Detection of Potential Refreezing Rain Area Using Dual-Polarization Variables and Wet-Bulb Temperature

Various types of surface precipitation occur depending on the vertical temperature structure of atmosphere. Generally, snow falls when the surface temperature is below zero degree, while rain falls when it is above freezing level. Refreezing rain occurs when snow particles pass through a warm and thick layer of air in the upper atmosphere and then freeze upon contact with the subfreezing surface. The refreezing rain causes major traffic accidents when rain drops freeze on the shaded cold surface on the paved road, high way, or bridge. Since it causes hazardous accidents, it is very important to accurately detect the areas of potential refreezing rain. In order to provide the information about the risk of danger on the road due to refreezing rain, we developed the algorithm to detect the potential refreezing rain area by using dual polarization radar and 3-dimensional temperature structure. We calculated 3-dimensional wet-bulb temperatures using moisture and temperature profiles to check inversion layers, and then the type of hydrometeor from dual-polarization radar was used to investigate the possibility of melting of ice particles within the inversion layer. When snow particles were melted in the inversion layer, the potential refreezing rain area was designated as danger/caution area according to ground temperature conditions. The performance of the algorithm for the potential refreezing rain area was evaluated for the events of refreezing rain (aka. black-ice) during the cold season. We analyzed the hourly and monthly frequencies of detection of the danger/caution area for the cases of traffic accidents caused by refreezing rain.

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Keywords: refreezing rain, dual-polarization radar, wet-bulb temperature, inversion layer, hydrometeors

This research was supported by the "Development of radar based severe weather monitoring technology(KMA2021-03121)" of "Development of integrated application technology for Korea weather radar" project funded by Weather Radar Center, Korea Meteorological Administration.