A parameterisation for the activation of cloud drops including the effects of semi-volatile organics

Abstract. We present a parameterisation of aerosol activation, including co-condensation of semi-volatile organics, for warm clouds that has applications in large-scale numerical models. The scheme is based on previously developed parameterisations that are in the literature, but has two main modifications. The first is that the total aerosol mass is modified by the condensation of organic vapours entering cloud-base, whereas the second is that this addition of mass acts to modify the median diameter and the geometric standard deviation of the aerosol size distribution. It is found that the scheme is consistent with parcel model calculations of co-condensation under different regimes. Such a parameterisation may find use in evaluating important feedbacks in climate models.

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A parameterisation for the activation of cloud drops including the effects of semi-volatile organics

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-2289-2014 ◽

2014 ◽

Vol 14 (5) ◽

pp. 2289-2302 ◽

Cited By ~ 5

Author(s):

P. J. Connolly ◽

D. O. Topping ◽

F. Malavelle ◽

G. McFiggans

Keyword(s):

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Aerosol Size Distribution ◽

Geometric Standard Deviation ◽

Cloud Base ◽

Volatile Organics ◽

Model Calculations ◽

Aerosol Mass ◽

Median Diameter

Abstract. We present a parameterisation of aerosol activation, including co-condensation of semi-volatile organics, for warm clouds that has applications in large-scale numerical models. The scheme is based on previously developed parameterisations that are in the literature, but has two main modifications. The first is that the total aerosol mass is modified by the condensation of organic vapours entering cloud base, whereas the second is that this addition of mass acts to modify the median diameter and the geometric standard deviation of the aerosol size distribution. It is found that the scheme is consistent with parcel model calculations of co-condensation under different regimes. Such a parameterisation may find use in evaluating important feedbacks in climate models.

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A Theory of the Wind-Driven Beaufort Gyre Variability

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0091.1 ◽

2016 ◽

Vol 46 (11) ◽

pp. 3263-3278 ◽

Cited By ~ 29

Author(s):

Georgy E. Manucharyan ◽

Michael A. Spall ◽

Andrew F. Thompson

Keyword(s):

Time Scales ◽

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Mesoscale Eddy ◽

Eddy Diffusivity ◽

The Arctic ◽

Equilibration Time ◽

Ekman Pumping ◽

Beaufort Gyre

AbstractThe halocline of the Beaufort Gyre varies significantly on interannual to decadal time scales, affecting the freshwater content (FWC) of the Arctic Ocean. This study explores the role of eddies in the Ekman-driven gyre variability. Following the transformed Eulerian-mean paradigm, the authors develop a theory that links the FWC variability to the stability of the large-scale gyre, defined as the inverse of its equilibration time. The theory, verified with eddy-resolving numerical simulations, demonstrates that the gyre stability is explicitly controlled by the mesoscale eddy diffusivity. An accurate representation of the halocline dynamics requires the eddy diffusivity of 300 ± 200 m2 s−1, which is lower than what is used in most low-resolution climate models. In particular, on interannual and longer time scales the eddy fluxes and the Ekman pumping provide equally important contributions to the FWC variability. However, only large-scale Ekman pumping patterns can significantly alter the FWC, with spatially localized perturbations being an order of magnitude less efficient. Lastly, the authors introduce a novel FWC tendency diagnostic—the Gyre Index—that can be conveniently calculated using observations located only along the gyre boundaries. Its strong predictive capabilities, assessed in the eddy-resolving model forced by stochastic winds, suggest that the Gyre Index would be of use in interpreting FWC evolution in observations as well as in numerical models.

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Potential vorticity dynamics of life cycles of blocked weather regimes in the Euro-Atlantic region: A diagnostic framework

10.5194/egusphere-egu21-12847 ◽

2021 ◽

Author(s):

Seraphine Hauser ◽

Christian M. Grams ◽

Michael Riemer ◽

Peter Knippertz ◽

Franziska Teubler

Keyword(s):

Potential Vorticity ◽

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Weather Prediction ◽

Life Cycles ◽

Forecast Errors ◽

Atlantic Region ◽

Weather Regimes ◽

Medium Range

Quasi-stationary, persistent, and recurrent states of the large-scale extratropical circulation, so-called weather regimes, characterize the atmospheric variability on sub-seasonal timescales of several days to a few weeks. Weather regimes featuring a blocking anticyclone are of particular interest due to their long lifetime and potential for high-impact weather. However, state-of-the-art numerical weather prediction and climate models struggle to correctly represent blocking life cycles, which results in large forecast errors at the medium-range to sub-seasonal timescale. Despite progress in recent years, we are still lacking a process-based conceptual understanding of blocked regime dynamics, which hinders a better representation of blocks in numerical models. In particular the relative contributions of dry and moist processes in the onset and maintenance of a block remain unclear.Here we aim to revisit the dynamics of blocking in the Euro-Atlantic region. To this end we investigate the life cycles of blocked weather regimes from a potential vorticity (PV) perspective in ERA5 reanalysis data (from 1979 to present) from the European Centre for Medium-Range Weather Forecasts. We develop a diagnostic PV framework that allows the tracking of negative PV anomalies associated with blocked weather regimes. Complemented by piecewise PV-tendencies - separated into advective and diabatic PV tendencies - we are able to disentangle different physical processes affecting the amplitude evolution of negative PV anomalies associated with blocked regimes. Most importantly, this approach newly enables us to distinguish between the roles of dry and moist dynamics in the initiation and maintenance of blocked weather regimes in a common framework. A first application demonstrates the functionality of the developed PV framework and corroborates the importance of moist-diabatic processes in the initiation and maintenance of a block in a regime life cycle.&#160;

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Modeled Respiratory Tract Deposition of Aerosolized Oil Diluents Used in Δ9-THC-Based Electronic Cigarette Liquid Products

Frontiers in Public Health ◽

10.3389/fpubh.2021.744166 ◽

2021 ◽

Vol 9 ◽

Author(s):

Anand Ranpara ◽

Aleksandr B. Stefaniak ◽

Kenneth Williams ◽

Elizabeth Fernandez ◽

Ryan F. LeBouf

Keyword(s):

Vitamin E ◽

Respiratory Tract ◽

Coconut Oil ◽

Electronic Cigarette ◽

Aerosol Size Distribution ◽

Geometric Standard Deviation ◽

Aerosol Mass ◽

Respiratory Deposition ◽

Liquid Products ◽

Particle Dosimetry

Electronic cigarette, or vaping, products (EVP) heat liquids (“e-liquids”) that contain substances (licit or illicit) and deliver aerosolized particles into the lungs. Commercially available oils such as Vitamin-E-acetate (VEA), Vitamin E oil, coconut, and medium chain triglycerides (MCT) were often the constituents of e-liquids associated with an e-cigarette, or vaping, product use-associated lung injury (EVALI). The objective of this study was to evaluate the mass-based physical characteristics of the aerosolized e-liquids prepared using these oil diluents. These characteristics were particle size distributions for modeling regional respiratory deposition and puff-based total aerosol mass for estimating the number of particles delivered to the respiratory tract. Four types of e-liquids were prepared by adding terpenes to oil diluents individually: VEA, Vitamin E oil, coconut oil, and MCT. A smoking machine was used to aerosolize each e-liquid at a predetermined puff topography (volume of 55 ml for 3 s with 30-s intervals between puffs). A cascade impactor was used to collect the size-segregated aerosol for calculating the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD). The respiratory deposition of EVP aerosols on inhalation was estimated using the Multiple-Path Particle Dosimetry model. From these results, the exhaled fraction of EVP aerosols was calculated as a surrogate of secondhand exposure potential. The MMAD of VEA (0.61 μm) was statistically different compared to MCT (0.38 μm) and coconut oil (0.47 μm) but not to Vitamin E oil (0.58 μm); p < 0.05. Wider aerosol size distribution was observed for VEA (GSD 2.35) and MCT (GSD 2.08) compared with coconut oil (GSD 1.53) and Vitamin E oil (GSD 1.55). Irrespective of the statistical differences between MMADs, dosimetry modeling resulted in the similar regional and lobular deposition of particles for all e-liquids in the respiratory tract. The highest (~0.08 or more) fractional deposition was predicted in the pulmonary region, which is consistent as the site of injury among EVALI cases. Secondhand exposure calculations indicated that a substantial amount of EVP aerosols could be exhaled, which has potential implications for bystanders. The number of EVALI cases has declined with the removal of VEA; however, further research is required to investigate the commonly available commercial ingredients used in e-liquid preparations.

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Roughness, age and drift trajectories of sea ice in large-scale simulations and their use in model verifications

Annals of Glaciology ◽

10.3189/s0260305500014105 ◽

1997 ◽

Vol 25 ◽

pp. 237-240 ◽

Cited By ~ 10

Author(s):

Markus Harder

Keyword(s):

Sea Ice ◽

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Salt Water ◽

Ice Cover ◽

Ice Thickness ◽

Polar Regions ◽

Prognostic Variables ◽

New Variables

In polar regions, the exchange of heat, fresh water and salt water, and momentum between ocean and atmosphere is strongly affected by the presence of sea-ice cover. As a growing number of climate models include a dynamic–thermodynamic sea-ice component to take these effects into account, it might be asked whether sea ice is adequately represented in these simulations, and how far these simulations fit with physical observations.Sea ice in the classical models (Hibler, 1979; Parkinson and Washington, 1979) that have been available for two decades, is regarded as a two-dimensional (2-D) continuum covering the ocean surface. The prognostic variables describing the ice pack are horizontal ice velocity, areal coverage (ice concentration), and ice thickness. In numerical models, these variables and their evolution in space and time are solved on an Eulerian grid.A number of observational data are available to verify the model results. Sea-ice drift is observed from drifting buoys deployed on ice floes. Areal sea-ice coverage can be observed with satellite-borne passive-microwave sensors (SMMR, SSM/I). For ice thickness, which cannot be observed with remote-sensing techniques, rather few, scattered observations from upward-looking sonars on submarines and moorings are available.This article gives an overview of three additional variables representing sea ice in large-scale climate models. These are (1) roughness, (2) age of the ice, introduced as two prognostic variables, and (3) simulated trajectories of ice motion, which are diagnosed from the Eulerian velocity grid. The new variables enable a more detailed look at sea ice in models, helping to understand better the coupled dynamic–thermodynamic processes determining the polar ice cover. Further, the new variables offer important, additional possibilities for comparing the simulated sea-ice properties with available observations.

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Ship-based aerosol measurements in the Southern Ocean

10.5194/egusphere-egu21-12327 ◽

2021 ◽

Author(s):

Floortje van den Heuvel ◽

Thomas Lachlan-Cope ◽

Jonathan Witherstone ◽

Dean Hurren ◽

Anna Jones

Keyword(s):

Southern Ocean ◽

Large Scale ◽

Climate Models ◽

Climate Model ◽

Numerical Models ◽

Cloud Microphysics ◽

Wave Radiation ◽

Atlantic Sector ◽

Radiation Fluxes ◽

Travel Restrictions

Our limited understanding of clouds is a major source of uncertainty in climate sensitivity and climate model projections. The Southern Ocean is the largest region on Earth where climate models present large biases in short and long wave radiation fluxes which in turn affect the representation of sea surface temperatures, sea ice and ultimately large scale circulation in the Southern Hemisphere. Evidence suggests that the poor representation of mixed phase clouds at the micro- and macro scales is responsible for the model biases in this region. The Southern Ocean Clouds (SOC) project will be a multi-scale, multi-platform approach with the aim of improving understanding of aerosol and cloud microphysics in this region, and their representation in numerical models. Although this years&#8217; first SOC measurement season has suffered greatly from travel restrictions, we have installed an Optical Particle Counter (OPC) on a ship (The James Clark Ross &#8211; JCR) and recorded aerosol measurements as it was travelling through the Atlantic sector of the Southern Ocean towards the Antarctic Peninsula, and while the ship was moored at South Georgia and Port Stanley. Over the course of one month, the OPC recorded particle sizes between 0.35 and 40 micrometers every six seconds. This study will present the data from this first, rather short Antarctic SOC season. It will present the analyses of the obtained OPC data alongside satellite observations and model reanalyses in the same region.

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Re-examining inferences from Hadley cell theory on tropical expansion under global warming throughout the seasonal cycle

10.5194/egusphere-egu2020-11539 ◽

2020 ◽

Author(s):

Spencer Hill ◽

Jonathan Mitchell ◽

Simona Bordoni

Keyword(s):

Global Warming ◽

Temperature Gradient ◽

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Global Climate Models ◽

Hadley Cell ◽

Critical Examination ◽

Cell Width ◽

Hadley Cells

Simulations of global warming in numerical models ranging from full-complexity atmosphere-ocean global climate models (GCMs) to highly idealized, dry, atmospheric GCMs almost invariably feature poleward expansion of the annual-mean Hadley cell extent.&#160; The attendant widening of the subtropical dry zones underlying the Hadley cell descending branches makes understanding this response of the large-scale circulation to climate change of paramount societal and ecological importance.&#160; Two theories, one that neglects the role of large-scale eddy process and one that does not, yield similar but ultimately distinct dependencies of the Hadley cell width on planetary parameters, including those such as the equator-to-pole temperature gradient that also robustly change under global warming.&#160; A common approach, therefore, is to use the responses of these parameters diagnosed from GCM simulations to make arguments about their influence on the Hadley cell widening.&#160; This talk offers a critical examination of that approach.The approach's key flaw is that the quantities such as the equator-to-pole temperature gradient that appear in the theoretical scalings refer to their values in the *absence* of any large-scale overturning circulation, Hadley cells or eddies, i.e. in the hypothetical state of latitude-by-latitude radiative convective equilibrium (RCE).&#160; This RCE state is what "forces" the Hadley cells, and once the Hadley cells emerge they modify (among others) the equator-to-pole temperature gradient.&#160; Using these theories to understand the Hadley cell response to increased CO2 therefore requires analyzing the responses of the hypothetical RCE state to the increased CO2, which we do via single column model simulations.&#160; In addition, we present a new scaling for the Hadley cell extent applicable to the solsticial seasons that, unlike the existing scalings, does not depend sensitively on the presence or absence of large-scale eddies, which we use in conjunction with solsticial RCE simulations to clarify arguments regarding tropical expansion over the course of the annual cycle in addition to the annual mean.&#160; The implications for these refined theoretical arguments on results from prior studies and on constraining future Hadley cell expansion are discussed.

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Roughness, Age and Drift Trajectories of Sea Ice in Large-Scale Simulations and their Use in Model Verifications

Annals of Glaciology ◽

10.1017/s0260305500014105 ◽

1997 ◽

Vol 25 ◽

pp. 237-240 ◽

Cited By ~ 6

Author(s):

Markus Harder

Keyword(s):

Sea Ice ◽

Large Scale ◽

Climate Models ◽

Numerical Models ◽

Salt Water ◽

Ice Cover ◽

Ice Thickness ◽

Polar Regions ◽

Prognostic Variables ◽

New Variables

In polar regions, the exchange of heat, fresh water and salt water, and momentum between ocean and atmosphere is strongly affected by the presence of sea-ice cover. As a growing number of climate models include a dynamic-thermodynamic sea-ice component to take these effects into account, it might be asked whether sea ice is adequately represented in these simulations, and how far these simulations fit with physical observations.Sea ice in the classical models (Hibler, 1979; Parkinson and Washington, 1979) that have been available for two decades, is regarded as a two-dimensional (2-D) continuum covering the ocean surface. The prognostic variables describing the ice pack are horizontal ice velocity, areal coverage (ice concentration), and ice thickness. In numerical models, these variables and their evolution in space and time are solved on an Enlerian grid.A number of observational data are available to verify the model results. Sea-ice drift is observed from drifting buoys deployed on ice floes. Areal sea-ice coverage can be observed with satellite-borne passive-microwave sensors (SMMR, SSM/I). For ice thickness, which cannot be observed with remote-sensing techniques, rather few, scattered observations from upward-looking sonars on submarines and moorings are available.This article gives an overview of three additional variables representing sea ice in large-scale climate models. These are (1) roughness, (2) age of the ice. introduced as two prognostic variables, and (3) simulated trajectories of ice motion, which are diagnosed from the Enlerian velocity grid. The new variables enable a more detailed look at sea ice in models, helping to understand better the coupled dynami-thermodynamic processes determining the polar ice cover. Further, the new variables offer important, additional possibilities for comparing the simulated sea-ice properties with available observations.

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Airway deposition of hygroscopic heterodispersed aerosols: results of a computer calculation

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.3.1195 ◽

1987 ◽

Vol 63 (3) ◽

pp. 1195-1204 ◽

Cited By ~ 39

Author(s):

D. D. Persons ◽

G. D. Hess ◽

W. J. Muller ◽

P. W. Scherer

Keyword(s):

Computer Calculation ◽

Particle Diameter ◽

Theoretical Data ◽

Bronchial Tree ◽

Geometric Standard Deviation ◽

Breath Holding ◽

Aerosol Mass ◽

Median Diameter ◽

Airway Deposition ◽

Mass Median

A new computer model is developed and used to calculate the deposition of inhaled heterodispersed hygroscopic aerosols for mouth breathing in a Weibel symmetric bronchial tree. The model was first validated by obtaining good agreement with recent experimental and theoretical data on regional and total airway deposition of monodispersed and heterodispersed nonhygroscopic aerosols. The model was then used to obtain predictions of regional and total deposition of heterodispersed hygroscopic aerosol particles (droplets of NaCl solutions). Parameters that were varied in the hygroscopic calculations include initial droplet NaCl concentration, time of inspiration and expiration, volume of aerosol inspired, period of breath holding, and initial inhaled lognormal aerosol mass median diameter and geometric standard deviation. Results of the computer calculations show that increasing heterodispersity tends to flatten and broaden regional deposition curves when fraction of inhaled mass deposited is plotted vs. inhaled mass median aerodynamic particle diameter. Hygroscopicity is shown to increase tracheobronchial and pulmonary airway deposition with hypertonic NaCl solution aerosols showing increases over isotonic and nonhygroscopic aerosols of up to 200%.

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Aerosol optical properties in the southeastern United States in summer – Part 2: Sensitivity of aerosol optical depth to relative humidity and aerosol parameters

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-31471-2015 ◽

2015 ◽

Vol 15 (21) ◽

pp. 31471-31499 ◽

Cited By ~ 6

Author(s):

C. A. Brock ◽

N. L. Wagner ◽

B. E. Anderson ◽

A. Beyersdorf ◽

P. Campuzano-Jost ◽

...

Keyword(s):

Refractive Index ◽

Relative Humidity ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Climate Models ◽

Mixed Boundary ◽

Geometric Standard Deviation ◽

Aerosol Mass ◽

Southeastern Us ◽

Aerosol Parameters

Abstract. Aircraft observations of meteorological, trace gas, and aerosol properties were made between May and September 2013. Regionally representative aggregate vertical profiles of median and interdecile ranges of the measured parameters were constructed from 37 individual aircraft profiles made in the afternoon when a well-mixed boundary layer with typical fair-weather cumulus was present (Wagner et al., 2015). We use these 0–4 km aggregate profiles and a simple model to calculate the sensitivity of aerosol optical depth (AOD) to changes in dry aerosol mass, relative humidity, mixed layer height, the central diameter and width of the particle size distribution, hygroscopicity, and dry and wet refractive index, while holding the other parameters constant. The calculated sensitivity is a result of both the intrinsic sensitivity and the observed range of variation of these parameters. These observationally based sensitivity studies indicate that the relationship between AOD and dry aerosol mass in these conditions in the southeastern US can be highly variable and is especially sensitive to relative humidity (RH). For example, calculated AOD ranged from 0.137 to 0.305 as the RH was varied between the 10th and 90th percentile profiles with dry aerosol mass held constant. Calculated AOD was somewhat less sensitive to aerosol hygroscopicity, mean size, and geometric standard deviation, σg. However, some chemistry-climate models prescribe values of σg substantially larger than we or others observe, leading to potential high biases in model-calculated AOD of ~ 25 %. Finally, AOD was least sensitive to observed variations in dry and wet aerosol refractive index and to changes in the height of the well-mixed surface layer. We expect these findings to be applicable to other moderately polluted and background continental airmasses in which an accumulation mode between 0.1–0.5 μm diameter dominates aerosol extinction.

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