Stratospheric inorganic chlorine (Cl_y) is predominantly released from long-lived chlorinated source gases and, to a small extent, very short-lived chlorinated substances. Cl_y includes the reservoir species (HCl and ClONO₂) and active chlorine species (i.e., ClO_x). The active chlorine species drive catalytic cycles that deplete ozone in the polar winter stratosphere. This work presents calculations of inorganic chlorine (Cl_y) derived from chlorinated source gas measurements on board the High Altitude and Long Range Research Aircraft (HALO) during the Southern Hemisphere Transport, Dynamic and Chemistry (SouthTRAC) campaign in austral late winter and early spring 2019. Results are compared to Cl_y in the Northern Hemisphere derived from measurements of the POLSTRACC-GW-LCYCLE-SALSA (PGS) campaign in the Arctic winter of 2015/2016. A scaled correlation was used for PGS data, since not all source gases were measured. Using the SouthTRAC data, Cl_y from a scaled correlation was compared to directly determined Cl_y and agreed well. An air mass classification based on in situ N₂O measurements allocates the measurements to the vortex, the vortex boundary region, and midlatitudes. Although the Antarctic vortex was weakened in 2019 compared to previous years, Cl_y reached 1687±19 ppt at 385 K; therefore, up to around 50 % of total chlorine was found in inorganic form inside the Antarctic vortex, whereas only 15 % of total chlorine was found in inorganic form in the southern midlatitudes. In contrast, only 40 % of total chlorine was found in inorganic form in the Arctic vortex during PGS, and roughly 20 % was found in inorganic form in the northern midlatitudes. Differences inside the two vortices reach as much as 540 ppt, with more Cl_y in the Antarctic vortex in 2019 than in the Arctic vortex in 2016 (at comparable distance to the local tropopause). To our knowledge, this is the first comparison of inorganic chlorine within the Antarctic and Arctic polar vortices. Based on the results of these two campaigns, the differences in Cl_y inside the two vortices are substantial and larger than the inter-annual variations previously reported for the Antarctic.

中文翻译：

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通过单独的晚冬飞机测量比较南极和北极最低平流层中的无机氯

平流层无机氯 (Cl _y ) 主要从长寿命的氯化源气体中释放出来，在很小的程度上，也从寿命很短的氯化物质中释放出来。Cl _y包括储层物质（HCl 和 ClONO ₂）和活性氯物质（即 ClO _x）。活性氯物质驱动催化循环，消耗极地冬季平流层中的臭氧。这项工作介绍了在南半球晚冬和早春的南半球运输、动力和化学 (SouthTRAC) 活动期间，从高空和远程研究飞机 (HALO) 上的氯化源气体测量值得出的无机氯 (Cl _y ) 的计算2019. 结果与 C _y进行比较来自北半球 2015/2016 年北极冬季 POLSTRACC-GW-LCYCLE-SALSA (PGS) 活动的测量结果。PGS 数据使用了缩放相关性，因为并非所有源气体都被测量。使用SouthTRAC数据，氯_ÿ从缩放的相关进行比较直接测定氯_ÿ和吻合。基于原位 N ₂ O 测量值的空气质量分类将测量值分配给涡旋、涡旋边界区域和中纬度地区。虽然2019年南极涡旋较往年有所减弱，但Cl _y达到1687±19 385 K 处的 ppt；因此，在南极涡旋内发现高达约 50% 的总氯以无机形式存在，而在南部中纬度地区仅发现 15% 的总氯以无机形式存在。相比之下，在 PGS 期间，在北极涡旋中仅发现 40% 的总氯以无机形式存在，而在北中纬度地区发现约 20% 以无机形式存在。两个涡旋内部的差异高达 540 ppt，2019 年南极涡旋中的Cl _y比 2016 年北极涡旋中的C _y多（与当地对流层顶的距离相当）。据我们所知，这是南极和北极极地涡旋中无机氯的首次比较。基于这两个活动的结果，C _y 两个涡旋内部的 变化很大，而且比之前报道的南极年际变化更大。