Thursday, 1 February 2024: 2:15 PM
Johnson AB (Hilton Baltimore Inner Harbor)
Winter storms produce a variety of hazards, including the potential for multiple precipitation types and transitions between them, which can lead to significant socioeconomic impacts. Precipitation type is dependent on possibly subtle features of the lower-tropospheric temperature profile, which NWP models can struggle to resolve. As such, acquiring accurate atmospheric vertical temperature profiles is critical for precipitation type predictability. Unfortunately, such information is often limited or sparsely sampled in and around winter storms.
Instead, dual-polarization radar observations offer much greater coverage. To explore the possibility of revealing temperature information using operational radar data, dual-polarization WSR-88D radar data and P-3 aircraft in-situ data collected from all IOPs in 2020 and 2022 during the NASA IMPACTS field campaign are combined. An automated algorithm is developed to determine the distributions of polarimetric radar variables in multiple temperature zones simultaneously being sampled by the P-3 during research flights. The analysis reveals a reliable co-polar correlation coefficient (CC) reduction in the dendritic growth zone (DGZ, -12 °C to -18 °C), as well as in the melting layer (wetbulb temperatures near 0 °C). Increased reflectivity and specific differential phase (KDP) values were found in the temperature zone below the DGZ (-4 °C to -12 °C), which often is dominated by columnar habits, indicating possible secondary ice production and aggregation within the layer. This study explores the KDP distribution and particle properties within the temperature layers favorable for needle and dendrite growth when aggregates are present. The covariability between the enhanced KDP values and other polarimetric variables, including differential reflectivity (ZDR) and CC, within the two temperature layers is explored in the context of the different microphysical processes happening there. P-3-observed particle size distributions show that in both temperature layers, greater number concentrations of 0.8-4.2-mm ice particles with mean projected aspect ratios less than unity may be the primary reason for the enhancement of KDP values. Evidence from the CPI images reveals the complexity of particle shapes and microphysical processes in both temperature zones, and indicates the increased KDP within the -4 °C to -12 °C temperature zone may not only be a result of large number concentration of pristine needles. Through this study, connections are built between temperature ranges, particle habits, and polarimetric radar variables, with an eye towards polarimetric radar data assimilation to leverage this information and contribute to forecast improvements in winter storms.
Instead, dual-polarization radar observations offer much greater coverage. To explore the possibility of revealing temperature information using operational radar data, dual-polarization WSR-88D radar data and P-3 aircraft in-situ data collected from all IOPs in 2020 and 2022 during the NASA IMPACTS field campaign are combined. An automated algorithm is developed to determine the distributions of polarimetric radar variables in multiple temperature zones simultaneously being sampled by the P-3 during research flights. The analysis reveals a reliable co-polar correlation coefficient (CC) reduction in the dendritic growth zone (DGZ, -12 °C to -18 °C), as well as in the melting layer (wetbulb temperatures near 0 °C). Increased reflectivity and specific differential phase (KDP) values were found in the temperature zone below the DGZ (-4 °C to -12 °C), which often is dominated by columnar habits, indicating possible secondary ice production and aggregation within the layer. This study explores the KDP distribution and particle properties within the temperature layers favorable for needle and dendrite growth when aggregates are present. The covariability between the enhanced KDP values and other polarimetric variables, including differential reflectivity (ZDR) and CC, within the two temperature layers is explored in the context of the different microphysical processes happening there. P-3-observed particle size distributions show that in both temperature layers, greater number concentrations of 0.8-4.2-mm ice particles with mean projected aspect ratios less than unity may be the primary reason for the enhancement of KDP values. Evidence from the CPI images reveals the complexity of particle shapes and microphysical processes in both temperature zones, and indicates the increased KDP within the -4 °C to -12 °C temperature zone may not only be a result of large number concentration of pristine needles. Through this study, connections are built between temperature ranges, particle habits, and polarimetric radar variables, with an eye towards polarimetric radar data assimilation to leverage this information and contribute to forecast improvements in winter storms.
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