美国冰雹爆发的季节性及其与天气形势的联系
Seasonality of hail outbreaks in the United States and its link to weather regimes
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中文总结 AI 辅助
研究美国1990 - 2024年冰雹爆发情况，定义冰雹爆发标准，分析其与环境参数关系，发现呈上升趋势，受热力和动力过程影响，利用天气形势建立经验模型捕捉年际变化，首次将冰雹活动与天气形势联系起来。
中文摘要 AI 辅助
美国的冰雹风暴造成了巨大的经济损失，且发生频率似乎呈长期上升趋势。本文对1990年至2024年期间的冰雹活动及相关环境参数进行了更新研究。将冰雹爆发定义为日冰雹报告超过6次（直径≥2英寸），发现1990年以来冰雹爆发呈上升趋势（斜率=0.8天/年），5月、6月及大平原南部增幅最大。环境参数分析表明，冰雹爆发的长期增加与显著冰雹参数（SHIP）的长期增加相关。SHIP的年际变化和长期趋势受热力和动力过程驱动，动力过程在冰雹爆发年际变化中作用更大。利用暖季（4月至7月）天气形势（WRs）发现，大尺度环流调节冰雹爆发频率的年际变化。一个基于WR频率的经验模型能较好地捕捉暖季冰雹爆发的年际变化。本研究首次将冰雹活动与WRs联系起来，有助于更好地理解冰雹爆发的趋势和年际变化。
英文摘要
Hailstorms in the United States produce immense economic losses and have an occurrence frequency that appears to have a long-term positive trend. Here we contribute an updated examination of such hail activity and the relevant environmental parameters over the period 1990--2024. We define a hail outbreak as any day with $\gt 6$ significant hail reports ($hail\geq 2$'' diameter) and find a positive trend in hail outbreaks since 1990 ($slope=0.8$ days $yr^{-1}$) with the largest increases occurring in May and June and in the Southern Great Plains. Analysis of environmental parameters shows that the long-term increase in hail outbreaks correlates with a long-term increase in the significant hail parameter (SHIP, $cc=0.67$, $p\lt 0.01$). The interannual variability and long-term trend of SHIP are driven both by thermodynamic and kinematic processes, though kinematic processes play a more important role than thermodynamic processes in the interannual variability of hail outbreaks. Using warm-season (April--July) weather regimes (WRs), we find that large-scale circulation modulates the interannual variability of hail outbreak frequency. An empirical model using WR frequency captures the interannual variability in warm-season hail outbreaks reasonably well ($cc=0.38$, $p=0.03$). Our study is the first to relate hail activity to WRs and presents a better understanding of the trend and year-to-year variability of hail outbreaks.
