ERA5再分析与CAM6模拟中北美强局地风暴环境及天气尺度特征的气候学
Climatology of severe local storm environments and synoptic-scale features over North America in ERA5 reanalysis and CAM6 simulation
AI总结：
本研究对比ERA5再分析与CAM6模拟，评估北美强局地风暴环境及天气尺度特征的气候学再现能力，发现两者均能有效重现其时空分布与关键特征。
摘要：
已知强局地风暴（SLS）活动发生在特定的热力学和动力学环境中。这些环境通常与关键的天气尺度特征相关——包括大平原南部低空急流、干线、抬升混合层和温带气旋——这些特征将大尺度气候与SLS环境联系起来。本研究分析了1980年至2014年间北美地区ERA5再分析数据和社区大气模型版本6（CAM6）中环境参数和天气尺度特征的时空分布。与无线电探空仪相比，ERA5成功再现了SLS环境，具有强时空相关性和低偏差，尤其是在大平原地区。ERA5和CAM6均再现了美国中部SLS环境的气候学特征及其强烈的季节和日变化周期。ERA5和CAM6也再现了天气尺度特征的气候学发生频率，其分布模式与SLS环境的分布模式相似。与ERA5相比，CAM6在美国东部地区的对流有效位能（CAPE）表现出高偏差，主要归因于地表湿度的偏高，其次是风暴相对螺旋度（SRH）因低层风增强而偏高。合成分析表明，在ERA5和CAM6中，美国东部大部分地区存在有利于显著SLS环境的一致天气异常模式，但美国东南部的模式有所不同。总体而言，结果表明ERA5和CAM6均能够再现SLS环境以及产生这些环境的天气尺度特征和瞬变事件。
英文摘要：
Severe local storm (SLS) activity is known to occur within specific thermodynamic and kinematic environments. These environments are commonly associated with key synoptic-scale features--including southerly Great Plains low-level jets, drylines, elevated mixed layers, and extratropical cyclones--that link the large-scale climate to SLS environments. This work analyzes spatiotemporal distributions of both the environmental parameters and synoptic-scale features in ERA5 reanalysis and in Community Atmosphere Model version 6 (CAM6) during 1980--2014 over North America. Compared to radiosondes, ERA5 successfully reproduces SLS environments, with strong spatiotemporal correlations and low biases, especially over the Great Plains. Both ERA5 and CAM6 reproduce the climatology of SLS environments over the central United States as well as its strong seasonal and diurnal cycles. ERA5 and CAM6 also reproduce the climatological occurrence of the synoptic-scale features, with the distribution pattern similar to that of SLS environments. Compared to ERA5, CAM6 exhibits a high bias in Convective Available Potential Energy over the eastern United States primarily due to a high bias in surface moisture, and to a lesser extent, storm-relative helicity due to enhanced low-level winds. Composite analysis indicates consistent synoptic anomaly patterns favorable for significant SLS environments over much of the eastern half of the United States in both ERA5 and CAM6, though the pattern differs for the southeastern United States. Overall, results indicate that both ERA5 and CAM6 are capable of reproducing SLS environments as well as the synoptic-scale features and transient events that generate them.
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