首页 >  2022, Vol. 26, Issue (5) : 971-987

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DOI:

10.11834/jrs.20221413

收稿日期:

2021-06-15

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基于OMI的亚洲地区对流层NO2高分辨率反演产品POMINO v2.1及其与其他产品的定量对比
张宇航1,林金泰1,刘梦瑶2,孔浩1,陈璐璐1,翁宏健1,李春锦1
1.北京大学 物理学院大气与海洋科学系 气候与海气实验室, 北京 100871;2.荷兰皇家气象学会(KNMI), 德比尔特 3731GA
摘要:

对流层二氧化氮(NO2)是一种重要的痕量污染气体。现有基于OMI卫星探测器、覆盖亚洲地区的NO2公开产品QA4ECV、OMNO2和POMINO受到广泛使用,然而对于这3个产品的差异的定量认识仍然不足。我们将前期开发的POMINO产品进行了改进和优化,更新至v2.1并将反演区域扩大至覆盖东亚、东南亚和南亚大部分地区,随后定量分析了QA4ECV、OMNO2 v4和POMINO v2.1对流层NO2垂直柱浓度在2015年—2020年在不同采样条件下的异同。结果显示,POMINO版本的更新对自身NO2柱浓度反演结果的整体影响较小(<10%)。当3个产品均基于POMINO v2.1进行一致采样时,产品之间在整个亚洲区域的平均差异约为10%,在京津冀等污染地区的差异最高可达40%。3个产品均显示,京津冀地区NO2柱浓度在五年间下降了约30%,而长三角地区的变化趋势较小。当3个产品进行分别采样时,POMINO v2.1的有效数据量比其他两个产品增加了11%—44%,特别是更好地保留了重污染情形下的NO2数据,从而降低了采样引起的对NO2污染水平的系统性低估。本研究对于NO2卫星产品差异的定量分析有助于认识氮氧化物污染状况以及排放和影响评估。

High-resolution Tropospheric NO2 Retrieval over Asia based on OMI POMINO v2.1 and quantitative comparison with other products
Abstract:

Nitrogen dioxide (NO2) is both an important primary trace gaseous pollutant and a precursor to ozone and fine particulate matter production. There exist three widely used and publically available tropospheric NO2 Vertical Column Density (VCD) products based on OMI over East Asia, including QA4ECV from KNMI, OMNO2 from NASA and POMINO from Peking University. The spatiotemporal characteristics of tropospheric NO2 VCDs in each product have been extensively studied. However, quantitative knowledge of the differences between the three products is still inadequate.This research firstly updates the POMINO product developed by our group to version 2.1, including bug fixes and algorithm improvement, and expanding the spatial domain to East Asia, much of Southeast Asia and most of South Asia. Compared with QA4ECV and OMNO2 v4, POMINO v2.1 takes into account the anisotropy of surface reflectance and complex radiative effects of aerosols in the process of tropospheric NO2 AMF calculation. Then we quantitatively compare the NO2 data of QA4ECV, OMNO2 v4 and POMINO v2.1 in 2015—2020 based on either POMINO v2.1 or each product’s valid pixels.Results show that updates of POMINO do not significantly affect the retrieved NO2 VCDs (within 10% averaged over the spatial domain, dependent on seasons). When valid satellite pixels of three products are sampled consistently based on cloud radiation fraction of POMINO v2.1, the relative differences between the three products are about 10% averaged over Asia, although the maximum difference can reach 40% or more in severely polluted areas like Beijing-Tianjin-Hebei. A sensitivity test based on POMINO algorithm shows that tropospheric NO2 VCDs with implicit aerosol correction (as QA4ECV and OMNO2 v4) in December 2017 are lower than those with explicit correction by about 26.4% over Beijing-Tianjin-Hebei, and more than 11% over the whole North China Plain. As far as the long-term trend is concerned, all the three products show a nearly 30% decrease of annual mean tropospheric NO2 VCDs in Beijing-Tianjin-Hebei in 2015—2020, in contrast to relatively small VCD changes over the Yangtze River Delta. When valid satellite pixels are sampled based on each product’s own cloud screening, POMINO v2.1 provides much more valid pixels in polluted situations by 11%—44% and reduces the sampling bias, as a result of its explicit representation of aerosol optical effects in the NO2 and prerequisite cloud retrieval process.This research provides a basis for using and interpreting the three products, including their differences, effects of sampling and impacts of aerosol representation. Our results offer insight for better understanding of the pollution of nitrogen oxides and influences of current emission reductions.

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