Influence of Low‐Frequency PNA Variability on MJO Teleconnections to North American Atmospheric River Activity
Influence of Low‐Frequency PNA Variability on MJO Teleconnections to North American Atmospheric River Activity
复制标题
DOI：
10.1029/2021gl094078
复制
发表时间：
2021-07
影响因子：
5.2
通讯作者：
Kinya Toride;G. Hakim
中科院分区：
文献类型：
--
作者：
Kinya Toride;G. Hakim
马登-朱利安振荡（MJO）调制了沿着北美西海岸的大气河流（AR）活动。仅基于MJO阶段的AR预测技能是有限的，从而激发了其他预测因素的识别。在这里，我们表明太平洋/北美（PNA）模式的低频变率主要与MJO无关，并且每月PNA模式对MJO-AR关系的影响比其他大尺度模式（如厄尔尼诺南方涛动和准两年振荡）更强。在PNA+条件下，当太平洋急流出口区域位于比平均水平更靠东的位置时，斜压波包向下游延伸到北美。波包纬向尺度的明显对比导致了活跃和非活跃AR相位的划分。PNA的影响是最显着的北美西北太平洋地区，AR登陆最频繁，与隐含的预测技巧超过20天。
The Madden‐Julian oscillation (MJO) modulates atmospheric river (AR) activity along the West Coast of North America. The forecast skill of ARs based solely on the MJO phase is limited, motivating the identification of other predictive factors. Here we show that low‐frequency variability of the Pacific/North American (PNA) pattern is mostly independent of the MJO, and the monthly PNA pattern influences the MJO‐AR relationship much more robustly than other large‐scale patterns such as the El Niño Southern Oscillation and the quasi‐biennial oscillation. During PNA+ conditions, when the Pacific jet exit region is located further east than average, baroclinic wave packets extend downstream toward North America. The clear contrast in wave packets' zonal scale results in partitioning active and inactive AR phases. The PNA influence is most significant over the Pacific Northwest region of North America, where AR landfall is most frequent, with implied forecasting skill beyond 20 days.