Phase transformation of mixed‐phase clouds

Korolev, Alexei; Isaac, George A.

doi:10.1256/qj.01.203

Cited by 134 publications

(154 citation statements)

References 36 publications

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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: 81%

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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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Section: Introductionmentioning

confidence: 81%

“…Closed equations describing condensation and/or evaporation in a moving adiabatic air volume were obtained by Pinsky et al (2013). In an unmoving adiabatic volume, evaporation is described by the equation for supersaturation (e.g., Korolev and Mazin, 2003) 1…”

Section: Basic Assumptions and Equationsmentioning

confidence: 99%

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

et al. 2016

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“…For instance, upward air motion and turbulent entrainment of air from above the cloud are critical to maintain liquid water in MPCs. Accurate humidity measurements would also be needed to better identify condensational growth of ice crystals (WBF process or direct condensation of water vapor on ice, as described by Korolev, 2007) and resolve the issue of turbulence and mixing at cloud edges and into clouds. All these parameters, along with radiative flux measurements, are of primary importance to constrain our assumptions on the microphysical processes.…”

Section: Discussion On Statistical Vertical Profilesmentioning

confidence: 99%

Vertical distribution of microphysical properties of Arctic springtime low-level mixed-phase clouds over the Greenland and Norwegian seas

et al. 2017

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Abstract. This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPCs). We compiled and analyzed cloud in situ measurements from four airborne spring campaigns (representing 18 flights and 71 vertical profiles in MPCs) over the Greenland and Norwegian seas mainly in the vicinity of the Svalbard archipelago. Cloud phase discrimination and representative vertical profiles of the number, size, mass and shape of ice crystals and liquid droplets are established. The results show that the liquid phase dominates the upper part of the MPCs. High concentrations (120 cm −3 on average) of small droplets (mean values of 15 µm), with an averaged liquid water content (LWC) of 0.2 g m −3 are measured at cloud top. The ice phase dominates the microphysical properties in the lower part of the cloud and beneath it in the precipitation region (mean values of 100 µm, 3 L −1 and 0.025 g m −3 for diameter, particle concentration and ice water content (IWC), respectively). The analysis of the ice crystal morphology shows that the majority of ice particles are irregularly shaped or rimed particles; the prevailing regular habits found are stellars and plates. We hypothesize that riming and diffusional growth processes, including the WegenerBergeron-Findeisen (WBF) mechanism, are the main growth mechanisms involved in the observed MPCs. The impact of larger-scale meteorological conditions on the vertical profiles of MPC properties was also investigated. Large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations and air mass origins from the south, which can lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling studies are also determined, such as IWC (and LWC) -extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature.

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“…This aerosol indirect effect leads to a longer mixed-phase cloud lifetime, which is opposite the aerosol glaciation indirect effect (Lance et al, 2011). Even more complicated is the coupling of local thermodynamic conditions and large-scale dynamics contributes greatly to the long persistence of mixed-phase clouds (Korolev and Isaac, 2003;Morrison et al, 2012). Bühl et al (2016) estimated ice mass flux at mixed-phase cloud base using ground-based radar measurements and showed that when temperatures are above −15 • C the water depletion due to ice formation is small and the cloud layer is very stable.…”

Section: Introductionmentioning

confidence: 97%

Ice particle production in mid-level stratiform mixed-phase clouds observed with collocated A-Train measurements

et al. 2018

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Abstract. Collocated A-Train CloudSat radar and CALIPSO lidar measurements between 2006 and 2010 are analyzed to study primary ice particle production characteristics in midlevel stratiform mixed-phase clouds on a global scale. For similar clouds in terms of cloud top temperature and liquid water path, Northern Hemisphere latitude bands have layer-maximum radar reflectivity (ZL) that is ∼ 1 to 8 dBZ larger than their counterparts in the Southern Hemisphere. The systematically larger ZL under similar cloud conditions suggests larger ice number concentrations in mid-level stratiform mixed-phase clouds over the Northern Hemisphere, which is possibly related to higher background aerosol loadings. Furthermore, we show that springtime northern midand high latitudes have ZL that is larger by up to 6 dBZ (a factor of 4 higher ice number concentration) than other seasons, which might be related to more dust events that provide effective ice nucleating particles. Our study suggests that aerosol-dependent ice number concentration parameterizations are required in climate models to improve mixedphase cloud simulations, especially over the Northern Hemisphere.

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Phase transformation of mixed‐phase clouds

Cited by 134 publications

References 36 publications

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

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

Vertical distribution of microphysical properties of Arctic springtime low-level mixed-phase clouds over the Greenland and Norwegian seas

Ice particle production in mid-level stratiform mixed-phase clouds observed with collocated A-Train measurements

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