and impact climate air quality. When freshly emitted, they are typically fractal-like aggregates. After atmospheric aging, can act as cloud condensation nuclei, water or evaporation restructure them to more compact aggregates, affecting their optical, aerodynamic, surface properties. Here we survey the morphology ambient soot from various locations different environmental aging conditions. We used electron microscopy show extensive compaction after processing. further performed laboratory experiments simulate processing under controlled find that sampled evaporating droplets, significantly than emitted interstitial soot, confirming processing, not just exposure high humidity, compacts soot. Our findings have implications for how radiative, surface, aerodynamic properties, fate represented in numerical models.

Язык: Английский

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The role of turbulent fluctuations in aerosol activation and cloud formation

Proceedings of the National Academy of Sciences, Год журнала: 2020, Номер 117(29), С. 16831 - 16838

Опубликована: Июль 8, 2020

Significance Formation of cloud droplets is a threshold phenomenon; form only when the local relative humidity (RH) exceeds critical value which depends on size and chemical composition preexisting aerosol particles serve as seeds for droplets. In traditional view this process, average RH considered. However, clouds are ubiquitously turbulent, meaning they characterized not by single humidity, but distribution. We show, with laboratory experiments theory, that formation occurs in three regimes, relationship between distribution environment value. Our results show fluctuations must be considered, well average.

Язык: Английский

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Environmental effects on aerosol–cloud interaction in non-precipitating marine boundary layer (MBL) clouds over the eastern North Atlantic

Atmospheric chemistry and physics, Год журнала: 2022, Номер 22(1), С. 335 - 354

Опубликована: Янв. 10, 2022

Abstract. Over the eastern North Atlantic (ENA) ocean, a total of 20 non-precipitating single-layer marine boundary layer (MBL) stratus and stratocumulus cloud cases are selected to investigate impacts environmental variables on aerosol–cloud interaction (ACIr) using ground-based measurements from Department Energy Atmospheric Radiation Measurement (ARM) facility at ENA site during 2016–2018. The ACIr represents relative change in droplet effective radius re with respect condensation nuclei (CCN) number concentration 0.2 % supersaturation (NCCN,0.2 %) stratified water vapor environment. values vary −0.01 0.22 increasing sub-cloud precipitable (PWVBL) conditions, indicating that is more sensitive CCN loading under sufficient supply, owing combined effect enhanced condensational growth coalescence processes associated higher Nc PWVBL. principal component analysis shows most pronounced pattern co-variations MBL conditions characterized by vertical turbulence kinetic energy (TKEw), decoupling index (Di), effects emerge after data into different TKEw regimes. values, both lower PWVBL than double low-TKEw high-TKEw regime. This can be explained fact stronger maintains well-mixed MBL, strengthening connection between microphysical properties below-cloud moisture sources. With low loading, active process broadens size spectra consequently results an enlargement re. activation induced effectively decrease re, which jointly presents as increased ACIr. study examines importance assessments provides observational constraints future model evaluations interactions.

Язык: Английский

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

Atmospheric chemistry and physics, Год журнала: 2025, Номер 25(6), С. 3785 - 3806

Опубликована: Апрель 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.

Язык: Английский

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