the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Mar 2024
Observations of the vertical distributions of summertime atmospheric pollutants in Nam Co: OH production and source analysis
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.
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RC1: 'Comment on egusphere-2024-461', Anonymous Referee #1, 22 Mar 2024
Xing et al. learned the vertical variations and sources of O3 and HONO and their precursors on the Tibetan Plateau. The authors found that 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. From the point of view of the data and scientific value, I recommend this manuscript being published in ACP after following revisions.
- Authors should reorganize the abstract. The significance of the research and the most significant scientific findings should be fully presented.
2.The description of the retrieval algorithm and the corresponding uncertainty analysis of vertical profiles is missing. The authors could even put them in the supplementary materials.
3.Section 2.1 emphasized HCHO, which seems to be irrelevant to this study. I suggest the authors to modificate Figure S1 to narrow the area and focus on the area around Nam Co.
4.The authors concluded “high concentration NO2 should be attributed to the transport process from the NOx produced by ice and snow on the top of Mt. Tanggula”. Can you give adequate data and literature support?
- P6 L194-197, “Moreover, the large-scaled spatial distributions of AOD, O3, NO2 and HCHO over CAS (NAMORS) were monitored by Himawari-8 (Bessho et al., 2016), OMI (Veefkind et al., 2004) and TROPOMI (Griffin et al., 2018; Su et al., 2020), respectively.”
- P6L202, increases > increased
- P7L212-213, shown > was, and > but
- P12L390, first > firstly
Citation: https://doi.org/10.5194/egusphere-2024-461-RC1 - RC2: 'Comment on egusphere-2024-461', Anonymous Referee #2, 14 Apr 2024
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