The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtai...The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data.The results are verified by a supercell storm process.1)The modified HSDA improves the identification of large hail and giant hail.The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails,the dynamic and microphysical characteristics for supercell,and the real situation.2)The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells.Small hail first forms at the suspension echo,then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts,colliding with the abundant supercooled water in the KDP column.Finally,large hail and giant hail fall near the direction of the updrafts to form a strong echo wall,and giant hail falls 6–12 km from the central updraft.3)The maxima of the ZDR and KDP columns can be used to predict the hail-growth trend,which exceeds the−20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm.When hail falls to the ground,the ZDR column shortens and the KDP column disappears,which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.展开更多
The growth trajectory of hailstones in clouds determines the ground intensity and spatial distribution of hailfall.A systematic study of hail trajectories can help improve the current scientific understanding of the m...The growth trajectory of hailstones in clouds determines the ground intensity and spatial distribution of hailfall.A systematic study of hail trajectories can help improve the current scientific understanding of the mechanisms by which hail forms in semi-arid regions of China and,in doing so,improve the quality of hail forecasts and warnings and help to prevent and mitigate disasters.In this study,the WRFv3.7.1 model was employed to provide the background field to drive the hailstone trajectory model.Cluster analysis was then used to classify hail trajectories to investigate the characteristics of different types of hail trajectories and the microphysical characteristics of hail formation.The differences in hail trajectories might be mainly due to differences in the background flow fields and microphysical fields of hail clouds in different regions.Comparative analysis revealed that as the maximum particle size of ground hailfall increased,the maximum supercooled cloud water content and the maximum updraft velocity for the formation and growth of hailstone increased.The larger the size when the hailstone reaches its maximum height,the larger the ground hailstone formed.Overall,the formation and growth of hailstone are caused by the joint action of the dynamical flow field and cloud microphysical processes.The physical processes of hailstone growth and main growth regions differ for different types of hail trajectories.Therefore,different catalytic schemes should be adopted in artificial hail prevention operations for different hail clouds and trajectories due to differences in hail formation processes and ground hailfall characteristics.展开更多
基金supported by the Shandong Provincial Natural Science Foundation of China(Nos.ZR2020MD052 and ZR2022MD072)the National Natural Science Foundation of China(Grant No.41675029)+2 种基金East China Regional Collaborative Innovation Fund for Meteorological Science and Technology(No.QYHZ202101)Project of Xiamen Bureau of Science and Technology(No.3502Z20214ZD4005)Key Project of Shandong Meteorological Bureau(Nos.2021SDQXZ09 and SDLD2022-02)。
文摘The hail size discrimination algorithm(HSDA)and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars.A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data.The results are verified by a supercell storm process.1)The modified HSDA improves the identification of large hail and giant hail.The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails,the dynamic and microphysical characteristics for supercell,and the real situation.2)The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells.Small hail first forms at the suspension echo,then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts,colliding with the abundant supercooled water in the KDP column.Finally,large hail and giant hail fall near the direction of the updrafts to form a strong echo wall,and giant hail falls 6–12 km from the central updraft.3)The maxima of the ZDR and KDP columns can be used to predict the hail-growth trend,which exceeds the−20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm.When hail falls to the ground,the ZDR column shortens and the KDP column disappears,which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41975176, 42061134009)the High Performance Computing Center of Nanjing University of Information Science and Technology for their support of this work
文摘The growth trajectory of hailstones in clouds determines the ground intensity and spatial distribution of hailfall.A systematic study of hail trajectories can help improve the current scientific understanding of the mechanisms by which hail forms in semi-arid regions of China and,in doing so,improve the quality of hail forecasts and warnings and help to prevent and mitigate disasters.In this study,the WRFv3.7.1 model was employed to provide the background field to drive the hailstone trajectory model.Cluster analysis was then used to classify hail trajectories to investigate the characteristics of different types of hail trajectories and the microphysical characteristics of hail formation.The differences in hail trajectories might be mainly due to differences in the background flow fields and microphysical fields of hail clouds in different regions.Comparative analysis revealed that as the maximum particle size of ground hailfall increased,the maximum supercooled cloud water content and the maximum updraft velocity for the formation and growth of hailstone increased.The larger the size when the hailstone reaches its maximum height,the larger the ground hailstone formed.Overall,the formation and growth of hailstone are caused by the joint action of the dynamical flow field and cloud microphysical processes.The physical processes of hailstone growth and main growth regions differ for different types of hail trajectories.Therefore,different catalytic schemes should be adopted in artificial hail prevention operations for different hail clouds and trajectories due to differences in hail formation processes and ground hailfall characteristics.
