A Feature-Based Approach to Classifying Summertime Potential Vorticity Streamers Linked to Rossby Wave Breaking in the North Atlantic Basin
A Feature-Based Approach to Classifying Summertime Potential Vorticity Streamers Linked to Rossby Wave Breaking in the North Atlantic Basin
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DOI：
10.1175/jcli-d-19-0812.1
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发表时间：
2020-07
影响因子：
4.9
通讯作者：
P. Papin;L. Bosart;R. Torn
中科院分区：
文献类型：
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作者：
P. Papin;L. Bosart;R. Torn
本文研究了与罗斯比破波（RWB）相关的气候位涡流（PVS）活动，它可以通过湿度和风异常影响副热带北大西洋（NATL）盆地的TC活动。在350-K等熵表面上沿2-PVU （1 PVU = 10−6 K kg−1 m2 s−1）轮廓识别PVSs，使用结合先前方法的独特识别技术。从1979-2015年6 - 11月的ERAI气候数据中，共鉴定出21 149个PVS个体，其中7 - 8月为峰值。由于新技术确定了更广泛的病例，因此在本研究中确定的PVS总数超过了该地区以前的PVS气候学。PVS大小和强度的变化促使新的PVS活性指数（PVSI）的发展，该指数提供了PVS活性的综合衡量标准，可以改善与TC活性的比较。例如，相对于PVS频率、大小或强度，PVSI与季节性TC活动有更强的负相关（r = - 0.55）。6 - 7月的PVSI与8 - 11月的PVSI也呈正相关（r = 0.67），表明具有预测能力。与ERAI和日本气象厅55年再分析（JRA-55）气候学相比，气候预报系统再分析（CFSR）中的pws数量较多，但平均强度总体较弱。虽然在ERAI和JRA-55气候学中没有观测到PVSI的长期趋势，但在CFSR中观测到PVSI的负趋势，这可能与CFSR和ERAI数据集在气候期早期（1979-86）近对流层顶静稳定性的差异有关。
This study examines climatological potential vorticity streamer (PVS) activity associated with Rossby wave breaking (RWB), which can impact TC activity in the subtropical North Atlantic (NATL) basin via moisture and wind anomalies. PVSs are identified along the 2-PVU (1 PVU = 10−6 K kg−1 m2 s−1) contour on the 350-K isentropic surface, using a unique identification technique that combines previous methods. In total, 21 149 individual PVS instances are identified from the ERA-Interim (ERAI) climatology during June–November over 1979–2015 with a peak in July–August. The total number of PVSs identified in this study is more than previous PVS climatologies for this region, since the new technique identifies a wider range of cases. Variations in PVS size and intensity prompt the development of a new PVS activity index (PVSI), which provides an integrated measure of PVS activity that can improve comparisons with TC activity. For instance, PVSI has a stronger negative correlation with seasonal TC activity (r = −0.55) relative to PVS frequency, size, or intensity alone. PVSI in June–July is also positively correlated with PVSI in August–November (r = 0.67), suggesting predictive capability. Compared to the ERAI and Japan Meteorological Agency 55-Year Reanalysis (JRA-55) climatology, there are more PVSs in the Climate Forecast System Reanalysis (CFSR) but these have weaker average intensity overall. While no long-term trend in PVSI is observed in the ERAI or JRA-55 climatologies, a negative trend is observed in CFSR, which could be related to differences in near tropopause static stability early in the climatological period (1979–86) between the CFSR and ERAI datasets.