Scientific motivation, and co-ordination of HALO campaign ASCCI and provision of quality controlled merged data products

ASCCI项目是在北方半球极地冬末至早春期间进行的一项HALO使命，这是为了继续利用HALO飞机进行极地臭氧测量活动而提出的。其中最值得注意的是两项光环飞行任务，即南半球的SOUTHTRAC和北方半球的POLSTRACC。特别是北方半球在极地平流层动态方面显示出非常大的年与年之间的变化，因此在极地臭氧方面也是如此。第一次北极极地臭氧相关测量活动POLSTRACC于2015/2016年冬季进行，该冬季的特点是创纪录的低温，直到仲冬，随后是2016年2月平流层突然变暖。因此，我们建议在北方半球进行第二次极地冬季活动，以调查北方半球高纬度地区极涡和臭氧的动力学演变。正如提案中详细说明的那样，最近Von der Gathen等人也证明了这一点，（2021年），预计气候变化将有利于北极地区今后出现大量季节性臭氧损失。因此，必须定期重访北极平流层下部，并调查不断变化的大气层中的臭氧损失情况。与中纬度地区相反，模拟极地对流层臭氧一般显示出明显的低偏差。有人认为，这可能是由于化学（例如对流层污染水平和平流层的NOy流入）以及富含臭氧的平流层空气的输送导致了这些差异。虽然我们建议研究极地涡旋及其化学演变，ASCCI将有一个稍微更强的重点对中纬度和北极对流层的影响。特别是极地臭氧损失对春季中纬度臭氧的影响以及北极对流层上部的化学组成，以及这与平流层的迁移和对流层污染的联系程度，将是南极气候倡议的一个重点。在本提案中，我们申请与活动协调相关的费用以及与制作最终质量受控合并数据相关的费用，其中包括所有观测数据以及气象和模型数据。

The project ASCCI is a HALO mission in the Northern Hemisphere polar late winter to early spring which is proposed in the continuation of polar ozone measurement campaigns conducted with the HALO aircraft. Most notably these are the two HALO missions SOUTHTRAC in the Southern Hemisphere and POLSTRACC in the Northern Hemisphere. Especially the Northern Hemisphere shows very large year to year variability in polar stratospheric dynamics and therefore also in polar ozone. The first Arctic polar ozone related measurement campaign POLSTRACC took place in the winter 2015/2016, a winter characterized by record low temperatures until mid winter followed by a sudden stratospheric warming in February 2016. We therefore propose to perform a second polar winter campaign in the Northern Hemisphere to investigate the evolution of the dynamics of the polar vortex and ozone in the Northern Hemisphere high latitudes. As detailed in the proposal, and recently shown by Von der Gathen et al., (2021), climate change is expected to favour large seasonal loss of ozone in the Arctic in the future. It will thus be of importance to regularly revisit the Arctic lower stratosphere and investigate the ozone loss in a changing atmosphere. In contrast to mid-latitudes, modelled polar tropospheric ozone generally shows a significant low bias. It has been argued that this could be due both to chemistry (e.g. levels of tropospheric pollution and NOy influx from the stratosphere) as well as transport of ozone rich stratospheric air cold contribute to these discrepancies. While we propose to study the polar vortex and its chemical evolution, ASCCI will have a slightly stronger emphasis on the implications for the mid latitudes and for the Arctic troposphere. In particular the impact of polar ozone loss on spring time mid latitude ozone will be a focus of ASCCI as well as the chemical composition of the upper Arctic troposphere and in how far this can be linked to transport from the stratosphere and to tropospheric pollution. In this proposal we apply for the costs associated with the coodination of the campaign and costs associated for the production of final quality controlled merged data which include all observational data as well as meteorological and model data.