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Sensors 2018, 18(7), 2209; https://doi.org/10.3390/s18072209

Assessment of Retrieved N2O, NO2, and HF Profiles from the Atmospheric Infrared Ultraspectral Sounder Based on Simulated Spectra

1
State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
2
University of Chinese Academy of Science, Beijing 100049, China
3
Remote Sensing Technology Institute, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Weßling, Germany
4
National Satellite Meteorological Center, China Meteorological Administration, Beijing 100081, China
5
China Center for Resources Satellite Data and Application, Beijing 100094, China
*
Author to whom correspondence should be addressed.
Received: 25 May 2018 / Revised: 27 June 2018 / Accepted: 6 July 2018 / Published: 9 July 2018
(This article belongs to the Section Remote Sensors)
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Abstract

The Atmospheric Infrared Ultraspectral Sounder (AIUS), the first high-resolution (0.02 cm−1) solar occultation sounder, aboard GF5, was launched in May 2018 from China. However, relevant studies about vertical profiles of atmospheric constituents based on its operational data were not conducted until half a year later. Due to an urgent need for Hin-orbit tests, the real spectra (called reference spectra hereafter) were substituted with simulated spectra calculated from the reference forward model (RFM) plus different random noises at different altitudes. In the generation process of the reference spectra for N2O, NO2, and HF species, ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer instrument on the SCISAT satellite) level 2 products replace corresponding profiles included in the atmospheric background profiles. The optimal estimation method is employed to extract N2O, NO2, and HF profiles in this study. Comparing the retrieved results with ACE-FTS level 2 products, the relative deviations for these three species are calculated. For N2O, the average relative deviation is less than 6% at altitudes below 25 km, while larger deviations are observed in the range of 25–45 km, with the maximum being at ~25%. Additionally, the difference for NO2 is less than 5% in the 20–45 km range, with a larger discrepancy found below 20 km and above 45 km; the maximum deviation reaches ±40%. For HF, the relative deviation is less than 6% for all tangent heights, implying satisfactory retrieval. The vertical resolution, averaging kernel, and number of degrees of freedom are used to assess the retrieval algorithm, which indicate that the retrieved information content is much more attributable to the reference spectra contribution than to the a priori profile. Finally, a large number of retrieval tests are performed for N2O, NO2, and HF in selected areas covering the Arctic region, northern middle latitude, tropics, southern middle latitude, and Antarctic region, and reliable results are obtained. Thus, to a great extent, the algorithm adopted in the AIUS system can process retrievals reliably and precisely. View Full-Text
Keywords: GF5 AIUS; occultation; retrieval algorithm; microwindow selection; N2O; NO2; HF GF5 AIUS; occultation; retrieval algorithm; microwindow selection; N2O; NO2; HF
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Wang, H.; Li, X.; Xu, J.; Zhang, X.; Ge, S.; Chen, L.; Wang, Y.; Zhu, S.; Miao, J.; Si, Y. Assessment of Retrieved N2O, NO2, and HF Profiles from the Atmospheric Infrared Ultraspectral Sounder Based on Simulated Spectra. Sensors 2018, 18, 2209.

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