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John V. Cortinas - One of the best experts on this subject based on the ideXlab platform.
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an analysis of Freezing Rain Freezing drizzle and ice pellets across the united states and canada 1976 90
Weather and Forecasting, 2004Co-Authors: John V. Cortinas, Christopher C. Robbins, Ben C. Bernstein, Walter J StrappAbstract:Abstract A comprehensive analysis of Freezing Rain, Freezing drizzle, and ice pellets was conducted using data from surface observations across the United States and Canada. This study complements other studies of Freezing precipitation in the United States and Canada, and provides additional information about the temporal characteristics of the distribution. In particular, it was found that during this period 1) spatial variability in the annual frequency of Freezing precipitation and ice pellets is large across the United States and Canada, and these precipitation types occur most frequently across the central and eastern portions of the United States and Canada, much of Alaska, and the northern shores of Canada; 2) Freezing precipitation and ice pellets occur most often from December to March, except in northern Canada and Alaska where it occurs during the warm season, as well; 3) Freezing Rain and Freezing drizzle appear to be influenced by the diurnal solar cycle; 4) Freezing precipitation is often s...
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An Analysis of Freezing Rain, Freezing Drizzle, and Ice Pellets across the United States and Canada: 1976–90
Weather and Forecasting, 2004Co-Authors: John V. Cortinas, Christopher C. Robbins, Ben C. Bernstein, J. Walter StrappAbstract:Abstract A comprehensive analysis of Freezing Rain, Freezing drizzle, and ice pellets was conducted using data from surface observations across the United States and Canada. This study complements other studies of Freezing precipitation in the United States and Canada, and provides additional information about the temporal characteristics of the distribution. In particular, it was found that during this period 1) spatial variability in the annual frequency of Freezing precipitation and ice pellets is large across the United States and Canada, and these precipitation types occur most frequently across the central and eastern portions of the United States and Canada, much of Alaska, and the northern shores of Canada; 2) Freezing precipitation and ice pellets occur most often from December to March, except in northern Canada and Alaska where it occurs during the warm season, as well; 3) Freezing Rain and Freezing drizzle appear to be influenced by the diurnal solar cycle; 4) Freezing precipitation is often s...
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Local and Synoptic Environments Associated with Freezing Rain in the Contiguous United States
Weather and Forecasting, 2002Co-Authors: Christopher C. Robbins, John V. CortinasAbstract:Abstract Local and synoptic conditions associated with Freezing-Rain events in the continental United States, as well as the temporal and spatial variability of these conditions, have been documented for the period 1976–90. It had been postulated that the characteristics of the thermodynamic stratification observed during Freezing Rain would be similar regardless of geographical location. However, through hypothesis testing, it was found that some interregional variability exists in the magnitude of various sounding parameters that the authors felt characterized the important aspects of the thermodynamic profile of Freezing-Rain environments. This variability seems to be related not only to local effects resulting from terRain variations and nearby water sources, but also from regional differences in synoptic-scale atmospheric environments favorable for Freezing Rain. These results suggest that Freezing-Rain forecast techniques, which rely on critical parameters derived for specific geographical locations...
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A Climatology of Freezing Rain in the Great Lakes Region of North America
Monthly Weather Review, 2000Co-Authors: John V. CortinasAbstract:Abstract A 15-yr climatology of Freezing Rain surrounding the Great Lakes region of North America has been constructed using data from rawinsondes, surface stations, and gridded reanalyses from the National Centers for Environmental Prediction. This climatology reveals that there is a general increase in the Freezing-Rain frequency from west to east; however, the distribution shows large spatial and temporal variability. Most Freezing-Rain events are short lived and occur near sunrise between the months of December and March. Continuous Freezing Rain typically lasts less than 1 h, with 7% of events lasting longer than 5 h. Most Freezing Rain is associated with extratropical cyclones, occurring northeast of the cyclone center in the presence of midlevel upward vertical motion, and air that is nearly saturated at low and midlevels, subFreezing near the surface, and warm (>0°C) at low levels (≈850 hPa). The location of the mean extratropical cyclone track during Freezing-Rain events in the Great Lakes region...
Stanley A. Changnon - One of the best experts on this subject based on the ideXlab platform.
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Freezing Rain events: a major weather hazard in the conterminous US
Natural Hazards, 2006Co-Authors: Tamara G. Houston, Stanley A. ChangnonAbstract:Freezing Rain (FZRA) is well documented as a major weather hazard, producing damage to structures, the environment, and humans, and delaying various operations such as transportation. Assessing the risk of Freezing Rain events requires information for various areas of the nation about the frequency, duration, and intensity of these events along with the associated weather conditions that affect the damage caused by Freezing Rain. This includes temperatures (dry and wet bulb), the amount of precipitation, and winds during Freezing Rain. The purpose of this work was to develop a national and regional climatology of Freezing Rain events in the US for the period of 1928–2001 to addresses these conditions.
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temporal and spatial variations of Freezing Rain in the contiguous united states 1948 2000
Journal of Applied Meteorology, 2003Co-Authors: Stanley A. Changnon, Thomas R. KarlAbstract:Abstract A new Freezing-Rain-days database was used to define the spatial and temporal distributions of Freezing-Rain days across the contiguous United States. The database contained 988 stations, spanning the period 1948–2000. Areas averaging one or more days of Freezing Rain annually included most of the eastern half of the United States and the Pacific Northwest. The national maximum is in portions of New York and Pennsylvania, a result of several weather conditions conducive to Freezing Rain. Other maxima included an east–west zone across the Midwest, an area along the eastern Appalachians, and the Pacific Northwest. The latter two maxima have high frequencies as a result of the mountains, which trap low-level cold air with warm air moving above, resulting in Freezing Rain. National maximum annual values during 1948–2000 were 3–5 times as great as annual averages, but the two patterns were similar. Average patterns for three discrete 17-yr periods between 1948 and 2000 were very similar, but the magni...
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Urban Modification of Freezing-Rain Events
Journal of Applied Meteorology, 2003Co-Authors: Stanley A. ChangnonAbstract:Abstract A new national database for Freezing-Rain occurrences during the 1945–2000 period provided an opportunity for a study of the potential urban effects on Freezing-Rain events. Numerous past studies of snowfall events in urban areas have defined decreases of 10%–35% related to the urban heat island. The heat island, which acts to elevate near-surface temperatures, could also keep some Freezing-Rain situations from occurring in the city. The study involved four cities in the Midwest and Northeast for which the average annual number of days with Freezing Rain are three or more, for which data from in-city stations existed, and for which data for several surrounding rural stations existed. The two largest qualifying cities, New York City, New York, and Chicago, Illinois, had sizable reductions in average and maximum annual Freezing-Rain-day frequencies, ranging from 16% to 43% less than values of surrounding rural stations, and their Freezing-Rain “seasons” were 1–2 months shorter than those in surroun...
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NOTES AND CORRESPONDENCE Urban Modification of Freezing-Rain Events
2003Co-Authors: Stanley A. Changnon, Changnon ClimatologistAbstract:A new national database for Freezing-Rain occurrences during the 1945‐2000 period provided an opportunity for a study of the potential urban effects on Freezing-Rain events. Numerous past studies of snowfall events in urban areas have defined decreases of 10%‐35% related to the urban heat island. The heat island, which acts to elevate near-surface temperatures, could also keep some Freezing-Rain situations from occurring in the city. The study involved four cities in the Midwest and Northeast for which the average annual number of days with Freezing Rain are three or more, for which data from in-city stations existed, and for which data for several surrounding rural stations existed. The two largest qualifying cities, New York City, New York, and Chicago, Illinois, had sizable reductions in average and maximum annual Freezing-Rain-day frequencies, ranging from 16% to 43% less than values of surrounding rural stations, and their Freezing-Rain ‘‘seasons’’ were 1‐2 months shorter than those in surrounding rural areas. The ocean/lake influences at both cities, along with the heat island, also helped to reduce the local incidence of Freezing-Rain events. Two qualifying smaller urban areas, Washington, District of Columbia, and St. Louis, Missouri, had reductions in Freezing-Rain-day occurrences but had no shifts in the length of their Freezing-Rain seasons. Results suggest that Freezing-Rain occurrences in large cities are decreased between 10% and 30% by the heat island, which acts to keep Rain from Freezing to urban surfaces.
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Sources of Data on Freezing Rain and Resulting Damages
Journal of Applied Meteorology, 2003Co-Authors: Stanley A. Changnon, Tamara G. CreechAbstract:Abstract Freezing Rain produces major damages each year in the United States, and various affected groups continue to seek data on the incidence and losses produced by Freezing Rain. The various kinds of data available about Freezing Rain and related damages have been identified and assessed as part of a project to develop long-term databases. Data include long-term records of the occurrences of Freezing Rain, 50-yr records of insured property losses, and measures and estimates of ice loading on wires and structures. Many years of interactions with affected and interested groups and individuals, such as the insurance industry and design engineers, led to the preparation of this summary that describes the various sources of data on Freezing-Rain and ice-storm damages. The benefits and limitations of each form of data are presented to help to guide potential data users.
Shi Yueqin - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of Stratification Structure and Cloud Physics of the Freezing Rain over Southern China in January 2008
Chinese Journal of Atmospheric Sciences, 2012Co-Authors: Shi YueqinAbstract:Southern China suffered four severe Freezing Rain and snow storm processes during January 2008. In this paper, a classical Freezing Rain process during 25-29 January 2008 was selected as a research case. Characteristics of stratification structure and cloud physics of the Freezing Rain were analyzed. Combining with observation, the Freezing Rain process during 28-29 January 2008 was simulated by the CAMS (Chinese Academy of Meteorological Sciences) mesoscale cloud model. The authors studied characteristics of micro-macroscale structure of cloud system over the Freezing Rain area and initially analyzed the microphysical process in the cloud and the mechanism of Freezing Rain formation. The results show that, the stable and thicker melting layer and cold layer at low levels was direct cause that the wide range of Freezing Rain appeared. Two different types of clouds existed over different Freezing Rain areas in this Freezing Rain process. Two types of clouds have different characteristics of stratification structure and cloud physics and mechanism of Freezing Rain formation. Clouds over the Hunan Province Freezing Rain area belonged to mixed-phase cloud: the cloud thickness was deeper, the cloud top temperature was lower, and in the clouds there were large amount of ice-phase particles. Under the consideration of stratification ("cold-warm-cold" layer), the Freezing Rain over Hunan Province was formed by ice-crystal mechanisms (the melting process). That is, the Freezing Rain developed as the falling snow encounters a layer of warm air, and then the snow completely melted and became Rain. As the Rain continued to fall, it passed through a thin layer of cold air just above the surface, cooled to a temperature below Freezing, and formed supercooled drops. When the supercooled Raindrop dropped and struck the ground, or anything else below 0℃, they instantly freeze, forming the Freezing Rain. However, clouds over the Guizhou Province Freezing Rain area belonged to warm clouds: the cloud thickness was thinner, the cloud top temperature was higher, and in the clouds there were little ice-phase particles. Under the consideration of stratification ("warm-cold" layer), the Freezing Rain over Guizhou Province was formed by supercooled warm-Rain processes (collision-coalescence process). Supercooled Raindrops developed by microscopic cloud droplets collecting one another as they fall. Ice processes were not involved in the formation of these Raindrops.
Kathleen F Jones - One of the best experts on this subject based on the ideXlab platform.
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vertical variation of ice loads from Freezing Rain
Cold Regions Science and Technology, 2017Co-Authors: Kathleen F Jones, John B EylanderAbstract:Abstract Ice that accumulates on structures during a Freezing Rain storm can impose significant loads. The design of open structures, including power transmission lines and communication towers, takes into account the vertical load imposed on the structure by the weight of the ice and the horizontal load imposed from the wind drag on the ice-covered structural components. The increase in wind speed with height above ground in the boundary layer increases the horizontal flux of drops of water to the structure, resulting in an increase in ice load with height above ground. This paper evaluates the additional effect of the evaporation of precipitation in the cold air layer at the surface on the vertical variation in the accreted ice load on tall communication towers and masts. The results show that ice thickness increases over the height of the tallest towers, enhancing the thickness increase from the wind speed gradient in the boundary layer. The magnitude of the effect depends on the assumed Rain drop distribution. The evaporation-enhanced ice thickness profiles based on data from Freezing Rain storms at nine weather stations in the United States can be approximated by a power law.
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a simple model for Freezing Rain ice loads
Atmospheric Research, 1998Co-Authors: Kathleen F JonesAbstract:There are many models for hindcasting ice loads from meteorological data measured during Freezing Rain storms. Each model is based on the physics of the ice accretion process and on empirical observations. However, these models predict significantly different ice loads for the same Freezing Rain storm, making it difficult to use model results to determine design ice loads. In this paper, we describe a simple ice load model that can be used to make conservative back-of-the-envelope calculations of ice loads based on the precipitation rate and wind speed. Using historical weather data from Springfield, IL, we compare the ice loads from this model with those from other models and discuss the reasons for the differences between them. We also compare the modeled and measured ice loads from one well-documented storm that occurred at CRREL's Freezing Rain weather station.
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Ice Accretion in Freezing Rain.
1996Co-Authors: Kathleen F JonesAbstract:Abstract : Ice accreted on structures from Freezing Rain causes both increased vertical loads and increased wind loads, due to the larger projected area of the structure. Structural failures initiated by ice loads frequently cause millions of dollars of damage to overhead power and communication lines, towers, and other ice-sensitive structures. There is little information on ice loads to use in the design of these structures, so Freezing-Rain models have been developed for use with weather measurements to determine the severity of accreted ice loads from historical data. This report describes a detailed heat-balance ice accretion model, including the important heat fluxes in Freezing Rain and allowing the accretion of runoff water in the form of icicles. It also presents a simple algorithm for calculating the ice load on components with different diameters and cross sections. Collision efficiency in Freezing Rain and the calculation of the wind-on-ice load are also discussed. Model results are compared with the ice load measured during a recent Freezing Rain storm, and to each other, using 45 years of weather data from Des Moines, Iowa.
Jean Laflamme - One of the best experts on this subject based on the ideXlab platform.
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The climate of Freezing Rain over the province of Québec in Canada: a preliminary analysis
Atmospheric Research, 1998Co-Authors: Jean Laflamme, Gilles PériardAbstract:After 20 yr of data gathering, the Hydro-Quebec network of Passive Ice Meters (PIM) is producing interesting results, namely a map of the Freezing Rain season in the province of Quebec. For other icing parameters, such as the icing frequency and the persistence of ice deposits on structures, differences were found very large and the preliminary analysis was limited to the St.-Lawrence valley. By pooling together maximum values of three stations, it was possible to produce coherent extreme values distributions. While many icing storms are unnoticed at meteorological stations, they seem to be well picked up by the fine grid network of PIM stations, with only 2 observations/day. It is thus possible to precisely map these values and produce better ice load zones for determining limit strengths of structures. The same data are also used to produce risk analyses of other problems related to structures such as flashovers of iced insulators or conductors galloping. Although all Freezing Rain storms are observed by the PIM network, there is a need for more detailed and more frequent observations during major storms. This will help the calibration of PIM measurements and improve our study of icing storms trajectories.
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Spatial variation of extreme values for Freezing Rain
Atmospheric Research, 1995Co-Authors: Jean LaflammeAbstract:Abstract It is still a challenge today to get the statistical approach accepted by some transmission line engineers, namely for Freezing Rain icing loads. They see heavy icing storms as rare events and they still believe that in this case a sound engineering judgment is better than poor statistics. When they are convinced that statistics are good, such as for the flood problem, they do not hesitate to accept the probabilistic approach. Developing extreme values distributions of Freezing-Rain icing is however a difficult task. Because of the relatively small dimension of major Freezing Rain storms, Freezing-Rain icing is not a continuous “variate” at a particular site. One way of improving the statistics is to take simple icing measurements on a fine grid stations network. After only 17 years of measurements with Passive Ice Meters, good fit of extreme values is possible if we use “mesh”extreme values instead of “station” ones. Before pooling extreme values into a “mesh” or “region”distribution, some attention must be given to the homogeneity of the data within a given area. This has been done for four different regions of the province of Quebec with very conclusive results. A mesh of about 50 km seems adequate with a temporal resolution of 12 h. Since transmission lines are spatial constructions, this finding can easily satisfy the need of the design engineers in defining icing loads. And, if some caution is given to identify special topographical features, a better knowledge of the spatial variation of icing makes also possible better line routing.