Quantitative Investigations of the Unprecedented Stratospheric Ozone Depletion During Spring 2020 in the Arctic

The severe depletion of Arctic lower stratospheric (ALS) ozone in spring 2020 has attracted considerable attention. However, the dynamic and chemical contributions of various source regions to ALS ozone levels in spring 2020 remains unclear. To enhance our understanding of Arctic stratospheric ozone, in this study, we used tagged ozone tracers from the specified dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) to quantify the dynamic and chemical contributions from different source regions to the ALS ozone levels in the winter and spring of 2019/2020. The SD-WACCM simulation results indicated that the recovery of ozone after warming of the ALS (April 19-May 19) mainly occurred due to advective transport. The northern mid-latitudinal lower stratosphere and tropical lower stratosphere had the largest advective contributions to the ALS ozone, with 49.71 and 31.00 DU, respectively. Compared with other years, the combination of an unusually weak dynamic ozone supply and severe chemical depletion contributed to the record-low ALS ozone in spring 2020. The persistent and strong polar vortex before the warming (March 18-April 18) resulted in an unusually weak ozone supply, whereas ozone from lower latitudes was gradually transported to the Arctic after the warming. Clear chlorine and bromine activations were simulated during the winter-spring of 2019/2020, and bromine activation continued until June, leading to severe ozone chemical depletion. Our findings can be used to enhance predictions of low ozone events within the Arctic in future years and enhance future research on Arctic stratospheric ozone. sd-waccm-o3.nc, sd-waccm-T.nc, and o3-halogen.nc are average ozone, temperature, and halogen profiles over the Arctic, respectively. map-sd-waccm-o3.nc is average ozone mixing ratios from SD-WACCM in the Arctic region in Interval 1. The plotted ipynb code runs on python version 3.8.8. The data.xlsx includes six sheets. Sheet1 is daily total advective and chemical tendencies. Sheet2 is cumulative advective and chemical tendencies of ozone tracers in the seven source regions of the ALS in Intervals 1 and 2. Sheet3 is daily total advective and chemical tendencies in 2005, 2006, 2009,2011 and 2020. Sheet4 is average O3, ClO, BrO mixing ratios at 70 hPa in the Arctic and the severely ozone-depleted region. Sheet5 is average contributions of the seven regions to ALS ozone. Sheet6 is cumulative advective and chemical tendencies of ozone tracers in the seven source regions of the severely ozone-depleted region lower stratosphere in Intervals 1 and 2.

2020年春季北极平流层下层（Arctic lower stratospheric，以下简称ALS）臭氧的严重耗竭引发了广泛关注。然而，目前仍未明确不同源区对2020年春季ALS臭氧水平的动力与化学贡献。为加深对北极平流层臭氧的科学认知，本研究借助指定动力学版本全大气社区气候模式（Whole Atmosphere Community Climate Model, SD-WACCM）的标记臭氧示踪剂，量化了2019/2020年冬春季不同源区对ALS臭氧水平的动力与化学贡献。
SD-WACCM模拟结果显示，2020年北极平流层下层升温时段（4月19日至5月19日）的臭氧恢复主要由平流输送过程主导。北半球中纬度平流层下层与热带平流层下层对ALS臭氧的平流贡献最大，分别达49.71多布森单位（Dobson Unit, DU）与31.00 DU。与其他年份相比，异常偏弱的动力臭氧供给与严重的化学臭氧耗竭共同作用，造就了2020年春季创纪录的ALS臭氧低值。升温前（3月18日至4月18日）持续且强劲的极涡导致臭氧供给异常偏弱，而升温后低纬度臭氧逐步向北极区域输送。
本研究在2019/2020年冬春季模拟得到了显著的氯、溴活化过程，且溴活化持续至6月，进而引发了严重的臭氧化学耗竭。本研究结果可用于提升未来北极低臭氧事件的预测能力，并推动后续北极平流层臭氧相关研究。
sd-waccm-o3.nc、sd-waccm-T.nc与o3-halogen.nc分别为北极区域的平均臭氧、温度与卤素廓线数据；map-sd-waccm-o3.nc为区间1内北极区域SD-WACCM模拟的平均臭氧混合比数据。本次绘图所用的ipynb代码可在Python 3.8.8版本环境下运行。data.xlsx包含6个工作表：工作表1为逐日总平流输送与化学倾向；工作表2为区间1与区间2内，北极平流层下层7个源区臭氧示踪剂的累积平流输送与化学倾向；工作表3为2005、2006、2009、2011与2020年的逐日总平流输送与化学倾向；工作表4为北极与严重臭氧耗竭区域70 hPa高度处的平均O3、ClO、BrO混合比；工作表5为7个源区对ALS臭氧的平均贡献；工作表6为区间1与区间2内，严重臭氧耗竭区域平流层下层7个源区臭氧示踪剂的累积平流输送与化学倾向。