This study identified a prominent temporal seesaw haze intensity case that occurred between the late winter months of 2010 in the North China Plain (NCP), featuring considerably suppressed haze intensity in January and enhanced haze intensity in the adjacent month of February in 2011. We suggest that dramatic alternations of atmospheric and oceanic anomalies played fundamental roles in forming this seesaw haze intensity case, rather than changes in manmade emission anomalies. The suppressed haze intensity in January 2011 was tied to an equivalent barotropic cyclonic anomaly that dominated the NCP and its surroundings, which generated in situ haze-suppressed meteorology characterized by strengthened lower-level northerly anomalies with cold and dry conditions, as well as elevated boundary layer height and destabilized atmospheric stratification. In stark contrast, the enhanced haze intensity in February 2011 was connected to an equivalent barotropic anticyclonic anomaly, linking a haze-favourable meteorology opposite to that in January 2011. The pronounced North Atlantic sea surface temperature (SST) tripole anomalies, with positive anomalies in the tropical and mid-latitudinal North Atlantic and negative anomalies in the subtropical North Atlantic, made a significant contribution to the above-mentioned seesaw haze intensity case. Diagnostic analyses suggested that the January North Atlantic SST tripole anomalies were linked to a significant negative North Atlantic Oscillation (NAO)-like pattern, which acted as the source of the Rossby wave train to generate concurrent haze-suppressed meteorology over the NCP. In February, although the NAO-like pattern was drastically dampened, the enhanced barotropic cyclonic anomaly centred southeast of the Yamal Peninsula played a critical role in relaying the impact of January tripole SST anomalies, thus inducing concurrent haze-favourable meteorology. Consequently, January North Atlantic SST tripole anomalies could exert an effective modulation effect on the generation of seesaw haze intensity. The proposed mechanism was further verified using the Community Earth System Model Large Ensemble Numerical Simulation (CESM-LENS) datasets.

中文翻译：

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北大西洋海温三极异常对华北平原冬末期间锯齿形霾强度的潜在远程强迫：案例研究

本研究确定了华北平原 (NCP) 2010 年冬末期间发生的一次显着的时间跷跷板霾强度案例，其特点是 2011 年 1 月份霾强度显着抑制，而邻近的 2 月份霾强度则增强。我们建议大气和海洋异常的剧烈变化在形成这种锯齿形雾霾强度情况中发挥了重要作用，而不是人为排放异常的变化。2011年1月受抑制的霾强度与主导NCP及其周边地区的同等正压气旋异常有关，该异常产生了原位霾抑制气象，其特征是寒冷和干燥条件下的低层北风异常增强以及边界升高层高和不稳定的大气层结。与此形成鲜明对比的是，2011 年 2 月增强的雾霾强度与等效的正压反气旋异常有关，将与 2011 年 1 月相反的有利于雾霾的气象联系起来。北大西洋海面温度 (SST) 三极异常明显，其中正异常北大西洋热带和中纬度区域以及北大西洋副热带区域的负异常对上述雾霾强度的跷跷板现象做出了重大贡献。诊断分析表明，1 月北大西洋海温三极异常与显着的负北大西洋涛动 (NAO) 样模式有关，该模式是罗斯贝波列的来源，在 NCP 上空产生同时的雾霾抑制气象。2月份，虽然类似NAO​​的模式大幅减弱，以亚马尔半岛东南部为中心的增强的正压气旋异常在传递1月三级海温异常的影响中发挥了关键作用，从而引发了同时出现的有利于霾的气象。因此，1月份北大西洋海温三极异常可以对跷跷板霾强度的产生产生有效的调节作用。使用社区地球系统模型大型集合数值模拟（CESM-LENS）数据集进一步验证了所提出的机制。