NOAA/WDS Paleoclimatology - Williamson County, Texas Glacial Stalactite Stable Isotope Data

Thunderstorms in the Southern Great Plains of the United States are among the strongest on Earth and have been shown to be increasing in intensity and frequency during recent years. Assessing changes in storm characteristics under different climate scenarios, however, remains highly uncertain due to limitations in climate model physics. We analyse oxygen isotopes from Texas stalactites from 30-50 thousand years ago to assess past changes in thunderstorm size and duration using a modern radar-based calibration for the region. Storm regimes shift from weakly to strongly organized on millennial timescales and are coincident with well-known abrupt climate shifts during the last glacial period. Modern-day synoptic analysis suggests that thunderstorm organization in the Southern Great Plains is strongly coupled to changes in large-scale wind and moisture patterns. These changes in the large-scale circulation may be used to assess future predictions and palaeo-simulations of mid-latitude thunderstorm climatologies.

美国南部大平原（Southern Great Plains）的雷暴属于全球最强的雷暴类型之一，近年研究证实其强度与发生频次均呈上升态势。然而，受限于气候模式物理过程的固有局限，不同气候情景下雷暴特征变化的评估仍存在高度不确定性。本研究依托该区域基于现代雷达构建的校准方法，对距今3万至5万年的德克萨斯州钟乳石中的氧同位素展开分析，以此反推过去雷暴的规模与持续时间变化。雷暴活动模态在千年尺度上从弱组织化向强组织化转变，且与末次冰期期间广为人知的突发性气候转型事件高度吻合。现代天气学分析表明，美国南部大平原的雷暴组织化程度与大尺度风场及水汽格局的变化存在显著耦合关系。上述大尺度环流变化可用于评估中纬度雷暴气候学的未来预测结果与古气候模拟结果。