Analysis of a seeder‐feeder and freezing drizzle event

Abstract

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.

Mountain Waves Analysis in the Vicinity of the Madrid-Barajas Airport Using the WRF Model

“…(i) Goddard (GOD) [43]: this scheme is optimized to simulate condensation and evaporation processes; it has been proven to be a good performer in aircraft icing studies in the Iberian Peninsula, although not specifically for mountain waves [38,44]. (ii) ompson (THO) [45]: this microphysics scheme is defined to improve the forecast of aircraft icing, since it considers mixed-phase processes relative to another bulk microphysics.…”

Numerical simulations of snowfall events: Sensitivity analysis of physical parameterizations

“…Finally, we used the Eta surface layer scheme described by Janjic [1996]. These schemes have been used by Gascón et al [2015] and Fernández-González et al [2015] for the mainland Iberian Peninsula, with satisfactory results.…”

Natural Seeder‐Feeder Process Originating From Mixed‐Phase Clouds Observed With Polarization Lidar and Radiosonde at a Mid‐Latitude Plain Site

“…Exceptionally, at relatively warmer temperatures, quite a few ice-containing clouds are related to other processes including secondary ice production (e.g., the Hallett-Mossop process (Hallett & Mossop, 1974), ice particle fragmentation upon ice-ice collisions (Vardiman, 1978), and the release of small ice particles upon the freezing of drizzle-sized droplets (Lauber et al, 2018)) and seeder-feeder mechanisms (Dong et al, 2020(Dong et al, , 2021Roe, 2005).The seeder-feeder mechanism is a phenomenon in which ice crystals from an upper cloud, as "seeds," fall into a lower-lying liquid cloud and then grow larger within the liquid cloud by riming or vapor deposition via the Wegener-Bergeron-Findeisen process. The lower-lying liquid cloud serves as a "feeder" since it supplies moisture to induce the growth of incoming ice crystals (Fernández-González et al, 2015;Rutledge & Hobbs, 1983). This process is to some extent like natural aerosols serving as ice-nucleating particles to trigger heterogeneous ice formation in mixed-phase clouds (Chen et al, 2016(Chen et al, , 2021Yang et al, 2021).…”