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摘要: 基于南极中山站1993-2023年Brewer光谱仪观测大气臭氧总量（TOC），对再分析数据Merra2和ERA5的TOC进行验证、评估和趋势分析。结果表明，1）再分析数据与地基测值在反映南极“臭氧洞”现象及TOC季节变化均一致。 日均 Merra2和ERA5的TOC差异(∆TOC （DU）)分别为-2.0±9.6DU和3.2±7.8DU；相对差异(∆TOC(%))概率分布均呈随机特征且中心值分别为-0.69%和1.5%（P<0.0001）。2）在1993-2004年和2005-2023年两个时段的“臭氧洞（地基TOC≤220DU）”期间, Merra2的∆TOC（%）均值先后分别为6.9%±4.6%（1σ）和-0.4%±2.3%，而ERA5则分别为4.6%±2.0%（1σ）和6.4%±3.1%(1σ)；在非“臭氧洞”期间两者对应均值都在±2%以内；随太阳天顶角（SZA）上升，Merra2 和ERA5的∆TOC（%）在1993-2004年分别呈现3%和2%上升、而在2005-2023年则分别呈-2%下降和2%上升;2005-2023年的再分析TOC数据质量优于1993-2004年;Merra2在2005年以后系统地低于地基TOC值，最低可达6%以上，而ERA5在2012年则系统地高于地基TOC高值。3）经Brewer测值订正后的再分析数据均一致地展现出中山站TOC恢复态势，其中ERA5的恢复速率是 1.3DU/10a。研究建议再分析数据在被地基验证和订正之前应慎用于评估南极TOC长期变化趋势。地基TOC观测时数虽然受SZA或天气的影响而远低于再分析数据，但对再分析数据的验证是评估TOC长期变化的关键依据。Abstract:
Based on the Brewer ozone spectrophotometer long-term (1993-2023) observations at Zhongshan Station, Antarctica, atmospheric total ozone column (TOC) of the Merra2 and ERA5 reanalysis are compared, evaluated and their trends are analyzed The results show that the reanalysis are generally in a good agreement with the ground-based data in the context of occurrence of the ‘ozone hole’ and the TOC seasonality The TOC bias (∆TOC (DU)) and relative difference (∆TOC(%)) on the daily mean scale are -2 0±9 6(1σ)DU and -0 6±4 3%(1σ) for Merra2 and -0 6±4 3%(1σ) for ERA5 respectively Both the probability distribution of ∆TOC(%)s exhibit each normal random processes and their large variations occurred at the end of March and during the ‘ozone hole’ period The reanalysis data were divided into two periods, 1993-2004 and 2005-2023, based on the changes of satellites to which the reanalysis data were assimilated, but the ∆TOC(%) values (including ERA5) during the ‘ozone hole’ increases with decreasing of the TOC in both periods, and the ∆TOC(%) values for Merra2/ERA5 were respectively 6 9%±4 6%(1σ)/4 6%±2 0%(1σ) and -0 4%~2 3%(1σ)/ 6 4%±3 1%(1σ) Whereas the corresponding averages for the non-ozone hole periods were respectively of only 0 3% ± 1 5% (1σ)/0 6% ± 1 4% (1σ) The ∆TOC (%) of Merra2 and ERA5 show an increasing trend with the solar zenith angle (SZA) during 1993 -2004, with each magnitude of 3% and 2%, while the opposite trend is observed from 2005 to 2023, with magnitude of -2% and 2% respectively for Merra2 and ERA5 Merra2 (ERA5) is systematically lower (higher) than the observed TOC after 2005 (2012), with ∆TOC (%) as low(high) as more than 6% Both the ERA5 and Brewer data show a clear TOC recovery trend during the last 30 years of the ‘ozone hole’ periods whereas neither of them is characterized by a clear trend during the last 31 years of the non-ozone hole periods Correspondingly, the data of Merra2 exhibits clear TOC deletion trends Both the reanalysis TOC data validated by Brewer's observation show their consistent recovery trends of TOC, and the recovering rate of ERA5 is 1 3 DU/10a The study suggests that raw reanalysis TOC data should be used with much caution before evaluating the long-term trends of the ozone layer, and the data from the ground-based observations, albeit the number is much lower than that of reanalysis outputs due to seasonal SZA or weather conditions, is critical for the reanalysis TOC validation and conclusions of TOC trend
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Key words:
- total ozone (TOC) /
- Merr2-TOC /
- ERA5-TOC /
- Brewer spectrophotometer /
- Zhongshan Station
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