Ozone (O3), an isomer of oxygen (O2), is a trace gas with an irritating odor and is extremely oxidizing (Li, 2016) and is mainly distributed in the stratosphere and troposphere of the atmosphere(Guo, Shi, & Xing, 2018). The depletion of the stratospheric ozone layer has been one of the most important environmental issues in the last 40 years, with the breakdown of human emitted compounds such as chlorofluorocarbons (CFCs) in the stratosphere releasing chlorine atoms capable of destroying ozone catalytically (Molina & Rowland, 1974; Stolarski & Cicerone, 1974), chlorine and bromine caused ozone depletion in the stratosphere to persist until the 1990s, after which ozone depletion subsides and there is a slow recovery of stratospheric ozone(Chipperfield et al., 2017). There has been scientific and public interest in the spatial and temporal variability of tropospheric ozone (Nagashima, Sudo, Akimoto, Kurokawa, & Ohara, 2017), and tropospheric ozone can irritate the respiratory system and the eyes (Silva et al., 2013) and have a detrimental effect on vegetation physiology, leading to reduced crop yields (Hollaway, Arnold, Challinor, & Emberson, 2012).
The observation means of ozone mainly include satellite remote sensing and ground-based observation. Ground-based monitoring has high precision and can simultaneously obtain various atmospheric environmental parameters, but ground monitoring of stations is sparsely distributed and expensive (Khan, Kumar, & Zhao, 2019; Liu, Lin, Qin, He, & Li, 2019). Satellite remote sensing observations precisely compensate for the shortcomings with high spatial coverage and temporal continuity, which can be used to observe ozone numerical changes over a large spatial range at the same time to comprehensively reflect atmospheric pollution characteristics (Xiao et al., 2016).
The increase in surface ozone has occurred primarily in Asia (Ziemke et al., 2019), most of the anthropogenic emissions of ozone-producing reactive gases have shifted from North America and Europe to Asia (Chang, Petropavlovskikh, Copper, Schultz, & Tao, 2017), and tropospheric ozone indicates an increase that is global but still strongly regional (Oltmans et al., 2013). As a result of further changes in emissions of ozone precursors and climate change, the hourly ozone distribution will continue to change at different locations around the globe (Lefohn et al., 2018). Japanese ozone has been investigated by numerous researchers; Japanese ozone data showed a significant upward trend in ozone from 1966 through the middle of the 1990s, after which the increasing trend moderated(Oltmans et al., 2013); Ozone levels in Japan showed an increasing trend up to the year 2005, and after 2005 the rise slowed or even showed a declining trend(Parrish et al., 2012); The relationship between the trends in air pollution across Japan and Tokyo from 1970 to 2012, elucidating that concentrations of air pollutants were steadily declining due to a variety of source measures(Wakamatsu, Morikawa, & Ito, 2013); These results are in contrast to the findings of him, who analyzed ozone changes in Japan from 1998 to 2007 and found that, except for an increasing trend of ozone at individual mountain sites, the annual average trend of ozone change at plain sites was not obvious(Tanimoto, Ohara, & Uno, 2009); The increase of surface ozone concentration in Japan between 1990 and 2010 was due to the non-titration effect and the increase of cross-border migration(Kimoto, 2015). The work presented in this paper builds on this foundation by providing an in-depth analysis of the spatiotemporal variation of ozone in Japan from 2010 to 2021, and discusses its future trends, potential source areas, and influencing factors in an attempt to provide a theoretical basis for the solution of Japan's ozone pollution problem, and the investigation of the ozone problem in Japan is of great importance to the world.
Overview Of The Study Area
It is located in the eastern part of the Asian and European continents and in the northwestern part of the Pacific Ocean. The region is bordered by China, North Korea, and South Korea, roughly between 24°N-45°N and 123°E-149°E, with a land area of approximately 378,000 km2. With a total population of around 126 million, Japan has 47 first-class administrative regions, which are divided into eight main regions: Hokkaido region, Tohoku region, Kanto region, Chubu region, Kinki region, Chugoku region, Shikoku region and Kyushu region (Fig. 1). The climate of the country is monsoon temperate and subtropical, with many rainy months in June and typhoons in the summer and fall, in addition to significant temperature differences between north and south. About 75% of Japan's land is mountainous and hilly, with small-scale mountain basins and plains scattered throughout the country, and 67% of the country is covered by forests.
Japan entered a period of post-war economic recovery and rapid economic development in the 1950s, which resulted in incidents of air pollution and a public rights movement and prompted the formation of laws and environmental regulations in Japan. During the 1970s, there was a severe photochemical smog incident in Tokyo in which the major component was ozone, which led to poisoning of some students and subsequent coma. Photochemical smog alerts continue to occur after more than 30 years of treatment. Studies have shown that ozone pollution is controlled by the emissions of ozone precursors and their complex interconversion relations, leading to an extremely complex and recurring ozone pollution problem that has become a global environmental challenge(Yang, Huang, Shi, Fan, & Zhou, 2018).
Analysis Of Monitoring Data
Data source and processing
Daily data on ozone (O3) and nitrogen dioxide (NO2) for the years 2010 to 2021 used in this study were obtained from the Ozone Monitoring Instrument (OMI) aboard the Aura spacecraft, which was successfully launched by NASA in July 2004 with a spatial resolution of 13 km×24 km – the first of its kind, the sensor has a field of view of 114, a wavelength range of 270 to 500 nm, an average spectral resolution of 0.5 nm, and a scan width of 2600 km. In this paper, the extracted latitude, longitude, concentration, and cloud data are firstly processed by a series of raster calculation, kriging interpolation, averaging, and masking using Python software, and finally the spatial and temporal distribution of ozone column concentration in Japan is mapped by ArcGIS 10.6(S. Xie, Ju, & Zhang, 2017).
The data for five natural factors, namely precipitable water (SVP), air temperature (TEM), barometric pressure (PS), lift index (LI) and relative humidity (RH), were taken from the NOAA Weather Monitoring Network software program of the NCEP-NCAR Global Atmospheric Reanalysis dataset. The population density dataset was obtained from the LandScan data website developed by the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL), as well as gross domestic product (GDP) data were obtained from an article published by Jiandong Chen (2022) and other academics in the journal Scientific Data (2022) and others in the journal Scientific Data, a corrected real GDP data based on nighttime light data.
The Digital Elevation Model (DEM) data were obtained from the Shuttle Radar Topography Mission (SRTM) of the U.S. Space Shuttle Endeavour, which acquired radar image data ranging from 60°N to 56°S, covering more than 80% of the Earth's land surface. The spatial resolution of the DEM data used in this paper is 1 km, and cropping and masking of the data is carried out in ArcGIS 10.6.
The backward trajectory model is based on reanalysis of data from (Global Data Assimilation System (GDAS) 2010–2021 provided by the National Centers for Environmental Prediction (NEPC), using a hybrid Lagrangian and Eulerian diffusion model. Here we simulate the 24-hour day back trajectory, choosing the 500 m height where the wind field is most stable, and use Angle Distance to group airflow based on the horizontal direction of transport of the study region(Chen et al., 2022).