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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  06 Apr 2020

06 Apr 2020

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A revised version of this preprint is currently under review for the journal ACP.

Discrepancies between MICS-Asia III Simulation and Observation for Surface Ozone in the Marine Atmosphere over the Northwestern Pacific Asian Rim Region

Hajime Akimoto1, Tatsuya Nagashima1, Li Jie2, Joshua S. Fu3,4, and Zifa Wang2 Hajime Akimoto et al.
  • 1National Institute for Environmental Studies, Onogawa, Tsukuba 305-8506, Japan
  • 2Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 3Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA
  • 4Climate Change Science Institute and Computational Sciences and Engineering Division, Oak Ridge national Laboratory, Oak Ridge, TN 37831, USA

Abstract. In order to identify the causes of overestimate of the surface-level O3 mixing ratio simulated by three regional chemical-transport models, namely NAQPMS v.3 (abbreviated as NAQM in this paper), CMAQ v.5.0.2, and CMAQ v.4.7.1, compared to the EANET observational data at a marine remote site at Oki in July 2010 in the context of MICS-Asia III, analyses of hourly data of O3 mixing ratios and net ozone production were made. In addition to Oki, model-simulated and observational data for two other EANET marine sites, Hedo and Ogasawara, were also examined. Three factors, i.e., long-range transport from the continent, in-situ photochemical formation, and dry deposition of O3 on seawater have been found to contribute to the overestimate by these regional models at Oki. The calculated O3 mixing ratios during long-range transport from the continent were much higher for all the three models than those of the observation. In-situ photochemical formation, demonstrated by a distinct diurnal variation which was not discerned in the observational data, was seen in the simulated data of all the three models and ascribed to the virtual transport of NOx from the southern urban areas of the main island of Japan. At Hedo and Ogasawara overestimate of O3 in oceanic air mass was found for CMAQ v.5.0.2 and v. 4.7.1, while good agreement was obtained by NAQM. The overestimate by CMAQ models were inferred to be due to the use of too small dry deposition rate of O3 compared to NAQM in the Northwestern Pacific. However, the dry deposition velocity of O3 in the Bohai Bay and the Yellow Sea has been assumed to be comparable to that of the open ocean in all the three models, which could have resulted in the overestimate of O3 mixing ratios in this area and also in the long-range transport of O3 from the continent to Oki. A higher value of dry deposition velocity in this marine area is expected considering the higher content of organics in the surface sea layer brought by rivers and atmospheric wet deposition. Empirical measurements of the dry deposition flux in this area is highly recommended, since it would affect the simulated mixing ratios in the down-wind region and the estimate of transboundary transport of ozone from the continent to the Pacific rim region.

Hajime Akimoto et al.

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Hajime Akimoto et al.

Hajime Akimoto et al.


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