Development of an Ice Event and Icing Impacts Climatology for Georgia

Freezing rain and ice storms (ice events) are known to have a negative impact on society, as they often produce hazardous environmental conditions that affect the power, transportation, aviation, insurance, and public safety industries anywhere from several days to several weeks and months. This is especially true across the southern United States, where ice events are less frequent than in other regions of the country yet in some ways is more vulnerable (dense forests in close proximity to populated areas). While the atmospheric conditions conducive to the formation of ice are well known, few studies have analyzed spatial and temporal changes of ice events and their impacts over an extended period of time.

This study analyzes trends in ice event frequency across Georgia during the cold season (Nov-Mar) for the years 2000-2014 using data from the National Climatic Data Center's Storm Data dataset. Several categories of ice events were created and compared for this analysis: freezing rain (ice accumulation < .25 inches), ice storms (ice accumulation >.25 inches), ice mixed with snow and/or sleet (either < or > .25 inches), cold air damming (CAD) ice events, and synoptic-low ice events without the presence of CAD. Ice event frequency was also compared to several known climate patterns, such as the North Atlantic Oscillation and Arctic Oscillation. For this period of study, ice events were found to be most common in Georgia when snow and/or sleet were also present. It was also found that overall ice event frequency was highest across north Georgia, particularly northeast Georgia and especially when CAD was present. Ice events in which freezing rain was the sole precipitation type were found to be less common. Data provided within Storm Data is subjective and often involves inconsistencies in ice accretion measurements, which was determined to hinder the accuracy of these results, though the extent is unclear. All preliminary conclusions drawn from this study can serve as a basis for future studies aiming to improve short term forecasting and decision support services within the National Weather Service.