Microphysical characterization of mixed‐phase clouds

Korolev, Alexei; Isaac, George A.; Cober, Stewart G.; Strapp, J. W.; Hallett, John

doi:10.1256/qj.01.204

Cited by 277 publications

(270 citation statements)

References 54 publications

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“…Cloud periods with values > 0.9 and < 0.1 were classified as glaciated and liquid cloud, respectively, with anything between these values judged to be mixed-phase in nature. The IMF threshold values applied in this work are described in Korolev et al (2003).…”

Section: Discussionmentioning

confidence: 99%

“…Figure 5e shows the frequency of calculated IMF values at JFJ, indicating that mixed-phase clouds dominated the microphysics at JFJ, with significant contributions from liquid (10 and 18 % for 2013 and 2014, respectively) and fully glaciated clouds (29 and 34 % for 2013 and 2014, respectively). Korolev et al (2003) investigated the characteristics of mixed-phase clouds associated with frontal systems from aircraft data collected during several projects that took place in Canada, finding the frequency of liquid and glaciated clouds to be ∼ 26 and ∼ 38 %, respectively, over a similar temperature range. Changes in IMF values were found to occur over different temporal scales (Figs.…”

Section: Cloud Microphysicsmentioning

confidence: 99%

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The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

et al. 2015

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Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L −1 at temperatures around −15 • C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett-Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snowcovered surfaces surrounding the measurement site. Of these we show that hoar frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were < 100 L −1 .

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Section: Discussionmentioning

confidence: 99%

Section: Cloud Microphysicsmentioning

confidence: 99%

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

et al. 2015

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“…7a). To get a rough estimate of the OD of this cloud, we use an ice water content of 0.05 g m −3 , which corresponds to the average ice water content found by Korolev et al (2003) for glaciated frontal clouds at temperatures of around −20 • C. This results in an OD of ≈ 5 in the beginning, growing with the observed thickness of the cloud (Fig. 7e).…”

Section: Radiation-driven Condensation and Evaporation Inmentioning

confidence: 98%

Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

Wærsted¹,

Haeffelin

Dupont

et al. 2017

Atmos. Chem. Phys.

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Abstract. Radiative cooling and heating impact the liquid water balance of fog and therefore play an important role in determining their persistence or dissipation. We demonstrate that a quantitative analysis of the radiation-driven condensation and evaporation is possible in real time using groundbased remote sensing observations (cloud radar, ceilometer, microwave radiometer). Seven continental fog events in midlatitude winter are studied, and the radiative processes are further explored through sensitivity studies. The longwave (LW) radiative cooling of the fog is able to produce 40-70 g m −2 h −1 of liquid water by condensation when the fog liquid water path exceeds 30 g m −2 and there are no clouds above the fog, which corresponds to renewing the fog water in 0.5-2 h. The variability is related to fog temperature and atmospheric humidity, with warmer fog below a drier atmosphere producing more liquid water. The appearance of a cloud layer above the fog strongly reduces the LW cooling relative to a situation with no cloud above; the effect is strongest for a low cloud, when the reduction can reach 100 %. Consequently, the appearance of clouds above will perturb the liquid water balance in the fog and may therefore induce fog dissipation. Shortwave (SW) radiative heating by absorption by fog droplets is smaller than the LW cooling, but it can contribute significantly, inducing 10-15 g m −2 h −1 of evaporation in thick fog at (winter) midday. The absorption of SW radiation by unactivated aerosols inside the fog is likely less than 30 % of the SW absorption by the water droplets, in most cases. However, the aerosols may contribute more significantly if the air mass contains a high concentration of absorbing aerosols. The absorbed radiation at the surface can reach 40-120 W m −2 during the daytime depending on the fog thickness. As in situ measurements indicate that 20-40 % of this energy is transferred to the fog as sensible heat, this surface absorption can contribute significantly to heating and evaporation of the fog, up to 30 g m −2 h −1 for thin fog, even without correcting for the typical underestimation of turbulent heat fluxes by the eddy covariance method. Since the radiative processes depend mainly on the profiles of temperature, humidity and clouds, the results of this paper are not site specific and can be generalised to fog under different dynamic conditions and formation mechanisms, and the methodology should be applicable to warmer and moister climates as well. The retrieval of approximate emissivity of clouds above fog from cloud radar should be further developed.

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“…To avoid artifacts and misinterpretation of data due to possible probe malfunctions, data from the Nevzorov probe were always compared to RICE, King probe, PMS FSSP, OAP-2DC and OAP-2DP data. Calculations of LWC from Nevzorov probe data were made following the procedure described by Korolev et al (2003). Several studies have shown that ice particles may cause a response on the LWC sensor (e.g.…”

Section: Instrumentationmentioning

confidence: 99%

In situ measurements of liquid water content profiles in midlatitude stratiform clouds

Korolev

Isaac

Strapp

et al. 2007

Quart J Royal Meteoro Soc

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Statistical characteristics of 584 liquid water content (LWC) profiles collected mainly in midlatitude supercooled stratiform frontal clouds during five field campaigns are presented. It has been found that the majority (55%) of liquid layers have thickness less than 500 m and the depth of these layers decreases with decreasing temperature. LWC profiles for thin cloud layers are usually close to quasi-adiabatic, whereas for thick clouds they are approximately constant with an average LWC value close to 0.14 g m −3 . Good agreement was observed between cumulative distributions for liquid water paths derived from in situ LWC profiles and those inferred in previous experiments from ground-based 37 GHz radiometers.

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Microphysical characterization of mixed‐phase clouds

Cited by 277 publications

References 54 publications

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

In situ measurements of liquid water content profiles in midlatitude stratiform clouds

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