Differing Trends in United States and European Severe Thunderstorm Environments in a Warming Climate
Differing Trends in United States and European Severe Thunderstorm Environments in a Warming Climate
复制标题
DOI：
10.1175/bams-d-20-0004.1
复制
发表时间：
2020-09
影响因子：
8
通讯作者：
M. Taszarek;J. Allen;H. Brooks;Natalia Pilguj;B. Czernecki
中科院分区：
文献类型：
--
作者：
M. Taszarek;J. Allen;H. Brooks;Natalia Pilguj;B. Czernecki
支持大气对流的环境的历史频率的长期趋势尚不清楚，只是部分地遵循气候变暖的预期。这种不确定性是由于严重雷暴的成分缺乏明确的变化（即，条件不稳定、足够的低层湿度、引发机制和垂直风切变）。ERA5混合西格玛数据允许包括对流抑制在内的热力学参数的上级表征，这对低对流层中的水平数量非常敏感。使用每小时的数据，我们表明，长期的不稳定性和较强的对流抑制的减少，导致在美国南部的雷暴环境的频率下降，特别是在夏季。相反，在整个东南部的冬季，观察到龙卷风的有利条件越来越多。在欧洲，一个显着的几十年来增加低层水分提供了积极的趋势，雷暴环境在南部，中部和北部，减少了东部由于加强对流抑制。在欧洲西北部和大平原上观察到垂直风切变和风暴相对螺旋度的适度增加。这两个大陆都表现出负面的趋势，在部分环境可能对流启动。这表明，尽管不稳定性增加，但由于对流抑制较强和相对湿度较低，气候变暖中的雷暴可能不太可能发展。对流开始和由此产生的降水的减少可能对农业、水的可用性以及大冰雹和龙卷风等恶劣天气的频率产生长期影响。我们的研究结果还表明，在美国观察到的趋势不能被认为是其他大陆的代表。
Long-term trends in the historical frequency of environments supportive of atmospheric convection are unclear, and only partially follow the expectations of a warming climate. This uncertainty is driven by the lack of unequivocal changes in the ingredients for severe thunderstorms (i.e., conditional instability, sufficient low-level moisture, initiation mechanism, and vertical wind shear). ERA5 hybrid-sigma data allow for superior characterization of thermodynamic parameters including convective inhibition, which is very sensitive to the number of levels in the lower troposphere. Using hourly data we demonstrate that long-term decreases in instability and stronger convective inhibition cause a decline in the frequency of thunderstorm environments over the southern United States, particularly during summer. Conversely, increasingly favorable conditions for tornadoes are observed during winter across the Southeast. Over Europe, a pronounced multidecadal increase in low-level moisture has provided positive trends in thunderstorm environments over the south, central, and north, with decreases over the east due to strengthening convective inhibition. Modest increases in vertical wind shear and storm-relative helicity have been observed over northwestern Europe and the Great Plains. Both continents exhibit negative trends in the fraction of environments with likely convective initiation. This suggests that despite increasing instability, thunderstorms in a warming climate may be less likely to develop due to stronger convective inhibition and lower relative humidity. Decreases in convective initiation and resulting precipitation may have long-term implications for agriculture, water availability, and the frequency of severe weather such as large hail and tornadoes. Our results also indicate that trends observed over the United States cannot be assumed to be representative of other continents.