Preprints
https://doi.org/10.5194/egusphere-2024-461
https://doi.org/10.5194/egusphere-2024-461
15 Mar 2024
 | 15 Mar 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Observations of the vertical distributions of summertime atmospheric pollutants in Nam Co: OH production and source analysis

Chengzhi Xing, Cheng Liu, Chunxiang Ye, Xiangguang Ji, Jingkai Xue, Jinping Ou, Hongyu Wu, and Qihou Hu

Abstract. The Tibetan Plateau (TP) plays a key role in regional environment and global climate change, however, the lack of vertical observation hinders a deeper understanding of the atmospheric chemistry and atmospheric oxidation capacity (AOC) on the TP. In this study, we conducted MAX-DOAS measurements at Nam Co, central TP, to observe the vertical profiles of aerosol, water vapor, NO2, HONO and O3 from May to July 2019. In addition to NO2 mainly exhibiting a Gaussian shape with the maximum value appearing at 300–400 m, other four species all showed an exponential shape and decreased with the increase of height. The maximum values of monthly averaged aerosol (0.17 km-1) and O3 (66.71 ppb) occurred on May, water vapor (3.68×1017 molec cm-3) and HONO (0.13 ppb) appeared on July, while NO2 (0.39 ppb) occurred on June at 200–400 m layer. Water vapor, HONO and O3 all exhibited a multi-peak pattern, and aerosol appeared a bi-peak pattern for their averaged diurnal variation. Moreover, we found O3 and HONO were the main contributors to OH on the TP. The averaged vertical profiles of OH production rates from O3 and HONO all exhibited an exponential shape, and decreased with the increase of height with the maximum values of 2.61 ppb/h and 0.49 ppb/h at the bottom layer, respectively. In addition, source analysis for HONO and O3 were conducted based on vertical observations. The heterogeneous reaction of NO2 on wet surfaces was a significant source of HONO, which obviously associated with water vapor concentration and aerosol extinction. The maximum values of HONO/NO2 appeared around water vapor being 1.0×1017 molec cm-3 and aerosol being lager 0.15 km-1 under 1.0 km, and the maximum values usually accompanied with water vapor being 1.0–2.0×1017 molec cm-3 and aerosol being lager 0.02 km-1 at 1.0–2.0 km. O3 was potentially sourced from south Asian subcontinent and Himalayas through long-range transport. Our results enrich the new understanding of vertical distribution of atmospheric components and explained the strong AOC on the TP.

Chengzhi Xing, Cheng Liu, Chunxiang Ye, Xiangguang Ji, Jingkai Xue, Jinping Ou, Hongyu Wu, and Qihou Hu

Status: open (until 26 Apr 2024)

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  • RC1: 'Comment on egusphere-2024-461', Anonymous Referee #1, 22 Mar 2024 reply
Chengzhi Xing, Cheng Liu, Chunxiang Ye, Xiangguang Ji, Jingkai Xue, Jinping Ou, Hongyu Wu, and Qihou Hu
Chengzhi Xing, Cheng Liu, Chunxiang Ye, Xiangguang Ji, Jingkai Xue, Jinping Ou, Hongyu Wu, and Qihou Hu

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Short summary
We learned the contributions of O3 and HONO to the production rates of OH in vertical space on the TP. A new insight was offered: the contributions of HONO and O3 to the production rates of OH on the TP are even greater than at lower-altitudes areas. This study will enrich the new understanding of vertical distribution of atmospheric components and explained the strong AOC on the TP.