Retrieval of O3, NO2, BrO and OClO Columns from Ground-Based Zenith Scattered Light DOAS Measurements in Summer and Autumn over the Northern Tibetan Plateau

Remote Sensing

Sebastian Donner¹  Myojeong Gu¹  Thomas Wagner¹  Steffen Dörner¹  Xing Li²  Zhiyong Liang²  Jinguang Lv³  Jianzhong Ma⁴  Siyang Cheng⁴  Xiangdong Zheng⁴  Wenqian Zhang⁴  Jun Du⁵ 

[1] Max Planck Institute for Chemistry, D-55020 Mainz, Germany;Meteorological Bureau of Golmud, Golmud 816000, China;State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;State Key Laboratory of Severe Weather & CMA Key Laboratory of Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, Beijing 100081, China;Tibet Institute of Plateau Atmospheric and Environmental Sciences, Lhasa 850000, China;

关键词: stratospheric trace gases;    ground-based remote sensing;    zenith DOAS;    Tibetan Plateau;   

DOI  :  10.3390/rs13214242

来源: DOAJ

【 摘 要 】

Ground-based zenith scattered light differential optical absorption spectroscopy (DOAS) measurements were performed in summer and autumn (27 May–30 November) 2020 at Golmud (94°54′ E, 36°25′ N; 2807.6 m altitude) to investigate the abundances and temporal variations of ozone (O₃) and its depleting substances over the northern Tibetan Plateau (TP). The differential slant column densities (dSCDs) of O₃, nitrogen dioxide (NO₂), bromine monoxide (BrO), and chlorine dioxide (OClO) were simultaneously retrieved from scattered solar spectra in the zenith direction during the twilight period. The O₃ vertical column densities (VCDs) were derived by applying the Langley plot method, for which we investigated the sensitivities to the chosen wavelength, the a-priori O₃ profile and the aerosol extinction profile used in O₃ air mass factor (AMF) simulation as well as the selected solar zenith angle (SZA) range. The mean O₃ VCDs from June to November 2020 are 7.21 × 10¹⁸ molec·cm⁻² and 7.18 × 10¹⁸ molec·cm⁻² at sunrise and sunset, respectively. The derived monthly variations of the O₃ VCDs, ranging from a minimum of 6.9 × 10¹⁸ molec·cm⁻² in October to 7.5 × 10¹⁸ molec·cm⁻² in November, well matched the OMI satellite product, with a correlation coefficient R = 0.98. The NO₂ VCDs at SZA = 90°, calculated by a modified Langley plot method, were systematically larger at sunset than at sunrise as expected with a pm/am ratio of ~1.56. The maximum of the monthly NO₂ VCDs, averaged between sunrise and sunset, was 3.40 × 10¹⁵ molec·cm⁻² in July. The overall trends of the NO₂ VCDs were gradually decreasing with the time and similarly observed by the ground-based zenith DOAS and OMI. The average level of the BrO dSCD_90°–80° (i.e., dSCD between 90° and 80° SZA) was 2.06 × 10¹⁴ molec·cm⁻² during the period of June–November 2020. The monthly BrO dSCD_90°–80° presented peaks in August and July for sunrise and sunset, respectively, and slowly increased after October. During the whole campaign period, the OClO abundance was lower than the detection limit of the instrument. This was to be expected because during that season the stratospheric temperatures were above the formation temperature of polar stratospheric clouds. Nevertheless, this finding is still of importance, because it indicates that the OClO analysis works well and is ready to be used during periods when enhanced OClO abundances can be expected. As a whole, ground-based zenith DOAS observations can serve as an effective way to measure the columns of O₃ and its depleting substances over the TP. The aforementioned results are helpful in investigating stratospheric O₃ chemistry over the third pole of the world.

【 授权许可】

Unknown