Indirect Impact of Atmospheric Aerosols in Idealized Simulations of Convective–Radiative Quasi Equilibrium

2006 ◽  
Vol 19 (18) ◽  
pp. 4664-4682 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Solar Energy ◽  
Indirect Effect ◽  
Cloud Microphysics ◽  
Effective Radius ◽  
Future Research ◽  
Quasi Equilibrium ◽  
Shallow Convection ◽  
Cloud Droplets ◽  
The Mean ◽  
The Impact

Abstract This paper discusses a cloud-resolving modeling study concerning the impact of warm-rain microphysics on convective–radiative quasi equilibrium with fixed surface characteristics and prescribed solar input, both mimicking the mean conditions on earth. Two limits of the concentration of cloud droplets, either 100 cm−3 (referred to as “pristine”) or 1000 cm−3 (referred to as “polluted”), are considered. In addition, three formulations of the effective radius of water droplets in diluted cloudy volumes are used, corresponding to the homogeneous, intermediate, and extremely inhomogeneous mixing scenarios. The assumed concentration of cloud droplets, together with the assumed mixing scenario, affects the local value of the effective radius of cloud droplets (the first indirect aerosol effect, also known as the Twomey effect) and the transfer of cloud water into drizzle and rain, which can affect the mean cloudiness and the hydrologic cycle (the second indirect effect). The convective–radiative quasi equilibrium mimics the estimates of globally and annually averaged water and energy fluxes across the earth’s atmosphere to within less than 10 W m−2. As on earth, the model cloudiness is dominated by shallow convection. It is found that the impact of warm microphysics is dominated by the first indirect effect, whereas the second indirect effect has a smaller impact. The assumed droplet concentration and mixing scenario impact the mean “planetary” albedo and, thus, the amount of solar energy reaching the surface, with all other components of atmospheric energy and water budgets virtually the same in all simulations. The weak second indirect effect highlights the difference between the impact of cloud microphysics on a single cloud and the impact on an ensemble of clouds, with only the latter including the feedbacks between clouds and their environment. The formulation of the effective radius in the diluted cloudy volumes turns out to be of critical importance, with the amount of solar energy reaching the surface being the same in the pristine case assuming the homogeneous mixing scenario and in the polluted case with the extremely inhomogeneous mixing. This result emphasizes the essential role of poorly understood microphysical transformations within diluted convective clouds, which strongly impact the magnitude of the first indirect (Twomey) effect. Implications for future research in this area are discussed.

scholarly journals Indirect Impact of Atmospheric Aerosols in Idealized Simulations of Convective–Radiative Quasi Equilibrium. Part II: Double-Moment Microphysics

2011 ◽  
Vol 24 (7) ◽  
pp. 1897-1912 ◽  
Author(s):  
Wojciech W. Grabowski ◽  
Hugh Morrison
Keyword(s):  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Bowen Ratio ◽  
Cloud Microphysics ◽  
Quasi Equilibrium ◽  
Double Moment ◽  
The Mean ◽  
The Difference ◽  
The Impact

Abstract This paper extends the previous cloud-resolving modeling study concerning the impact of cloud microphysics on convective–radiative quasi equilibrium (CRQE) over a surface with fixed characteristics and prescribed solar input, both mimicking the mean conditions on earth. The current study applies sophisticated double-moment warm-rain and ice microphysics schemes, which allow for a significantly more realistic representation of the impact of aerosols on precipitation processes and on the coupling between clouds and radiative transfer. Two contrasting cloud condensation nuclei (CCN) characteristics are assumed, representing pristine and polluted conditions, as well as contrasting representations of the effects of entrainment and mixing on the mean cloud droplet size. In addition, four sets of sensitivity simulations are also performed with changes that provide a reference for the main simulation set. As in the previous study, the CRQE mimics the estimates of globally and annually averaged water and energy fluxes across the earth’s atmosphere. There are some differences from the previous study, however, consistent with the slightly lower water vapor content in the troposphere and significantly reduced lower-tropospheric cloud fraction in current simulations. There is also a significant reduction of the difference between the pristine and polluted cases, from ∼20 to ∼4 W m−2 at the surface from ∼20 to ∼9 W m−2 at the top of the atmosphere (TOA). The difference between the homogeneous and extremely inhomogeneous mixing scenarios, ∼20 W m−2 in the previous study, is reduced to a mere 2 (1) W m−2 at the surface (TOA). An unexpected difference between the previous and current simulations is the lower Bowen ratio of the surface heat flux, the partitioning of the total flux into sensible and latent components. It is shown that most of the change comes from the difference in the representation of rain evaporation in the subcloud layer in the single- and double-moment microphysics schemes. The difference affects the mean air temperature and humidity near the surface, and thus the Bowen ratio. The differences between the various simulations are discussed, contrasting the process-level approach with the impact of cloud microphysics on the quasi-equilibrium state with a more appropriate system dynamics approach. The key distinction is that the latter includes the interactions among all the processes in the modeled system.

scholarly journals Extracting Microphysical Impacts in Large-Eddy Simulations of Shallow Convection

2014 ◽  
Vol 71 (12) ◽  
pp. 4493-4499 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Traditional Approach ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Natural Variability ◽  
Large Eddy Simulations ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Large Eddy ◽  
The Mean ◽  
The Impact

Abstract A simple methodology is proposed to extract impacts of cloud microphysics on macrophysical cloud-field properties in large-eddy simulations of shallow convection. These impacts are typically difficult to assess because of natural variability of the simulated cloud field. The idea is to use two sets of thermodynamic variables driven by different microphysical schemes or by a single scheme with different parameters as applied here. The first set is coupled to the dynamics as in the standard model, and the second set is applied diagnostically—that is, driven by the flow but without the feedback on the flow dynamics. Having the two schemes operating in the same flow pattern allows for extracting the impact with high confidence. For illustration, the method is applied to simulations of precipitating shallow convection applying a simple bulk representation of warm-rain processes. Because of natural variability, the traditional approach provides an uncertain estimate of the impact of cloud droplet concentration on the mean cloud-field rainfall even with an ensemble of simulations. In contrast, the impact is well constrained while applying the new methodology. The method can even detect minuscule changes of the mean cloud cover and liquid water path despite their large temporal fluctuations and different evolutions within the ensemble.

scholarly journals Plasma mineral (selenium, zinc or copper) concentrations in the general pregnant population, adjusted for supplement intake, in relation to thyroid function

2020 ◽  
Vol 125 (1) ◽  
pp. 71-78
Author(s):  
Victor Pop ◽  
Johannes Krabbe ◽  
Wolfgang Maret ◽  
Margaret Rayman
Keyword(s):  
Thyroid Function ◽  
Reference Range ◽  
First Trimester ◽  
Future Research ◽  
Thyroid Peroxidase ◽  
Reference Ranges ◽  
Lower Plasma ◽  
The Mean ◽  
The Impact ◽  
Supplement Intake

AbstractThe present study reports on first-trimester reference ranges of plasma mineral Se/Zn/Cu concentration in relation to free thyroxine (FT4), thyrotropin (TSH) and thyroid peroxidase antibodies (TPO-Ab), assessed at 12 weeks’ gestation in 2041 pregnant women, including 544 women not taking supplements containing Se/Zn/Cu. The reference range (2·5th–97·5th percentiles) in these 544 women was 0·72–1·25 µmol/l for Se, 17·15–35·98 µmol/l for Cu and 9·57–16·41 µmol/l for Zn. These women had significantly lower mean plasma Se concentration (0·94 (sd 0·12) µmol/l) than those (n 1479) taking Se/Zn/Cu supplements (1·03 (sd 0·14) µmol/l; P < 0·001), while the mean Cu (26·25 µmol/l) and Zn (12·55 µmol/l) concentrations were almost identical in these sub-groups. Women with hypothyroxinaemia (FT4 below reference range with normal TSH) had significantly lower plasma Zn concentrations than euthyroid women. After adjusting for covariates including supplement intake, plasma Se (negatively), Zn and Cu (positively) concentrations were significantly related to logFT4; Se and Cu (but not Zn) were positively and significantly related to logTSH. Women taking additional Se/Zn/Cu supplements were 1·46 (95 % CI 1·09, 2·04) times less likely to have elevated titres of TPO-Ab at 12 weeks of gestation. We conclude that first-trimester Se reference ranges are influenced by Se-supplement intake, while Cu and Zn ranges are not. Plasma mineral Se/Zn/Cu concentrations are associated with thyroid FT4 and TSH concentrations. Se/Zn/Cu supplement intake affects TPO-Ab status. Future research should focus on the impact of trace mineral status during gestation on thyroid function.

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

2018 ◽  
Vol 75 (10) ◽  
pp. 3365-3379 ◽  
Author(s):  
Gustavo C. Abade ◽  
Wojciech W. Grabowski ◽  
Hanna Pawlowska
Keyword(s):  
Droplet Size ◽  
Turbulent Mixing ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Droplet Growth ◽  
Size Spectrum ◽  
Entrainment Rate ◽  
The Mean ◽  
The Impact

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

scholarly journals Monte Carlo-based subgrid parameterization of vertical velocity and stratiform cloud microphysics in ECHAM5.5-HAM2

2013 ◽  
Vol 13 (2) ◽  
pp. 5477-5507
Author(s):  
J. Tonttila ◽  
P. Räisänen ◽  
H. Järvinen
Keyword(s):  
Monte Carlo ◽  
Vertical Velocity ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Radiative Effects ◽  
Cloud Droplets ◽  
Microphysical Properties ◽  
Cloud Radiative Effects ◽  
Cloud Activation ◽  
The Impact

Abstract. A new method for parameterizing the subgrid variations of vertical velocity and cloud droplet number concentration (CDNC) is presented for GCMs. These parameterizations build on top of existing parameterizations that create stochastic subgrid cloud columns inside the GCM grid-cells, which can be employed by the Monte Carlo independent column approximation approach for radiative transfer. The new model version adds a description for vertical velocity in individual subgrid columns, which can be used to compute cloud activation and the subgrid distribution of the number of cloud droplets explicitly. This provides a consistent way for simulating the cloud radiative effects with two-moment cloud microphysical properties defined in subgrid-scale. The primary impact of the new parameterizations is to decrease the CDNC over polluted continents, while over the oceans the impact is smaller. This promotes changes in the global distribution of the cloud radiative effects and might thus have implications on model estimation of the indirect radiative effect of aerosols.

Lagrangian stochastic microphysics at unresolved scales in turbulent cloud simulations

2020 ◽  
Author(s):  
Gustavo Abade ◽  
Marta Waclawczyk ◽  
Wojciech W. Grabowski ◽  
Hanna Pawlowska
Keyword(s):  
Droplet Size ◽  
Cloud Condensation Nuclei ◽  
Droplet Size Distribution ◽  
Cloud Microphysics ◽  
Cloud Droplets ◽  
Adiabatic Cooling ◽  
Subgrid Scales ◽  
The Mean ◽  
Microphysical Processes ◽  
Droplet Size Distributions

&lt;p&gt;Turbulent clouds are challenging to model and simulate due to uncertainties in microphysical processes occurring at unresolved subgrid scales (SGS). These processes include the transport of cloud particles, supersaturation fluctuations, turbulent mixing, and the resulting stochastic droplet activation and growth by condensation. In this work, we apply two different Lagrangian stochastic schemes to model SGS cloud microphysics. Collision and coalescence of droplets are not considered. Cloud droplets and unactivated cloud condensation nuclei (CCN) are described by Lagrangian particles (superdroplets). The first microphysical scheme directly models the supersaturation fluctuations experienced by each Lagrangian superdroplet as it moves with the air flow. Supersaturation fluctuations are driven by turbulent fluctuations of the droplet vertical velocity through the adiabatic cooling/warming effect. The second, more elaborate scheme uses both temperature and vapor mixing ratio as stochastic attributes attached to each superdroplet. It is based on the probability density function formalism that provides a consistent Eulerian-Lagrangian formulation of scalar transport in a turbulent flow. Both stochastic microphysical schemes are tested in a synthetic turbulent-like cloud flow that mimics a stratocumulus topped boundary layer. It is shown that SGS turbulence plays a key role in broadening the droplet-size distribution towards larger sizes. Also, the feedback on water vapor of stochastically activated droplets buffers the variations of the mean supersaturation driven the resolved transport. This extends the distance over which entrained CNN are activated inside the cloud layer and produces multimodal droplet-size distributions.&lt;/p&gt;

The Strong Impact of Weak Horizontal Convergence on Continental Shallow Convection

2020 ◽  
Vol 77 (9) ◽  
pp. 3119-3137
Author(s):  
Marcin J. Kurowski ◽  
Wojciech W. Grabowski ◽  
Kay Suselj ◽  
João Teixeira
Keyword(s):  
Large Scale ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Small Scale ◽  
Strong Impact ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Strong Response ◽  
The Impact ◽  
Benchmark Solutions

Abstract Idealized large-eddy simulation (LES) is a basic tool for studying three-dimensional turbulence in the planetary boundary layer. LES is capable of providing benchmark solutions for parameterization development efforts. However, real small-scale atmospheric flows develop in heterogeneous and transient environments with locally varying vertical motions inherent to open multiscale interactive dynamical systems. These variations are often too subtle to detect them by state-of-the-art remote and in situ measurements, and are typically excluded from idealized simulations. The present study addresses the impact of weak [i.e., O(10−6) s−1] short-lived low-level large-scale convergence/divergence perturbations on continental shallow convection. The results show a strong response of shallow nonprecipitating convection to the applied weak large-scale dynamical forcing. Evolutions of CAPE, mean liquid water path, and cloud-top heights are significantly affected by the imposed convergence/divergence. In contrast, evolving cloud-base properties, such as the area coverage and mass flux, are only weakly affected. To contrast those impacts with microphysical sensitivity, the baseline simulations are perturbed assuming different observationally based cloud droplet number concentrations and thus different rainfall. For the tested range of microphysical perturbations, the imposed convergence/divergence provides significantly larger impact than changes in the cloud microphysics. Simulation results presented here provide a stringent test for convection parameterizations, especially important for large-scale models progressing toward resolving some nonhydrostatic effects.

scholarly journals Substance Use Among Patients Receiving Out- and Inpatient Dependence Care: a Prospective Norwegian Cohort Study From 2016 to 2020

2021 ◽  
Author(s):  
Jørn Henrik Vold ◽  
Fatemeh Chalabianloo ◽  
Christer F. Aas ◽  
Else-Marie Løberg ◽  
Kjell Arne Johansson ◽  
...  
Keyword(s):  
Substance Use ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Severity Index ◽  
Future Research ◽  
Opioid Agonist ◽  
Low Threshold ◽  
The Mean ◽  
The Impact ◽  
Over Time

Abstract BackgroundContinuous use of amphetamines, alcohol, benzodiazepines, cannabis, cocaine, or opioids contributes to health impairments, increased morbidity, and overdose deaths among patients with substance use disorders (SUDs). This study evaluates the impact of inpatient detoxification, specialized opioid agonist therapy (OAT), and low-threshold municipality care on substance use over time. MethodsWe used data from a cohort of SUD patients in Norway through health assessments of self-reported substance use and sociodemographic and clinical factors. A total of 881 substance use measurements, including type and amount of substances, were assessed from 708 SUD patients in 2016-2020. Substance use for individual and total substances was calculated, creating a substance use severity index (SUSI) ranging from zero (no use) to one (daily use). We defined baseline as the first substance use measurement when the measurements were listed chronologically. Time was defined as years from baseline. We used a linear mixed model to analyze associations between the SUSI and inpatient detoxification, specialized OAT compared with low-threshold municipality care, as well as the factors like injecting substance use, gender, and age, presented with coefficients and 95% confidence intervals (CI).ResultsNeither inpatient detoxification (mean SUSI change: 0.01, -0.03;0.04) nor specialized OAT (0.03, -0.09;0.14) compared with low-threshold municipality care were associated with changes in substance use over time. Patients who were over 60 years of age (mean SUSI difference: -0.06, -0.13;0.00) had a lower SUSI than those under 30 years of age, while patients who injected substances had a higher SUSI than those who did not inject substances (0.18, 0.15;0.20) at baseline. The mean SUSI for the individual substances were 0.50 (standard deviation (SD): 0.38) for cannabis, 0.40 (0.37) for benzodiazepines, 0.33 (0.34) for amphetamines and cocaine, 0.31 (0.29) for alcohol, and 0.22 (0.31) for opioids at baseline. The mean SUSI of all substances was 0.35 (0.20). Conclusion The present study demonstrates that neither inpatient detoxification nor specialized OAT compared to low-threshold municipality care were associated with changes in substance use over time. Future research needs to evaluate the impact on substance use and healthy survival of multiple health care interventions to this patient group.

Is the tobacco ‘footfall’ argument justified for tobacco purchases in New Zealand convenience stores?

2020 ◽  
pp. tobaccocontrol-2020-056032
Author(s):  
Louise Marsh ◽  
Claire Cameron ◽  
Robin Quigg ◽  
Sarah Wood ◽  
Mei-Ling Blank ◽  
...  
Keyword(s):  
New Zealand ◽  
Random Sample ◽  
Retail Trade ◽  
Future Research ◽  
Trade Associations ◽  
Tobacco Sales ◽  
Convenience Stores ◽  
The Mean ◽  
The Impact

IntroductionNew Zealand’s Smokefree 2025 goal aims to greatly decrease the availability of tobacco. One option is to cease the sale of tobacco from convenience stores. However, tobacco companies and retail trade associations oppose this move and have argued that customers who purchase tobacco drive footfall and spend more than non-tobacco customers. The aim of this study is to test the validity of industry claims about the importance of tobacco to convenience stores.MethodsDuring November and December 2019, immediate postpurchase surveys were undertaken with customers on exit from a random sample of 100 convenience stores in two New Zealand cities. We estimated the mean number of items purchased, including tobacco and non-tobacco items, and mean expenditure on non-tobacco items.ResultsOf the 3399 transactions recorded, 13.8% included tobacco, of which 8.3% comprised tobacco only and 5.5% included tobacco and non-tobacco items. The mean number of transactions containing both tobacco and non-tobacco items was 1.98, and 1.87 for those containing non-tobacco items only. Customers who purchased tobacco and non-tobacco items spent on average NZ$6.99 on non-tobacco items, whereas customers who purchased non-tobacco items only, spent on average NZ$5.07.ConclusionsOur results do not support claims that tobacco drives one-quarter of footfall into stores or that customers who purchase tobacco spend almost twice as much as non-tobacco customers. Combined purchases of tobacco and non-tobacco items constituted 5.5% of transactions; the impact on a store’s profitability of removing tobacco sales is unknown and could be the focus of future research.

scholarly journals Droplet Activation and Mixing in Large-Eddy Simulation of a Shallow Cumulus Field

2012 ◽  
Vol 69 (2) ◽  
pp. 444-462 ◽  
Author(s):  
Joanna Slawinska ◽  
Wojciech W. Grabowski ◽  
Hanna Pawlowska ◽  
Hugh Morrison
Keyword(s):  
Cloud Condensation Nuclei ◽  
Cloud Base ◽  
Subgrid Scale ◽  
Cloud Droplets ◽  
Microphysics Scheme ◽  
Free Air ◽  
Aircraft Observations ◽  
The Mean ◽  
Cloud Activation ◽  
The Impact

Abstract This paper presents the application of a double-moment bulk warm-rain microphysics scheme to the simulation of a field of shallow convective clouds based on Barbados Oceanographic and Meteorological Experiment (BOMEX) observations. The scheme predicts the supersaturation field and allows secondary in-cloud activation of cloud droplets above the cloud base. Pristine and polluted cloud condensation nuclei (CCN) environments, as well as opposing subgrid-scale mixing scenarios, are contrasted. Numerical simulations show that about 40% of cloud droplets originate from CCN activated above the cloud base. Significant in-cloud activation leads to the mean cloud droplet concentration that is approximately constant with height, in agreement with aircraft observations. The in-cloud activation affects the spatial distribution of the effective radius and the mean albedo of the cloud field. Differences between pristine and polluted conditions are consistent with the authors’ previous study, but the impact of the subgrid-scale mixing is significantly reduced. Possible explanations of the latter involve physical and numerical aspects. The physical aspects include (i) the counteracting impacts of the subgrid-scale mixing and in-cloud activation and (ii) the mean characteristics of the environmental cloud-free air entrained into a cloud. A simple analysis suggests that the entrained cloud-free air is on average close to saturation, which leads to a small difference between various mixing scenarios. The numerical aspect concerns the relatively small role of the parameterized subgrid-scale mixing when compared to mixing and evaporation due to numerical diffusion. Although the results are consistent with aircraft observations, limitations of the numerical model due to low spatial resolution call for higher-resolution simulations where entrainment processes are resolved rather than mostly parameterized as in the current study.

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