Theoretical analysis of mixing in liquid clouds – Part 3: Inhomogeneous
mixing

Pinsky, Mark; Хаин, А.; Korolev, Alexei

doi:10.5194/acp-16-9273-2016

Cited by 45 publications

(26 citation statements)

References 35 publications

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“…Isobaric mixing of two nearly saturated volumes with T 1 = T 2 may result in supersaturated environment (e.g., Rogers, 1976;Bohren and Albrecht, 1998). Mixing resulting in supersaturation is different in principle from the mixing with evaporating droplets.…”

Section: Effect Of Temperature Case T 1 = Tmentioning

confidence: 99%

“…The evaporation time required to reach equilibrium during homogeneous mixing is discussed in detail in Pinsky et al (2016b), and it is usually limited by a few tens of seconds. However, progressive mixing is not limited in time.…”

Section: Expected Relationships Between the Momentsmentioning

confidence: 99%

“…These two types of mixing present two extreme regimes of mixing. The following two papers provide a detailed analysis of the time-dependent processes during homogeneous (Pinsky et al, 2016a) and inhomogeneous (Pinsky et al, 2016b) mixing where non-extreme regimes are considered as well.…”

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Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

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Abstract. The present study considers final stages of incloud mixing in the framework of classical concept of homogeneous and extreme inhomogeneous mixing. Simple analytical relationships between basic microphysical parameters were obtained for homogeneous and extreme inhomogeneous mixing based on the adiabatic consideration. It was demonstrated that during homogeneous mixing the functional relationships between the moments of the droplets size distribution hold only during the primary stage of mixing. Subsequent random mixing between already mixed parcels and undiluted cloud parcels breaks these relationships. However, during extreme inhomogeneous mixing the functional relationships between the microphysical parameters hold both for primary and subsequent mixing. The obtained relationships can be used to identify the type of mixing from in situ observations. The effectiveness of the developed method was demonstrated using in situ data collected in convective clouds. It was found that for the specific set of in situ measurements the interaction between cloudy and entrained environments was dominated by extreme inhomogeneous mixing.

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Section: Effect Of Temperature Case T 1 = Tmentioning

confidence: 99%

Section: Expected Relationships Between the Momentsmentioning

confidence: 99%

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Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

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“…The second timescale characterizes rate of droplet evaporation and corresponding changes of supersaturation. In this study, as well as later in study by Pinsky et al (2016) (hereafter, Part 3), it will be shown that the characteristic evaporation time is the phase relaxation time τ pr , which determines the rate of change of supersaturation during condensation or evaporation (Mazin, 1968;Korolev and Mazin, 2003) …”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing

et al. 2016

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Abstract. Evolution of monodisperse and polydisperse droplet size distributions (DSD) during homogeneous mixing is analyzed. Time-dependent universal analytical expressions for supersaturation and liquid water content are derived. For an initial monodisperse DSD, these quantities are shown to depend on a sole non-dimensional parameter. The evolution of moments and moment-related functions in the course of homogeneous evaporation of polydisperse DSD is analyzed using a parcel model.It is shown that the classic conceptual scheme, according to which homogeneous mixing leads to a decrease in droplet mass at constant droplet concentration, is valid only in cases of monodisperse or initially very narrow polydisperse DSD. In cases of wide polydisperse DSD, mixing and successive evaporation lead to a decrease of both mass and concentration, so the characteristic droplet sizes remain nearly constant. As this feature is typically associated with inhomogeneous mixing, we conclude that in cases of an initially wide DSD at cloud top, homogeneous mixing is nearly indistinguishable from inhomogeneous mixing.

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“…However, C r and the directly related relative dispersion 20 are important for models as the relative dispersion defines the effective rate of mixing of a puff and therefore the decay rate of concentration fluctuations (e.g. Sawford, 2004;Cassiani et al, 2005;Pinsky et al, 2016;Marro et al, 2018).…”

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Characterising vertical turbulent dispersion by observing artificially released SO<sub>2</sub> puffs with UV cameras

Dinger

Stebel

Cassiani

et al. 2018

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Abstract. In atmospheric tracer experiments, a substance is released into the turbulent atmospheric flow to study the dispersion parameters of the atmosphere. That can be done by observing the substance's concentration distribution downwind of the source. Past experiments have suffered from the fact that observations were only made at few discrete locations and/or at low time resolution. The COMTESSA project (Camera Observation and Modelling of 4D Tracer Dispersion in the Atmosphere) is the first attempt at using ultraviolet (UV) camera observations to sample the three-dimensional (3D) concentration distribution 5 in the atmospheric boundary layer at high spatial and temporal resolution. For this, during a three-week campaign in Norway in July 2017, sulfur dioxide (SO 2 ), a nearly passive tracer, was artificially released in continuous plumes and nearly-instantaneous puffs from a 9 m high tower. Column-integrated SO 2 concentrations were observed with six UV SO 2 cameras with sampling rates of several Hertz and a spatial resolution of a few centimetres. The atmospheric flow was characterised by eddy covariance measurements of heat and momentum fluxes at the release mast and two additional towers. By measuring simultaneously with 10 six UV cameras positioned in a half circle around the release point, we could collect a data set of spatially and temporally resolved tracer column densities from six different directions, allowing a tomographic reconstruction of the 3D concentration field. However, due to unfavourable cloudy conditions on all measurement days and their restrictive effect on the SO 2 camera technique, the presented data set is limited to case studies. In this paper, we present a feasibility study demonstrating that the turbulent dispersion parameters can be retrieved from images of artificially released puffs. The 3D trajectories of the centre of 15 mass of the puffs were reconstructed enabling both a direct determination of the centre of mass meandering and a scaling of the image pixel dimension to the position of the puff. The latter made it possible to retrieve the temporal evolution of the puff spread projected to the image plane. The puff spread is a direct measure of the relative dispersion process. Combining meandering and relative dispersion, the absolute dispersion could be retrieved. The turbulent dispersion in the vertical is then used to estimate the effective source size, source time scale and the Lagrangian integral time. In principle, the Richardson-Obukhov constant 20 of relative dispersion in the inertial subrange could be also obtained, but the observation time was not sufficiently long in comparison to the source time scale to allow an observation of this dispersion range. While the feasibility of the methodology 1 Atmos. Meas. Tech. Discuss., https://doi

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Theoretical analysis of mixing in liquid clouds – Part 3: Inhomogeneous mixing

Cited by 45 publications

References 35 publications

Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing

Characterising vertical turbulent dispersion by observing artificially released SO<sub>2</sub> puffs with UV cameras

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Theoretical analysis of mixing in liquid clouds – Part 3: Inhomogeneous mixing

Cited by 45 publications

References 35 publications

Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing

Characterising vertical turbulent dispersion by observing artificially released SO&lt;sub&gt;2&lt;/sub&gt; puffs with UV cameras

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Product

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Characterising vertical turbulent dispersion by observing artificially released SO<sub>2</sub> puffs with UV cameras