The Arctic middle atmosphere was affected by major sudden stratospheric warmings (SSW) in February 2018 and January 2019, respectively. In this article, we report for the first time the impact of these two events on the middle atmospheric nitric oxide (NO) abundance. The study is based on measurements obtained during two dedicated observation campaigns, using the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite, measuring NO globally since 2003. The SSW of February 2018 was similar to other, more dynamically quiet, Arctic winters in term of NO downward transport from the upper mesosphere–lower thermosphere to lower altitudes (referred to as energetic particle precipitation indirect effect EPP-IE). On the contrary, the event of January 2019 led to one of the strongest EPP-IE cases observed within the Odin operational period. Important positive NO anomalies were indeed observed in the lower mesosphere–upper stratosphere during the three months following the SSW onset, corresponding to NO volume mixing ratios more than 50 times higher than the climatological values. These different consequences on the middle atmospheric composition are explained by very different dynamical characteristics of these two SSW events.

北极中层大气分别于2018年2月和2019年1月受到平流层突然强烈变暖的影响。在本文中，我们首次报告了这两个事件对中层大气一氧化氮（NO）含量的影响。这项研究基于在两次专门的观察​​运动中获得的测量结果，这些运动是使用Odin卫星上的亚毫米辐射计（SMR），自2003年以来在全球范围内进行NO测量。2018年2月的SSW与2005年2月其他北极地区更为活跃，安静的冬季相似。 NO从上层中层层-下层热层向下传输到较低高度的术语（称为高能粒子沉淀间接效应EPP-IE）。相反，2019年1月的事件导致在Odin运营期内观察到的最强的EPP-IE案件之一。在南半球爆发后的三个月中，在中低层平流层上部确实发现了重要的正NO异常，这对应于NO体积混合比比气候值高50倍以上。这两个西南偏南事件的动力学特征非常不同，可以解释这些对中间大气成分的不同后果。