Observation of a freezing drizzle episode: A case study

Fernández‐González, Sergio; Valero, Francisco; Sanchez, J.L.; Gascón, Estíbaliz; López, Laura Marcela Vásquez; García‐Ortega, Eduardo; Merino, Andrés

doi:10.1016/j.atmosres.2014.06.014

Cited by 18 publications

(9 citation statements)

References 48 publications

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“…At 12:00 UTC, the cold air mass arrived from northeast of D04, causing moderate precipitation. In the prefrontal area, weak precipitation was produced upwind of the Guadarrama Mountains, which may be connected with freezing precipitation in the same icing event described by Fernández‐González et al []. As in the present event, Zhou et al [] observed intensities around 0.5 mm h −1 during a freezing drizzle episode.…”

Section: Mesoscalesupporting

confidence: 75%

“…This event was between two periods of snow recorded at the surface. Observation of this episode using TEcoAgua instrumentation has been described in detail in Fernández‐González et al []. This observation demonstrated that surface icing was originated by the warm rain process; therefore, in this paper we will only consider surface icing caused by this process.…”

Section: Introductionmentioning

confidence: 94%

“…In the afternoon (15:00 UTC), subfreezing temperatures were restricted to high elevations, because the advancing cold air mass dissipated the thermal inversion; this may have also been affected by solar heating. Snow cover at higher altitudes (above 1750 m asl) in the Guadarrama Mountains [ Fernández‐González et al , ] may have helped maintain subfreezing surface temperatures there throughout the day.…”

Section: Mesoscalementioning

confidence: 99%

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Analysis of a seeder‐feeder and freezing drizzle event

et al. 2015

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Surface icing can cause dramatic consequences on human activities. What is more, numerical weather prediction models are not very accurate in determining freezing drizzle, which creates uncertainty when forecasting this type of weather phenomenon. Therefore, it is essential to improve the forecast accuracy of these models for such phenomena to mitigate risks caused by unforeseen freezing drizzle events. On 5 February 2012, an episode of freezing drizzle took place in the Guadarrama Mountains, at the center of the Iberian Peninsula. This episode was preceded by weak snowfall. After the freezing drizzle, moderate snowfall was recorded in the study area. This event was simulated using the Weather Research and Forecasting model. Through this analysis, we identified the meteorological factors at both synoptic scale and mesoscale that caused this episode. Wind perpendicular to an orographic barrier‐generated updrafts and retention of moisture upwind, which caused orographic clouds to appear on the north side of the Guadarrama Mountains. Atmospheric stability prevented cloud formation at midlevels at the time of the freezing drizzle, which maintained cloud top temperatures warmer than −15°C during the episode. The entrance of moisture and instability at midlevels caused cloud top temperatures substantially colder than −15°C, which coincided with snow in the mountain range. Cloud top temperature and thickness control the efficiency of the glaciation process, thereby determining the type of precipitation at the surface. Freezing drizzle risk and in‐cloud icing algorithms were developed with the aim of predicting similar events in the study area, which could mitigate impacts on human activities.

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Section: Mesoscalesupporting

confidence: 75%

Section: Introductionmentioning

confidence: 94%

Section: Mesoscalementioning

confidence: 99%

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Analysis of a seeder‐feeder and freezing drizzle event

et al. 2015

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“…On the plateau, accumulations rarely exceed 10–20 cm, whereas in mountain areas they can exceed 2 m or even 3 m. There is also great interannual variability of snow accumulation in the mountains of the Iberian peninsula [ López‐Moreno and García‐Ruiz , ]. Freezing rain events are very infrequent in the study area and are virtually restricted to mountainous areas [ Fernández‐González et al , ].…”

Section: Study Areamentioning

confidence: 99%

Numerical simulations of snowfall events: Sensitivity analysis of physical parameterizations

et al. 2015

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Accurate estimation of snowfall episodes several hours or even days in advance is essential to minimize risks to transport and other human activities. Every year, these episodes cause severe traffic problems on the northwestern Iberian Peninsula. In order to analyze the influence of different parameterization schemes, 15 snowfall days were analyzed with the Weather Research and Forecasting (WRF) model, defining three nested domains with resolutions of 27, 9, and 3 km. We implemented four microphysical parameterizations (WRF Single‐Moment 6‐class scheme, Goddard, Thompson, and Morrison) and two planetary boundary layer schemes (Yonsei University and Mellor‐Yamada‐Janjic), yielding eight distinct combinations. To validate model estimates, a network of 97 precipitation gauges was used, together with dichotomous data of snowfall presence/absence from snowplow requests to the emergency service of Spain and observatories of the Spanish Meteorological Agency. The results indicate that the most accurate setting of WRF for the study area was that using the Thompson microphysical parameterization and Mellor‐Yamada‐Janjic scheme, although the Thompson and Yonsei University combination had greater accuracy in determining the temporal distribution of precipitation over 1 day. Combining the eight deterministic members in an ensemble average improved results considerably. Further, the root mean square difference decreased markedly using a multiple linear regression as postprocessing. In addition, our method was able to provide mean ensemble precipitation and maximum expected precipitation,which can be very useful in the management of water resources. Finally, we developed an application that allows determination of the risk of snowfall above a certain threshold.

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“…Of these incidents, the towers at an altitude of over 300 meters accounted for 53.1% of the total collapsed towers [5,6]. High wind speed or warmer, and low concentrations of both ice crystals and ice nuclei, the formation of freezing drizzle would be more favorable [43].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Freezing Drizzle, Sleet and Snow on Microphysical Characteristics of Supercooled Fog during the Icing Process in a Mountainous Area

et al. 2016

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Abstract:Both the similar and different effects of freezing drizzle, sleet and snow on microphysical properties of supercooled fog were analyzed for fourteen events during a comprehensive wire icing, fog, and precipitation observation experiment conducted at Enshi radar station (30 • 17 N, 109 • 16 E; 1722 m a.s.l.) on a hilltop in Shibanling, Hubei, China. Liquid precipitation is in a relatively stable form in mountainous areas. Short-term precipitation (1-3 h) is dominant with temperature below 0 • C. The wet scavenging effect of freezing drizzle on small fog droplets with a size range less than 6-12 µm is weak but is stronger for fog droplets with a larger size, which is opposite to the effects of solid precipitation, broadening the fog droplet spectra significantly. As the fog droplet diameter increases, the distributions of droplet spectra change from leptokurtosis to platykurtosis and from positive skewness to negative skewness. Occurrence of freezing drizzle would improve the positive correlation of N-r in dissipation and oscillation periods, resulting in the N-r relationship having a weak negative correlation in the maturity period, and resulting in the transition of the N-L and N-r relationships into positive correlations in the development period. Meanwhile, the emergence of solid precipitation particles would result in negative values for the correlation coefficients of N-L and N-r. The change in relationships among the microphysical properties was caused by the occurrence of different phase precipitation, showing the influence on the main microphysical mechanisms of supercooled fog.

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Observation of a freezing drizzle episode: A case study

Cited by 18 publications

References 48 publications

Analysis of a seeder‐feeder and freezing drizzle event

Analysis of a seeder‐feeder and freezing drizzle event

Numerical simulations of snowfall events: Sensitivity analysis of physical parameterizations

The Effect of Freezing Drizzle, Sleet and Snow on Microphysical Characteristics of Supercooled Fog during the Icing Process in a Mountainous Area

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