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全文摘要次数: 201 全文下载次数: 387
引用本文:

DOI:

10.11834/jrs.20210302

收稿日期:

2020-07-23

修改日期:

2020-12-25

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基于高分五号大气痕量差分吸收光谱仪的甲醛反演(高分大气)
摘要:

大气痕量差分吸收光谱仪(EMI, Environmental trace gases Monitoring Instrument)是搭载在“高分5号”(GF5)卫星上的覆盖紫外-可见光波段的光谱仪,用于测量240~710 nm波长范围内的地球后向散射和太阳辐射,旨在量化全球对流层和平流层微量气体的分布,如臭氧,二氧化氮等。本文关注EMI载荷对大气弱痕量气体甲醛(HCHO)的探测能力。本文通过模拟分析讨论EMI进行HCHO反演的需求和可行性。研究结果表明EMI的辐照度波长校准精度高,但在不同行之间存在较大的不均匀性,其波长校正的精度与仪器的狭缝函数(FWHM)高度依赖行位置的变化,其中UV2波段的FWHM的变化范围为0.34-0.55 nm,对应的均值和方差为0.414±0.047 nm。基于EMI的HCHO反演的结果表明,EMI UV2频段的标称信噪比较低,使得利用差分光吸收光谱法(DOAS)得的HCHO斜柱浓度(SCD)存在较大的随机误差和拟合残差。现阶段我们评估得到的EMI HCHO的SCD不确定性为1.2×1016 molec/cm2。与国际同类载荷(TROPOMI、OMI)的交叉对比验证结果表明,EMI可以捕捉到中国地区夏季HCHO的空间分布特征。EMI TROPOMI与EMI OMI的相关系数大于0.8。但是在华东地区EMI HCHO普遍高于OMI和TROPOMI,这可能与不完善的波长校准以及不完美的云筛除方案有关。本文的研究证明了EMI对夏季HCHO的探测潜力及不足,可为后续类似载荷的指标设计和算法研发提供参考。

Formaldehyde retrieval based on Environmental Trace Gases Monitoring Instrument (EMI) onboard GaoFen 5 satellite
Abstract:

Onboard the Chinese GaoFen-5(GF5) satellite, Environmental trace gases Monitoring Instrument (EMI) is a nadir-viewing wide-field spectrometer measuring solar back-scattered earthshine radiances in the ultraviolet and visble spectra range, which aims to quantify the global distribution of tropospheric and stratospheric trace gases, and had launched on 9 May 2018. In this paper, we evaluated the requirements and feasibility for HCHO retrieval based on simulation. We find that the irradiance of EMI is well calibrated with smaller wavelength shift, however, the FWHM and wavelength shifts are highly dependent on the cross-track position than OMI and TROPOMI. The results of simulation demonstrated that HCHO retrieval is prone to noise and the nominal SNR of EMI UV2 band is lower and will lead larger random error in HCHO SCD retrieval as well as the fit residual by using the differential optical absorption spectrometry (DOAS) method. We explore the SCD uncertainty of EMI HCHO is 1.2×1016 molec/cm2.We present here the first results of formaldehyde retrieval, we find that EMI can captures the spatial distribution of HCHO. The intercomparision of EMI TROPOMI and EMI OMI show consistent in spatial, with the correlation coefficient larger than 0.8. However, EMI HCHO are generally higher than that of OMI and TROPOMI over east China, which may be result from the imperfect wavelength calibration and the contamination of remaining cloud after cloud screening. The study in this paper demonstrated the potential of EMI for HCHO retrieval in summer.

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