@article{oai:kitami-it.repo.nii.ac.jp:02000328,
 author = {Yugo Kanaya and Kazuyuki Miyazaki and Fumikazu Taketani and Takuma Miyakawa and Hisahiro Takashima and Yuichi Komazaki and Xiaole Pan and Saki Kato and Kengo Sudo and Takashi Sekiya and Jun Inoue and Kazutoshi Sato and Kazuhiro Oshima},
 journal = {Atmospheric Chemistry and Physics},
 month = {},
 note = {Abstract. Constraints from ozone (O3) observations over
oceans are needed in addition to those from terrestrial regions
to fully understand global tropospheric chemistry and
its impact on the climate. Here, we provide a large data set of
ozone and carbon monoxide (CO) levels observed (for 11 666
and 10 681 h, respectively) over oceans. The data set is derived
from observations made during 24 research cruise legs
of R/V Mirai during 2012 to 2017, in the Southern, Indian,
Pacific, and Arctic oceans, covering the region from 67 S
to 75 N. The data are suitable for critical evaluation of the
over-ocean distribution of ozone derived from global atmospheric
chemistry models. We first give an overview of the
statistics in the data set and highlight key features in terms
of geographical distribution and air mass type. We then use
the data set to evaluate ozone mixing ratio fields from the
tropospheric chemistry reanalysis version 2 (TCR-2), produced
by assimilating a suite of satellite observations of
multiple species into a global atmospheric chemistry model,
namely CHASER. For long-range transport of polluted air
masses from continents to the oceans, during which the effects
of forest fires and fossil fuel combustion were recognized,
TCR-2 gave an excellent performance in reproducing
the observed temporal variations and photochemical buildup
of O3 when assessed from 1O3=1CO ratios. For clean marine
conditions with low and stable CO mixing ratios, two
focused analyses were performed. The first was in the Arctic
(> 70 N) in September every year from 2013 to 2016;
TCR-2 underpredicted O3 levels by 6.7 ppbv (21 %) on average.
The observed vertical profiles from O3 soundings from
R/V Mirai during September 2014 had less steep vertical
gradients at low altitudes (> 850 hPa) than those obtained
by TCR-2. This suggests the possibility of a more efficient
descent of the O3-rich air from above than assumed in the
models. For TCR-2 (CHASER), dry deposition on the Arctic
ocean surface might also have been overestimated. In the
second analysis, over the western Pacific equatorial region
(125–165 E, 10 S to 25 N), the observed O3 level more
frequently decreased to less than 10 ppbv in comparison to
that obtained with TCR-2 and also those obtained in most
of the Atmospheric Chemistry Climate Model Intercompari-
son Project (ACCMIP) model runs for the decade from 2000.
These results imply loss processes that are unaccounted for
in the models. We found that the model’s positive bias positively
correlated with the daytime residence times of air
masses over a particular grid, namely 165–180 E and 15–
30 N; an additional loss rate of 0.25 ppbv h􀀀1 in the grid best
explained the gap. Halogen chemistry, which is commonly
omitted from currently used models, might be active in this
region and could have contributed to additional losses. Our
open data set covering wide ocean regions is complementary
to the Tropospheric Ozone Assessment Report data set,
which basically comprises ground-based observations and
enables a fully global study of the behavior of O3.},
 pages = {7233--7254},
 title = {Ozone and carbon monoxide observations over open oceans on R/V Mirai from 67 S to 75 N during 2012 to 2017: testing global chemical reanalysis in terms of Arctic processes, low ozone levels at low latitudes, and pollution transport},
 volume = {19},
 year = {2019}
}