5:15 PM - 7:15 PM
[AAS11-P25] Measurements of CO2 column mixing ratio around the Osaka Itami Airport
Keywords:greenhouse gas, urban, Osaka, airport, carbon dioxide, CO2
Introduction
Predicting the atmospheric concentration of CO2, a greenhouse gas, remains uncertain, and the precise sources and sinks of CO2 emissions are still unexplained. In particular, there is a critical lack of detailed data on urban areas, where significant emissions are expected, especially in terms of upper atmospheric observations. Therefore, this study reports on the slant column mean mixing ratio of CO2 during the daytime around Osaka International Airport (Osaka Itami Airport: ITM), measuring their temporal and seasonal variations. By analyzing these data, we explore the influence of aircraft emissions, living environments, topography, and meteorological factors on greenhouse gas emissions.
Methods
Observations were conducted at four locations around ITM. The airport's runway extends from southeast to northwest. These four locations include two sites approximately 1 km away from the runway but not aligned with it, one southeast site located approximately 0.5 km from the runway's southeastern end (landing direction), and one northwest site located approximately 0.5 km from the runway's northwestern end (takeoff direction). A portable CO2 measurement device was used, which operates by analyzing the absorption of infrared light from sunlight to determine atmospheric CO2 concentrations. This method allows for CO2 measurements not only at ground level but also at higher altitudes where aircraft pass through.
The observations were carried out during four weekends across autumn, winter, and spring, with data collected for over six hours during the daytime. Along with the CO2 seasonal variations at the four sites, meteorological data were recorded. Additionally, similar observations were conducted on weekdays at Kwansai Gakuin Senri International Campus (SOIS) in Minoh City, Osaka Prefecture, for comparative analysis.
Results
Figure 1, column mixing ratios (arbitrary units) of CO2 around ITM and in SOIS, presents the observation data from September 4–30, 2024, representing autumn. The mean values are shown when the solar altitude is between 51.9° and 52.6°, the error bars represent the standard deviation of the fluctuating values. The white squares are the observed data around ITM and the red circles are those of SOIS. SW, SE, NW and NE accompanying the white squares indicate the direction of the observation point as seen from the ITM runway: south-west, south-east, north-west and north-east respectively.
The CO2 column-averaged mixing ratios observed at ITM were generally lower than those observed at SOIS, except for the NW site. Considering that aircraft take off in the NW direction, it is plausible that the higher CO2 levels at the NW site were influenced by aircraft emissions. Alternatively, it is possible that the increase in CO2 levels observed around September 23 at both ITM and SOIS was caused by another unidentified factor unrelated to aircraft emissions.
In contrast, no such prominent trends in CO2 concentrations were observed during the winter observation period in December 2024. Column-averaged mixing ratios of CO2 were even slightly higher at SOIS compared to ITM, and differences in CO2 levels among the observation sites around ITM were minimal. Furthermore, overall CO2 levels were higher during the winter observation period.
Discussion
This difference may be attributed to reduced photosynthetic activity during winter. Compared to SOIS, ITM's surrounding area has relatively more preserved natural environments. On the other hand, SOIS is situated in a densely developed residential area, and the presence of nearby mountains may also play a role in influencing observations.
In autumn, when photosynthesis was relatively active around ITM, CO2 absorption lowered the overall CO2 levels, making the impact of aircraft emissions more noticeable. However, during winter, reduced CO2 absorption due to weaker photosynthesis may have led to an overall increase in CO2 levels, obscuring the effects of aircraft emissions. In contrast, the minimal photosynthetic CO2 absorption around SOIS likely resulted in little to no noticeable seasonal effects.
Future Outlook
Spring observations are scheduled for March–April 2025, but they cannot be reported in this paper. It is anticipated that changes similar to those observed in autumn may occur during this period of heightened photosynthetic activity. Comparing data between ITM and SOIS can reduce uncertainties, but more frequent and long-term observations are expected to further minimize variability due to day-to-day fluctuations. Increasing the number of observations will enhance the reliability of the findings in future efforts.
Predicting the atmospheric concentration of CO2, a greenhouse gas, remains uncertain, and the precise sources and sinks of CO2 emissions are still unexplained. In particular, there is a critical lack of detailed data on urban areas, where significant emissions are expected, especially in terms of upper atmospheric observations. Therefore, this study reports on the slant column mean mixing ratio of CO2 during the daytime around Osaka International Airport (Osaka Itami Airport: ITM), measuring their temporal and seasonal variations. By analyzing these data, we explore the influence of aircraft emissions, living environments, topography, and meteorological factors on greenhouse gas emissions.
Methods
Observations were conducted at four locations around ITM. The airport's runway extends from southeast to northwest. These four locations include two sites approximately 1 km away from the runway but not aligned with it, one southeast site located approximately 0.5 km from the runway's southeastern end (landing direction), and one northwest site located approximately 0.5 km from the runway's northwestern end (takeoff direction). A portable CO2 measurement device was used, which operates by analyzing the absorption of infrared light from sunlight to determine atmospheric CO2 concentrations. This method allows for CO2 measurements not only at ground level but also at higher altitudes where aircraft pass through.
The observations were carried out during four weekends across autumn, winter, and spring, with data collected for over six hours during the daytime. Along with the CO2 seasonal variations at the four sites, meteorological data were recorded. Additionally, similar observations were conducted on weekdays at Kwansai Gakuin Senri International Campus (SOIS) in Minoh City, Osaka Prefecture, for comparative analysis.
Results
Figure 1, column mixing ratios (arbitrary units) of CO2 around ITM and in SOIS, presents the observation data from September 4–30, 2024, representing autumn. The mean values are shown when the solar altitude is between 51.9° and 52.6°, the error bars represent the standard deviation of the fluctuating values. The white squares are the observed data around ITM and the red circles are those of SOIS. SW, SE, NW and NE accompanying the white squares indicate the direction of the observation point as seen from the ITM runway: south-west, south-east, north-west and north-east respectively.
The CO2 column-averaged mixing ratios observed at ITM were generally lower than those observed at SOIS, except for the NW site. Considering that aircraft take off in the NW direction, it is plausible that the higher CO2 levels at the NW site were influenced by aircraft emissions. Alternatively, it is possible that the increase in CO2 levels observed around September 23 at both ITM and SOIS was caused by another unidentified factor unrelated to aircraft emissions.
In contrast, no such prominent trends in CO2 concentrations were observed during the winter observation period in December 2024. Column-averaged mixing ratios of CO2 were even slightly higher at SOIS compared to ITM, and differences in CO2 levels among the observation sites around ITM were minimal. Furthermore, overall CO2 levels were higher during the winter observation period.
Discussion
This difference may be attributed to reduced photosynthetic activity during winter. Compared to SOIS, ITM's surrounding area has relatively more preserved natural environments. On the other hand, SOIS is situated in a densely developed residential area, and the presence of nearby mountains may also play a role in influencing observations.
In autumn, when photosynthesis was relatively active around ITM, CO2 absorption lowered the overall CO2 levels, making the impact of aircraft emissions more noticeable. However, during winter, reduced CO2 absorption due to weaker photosynthesis may have led to an overall increase in CO2 levels, obscuring the effects of aircraft emissions. In contrast, the minimal photosynthetic CO2 absorption around SOIS likely resulted in little to no noticeable seasonal effects.
Future Outlook
Spring observations are scheduled for March–April 2025, but they cannot be reported in this paper. It is anticipated that changes similar to those observed in autumn may occur during this period of heightened photosynthetic activity. Comparing data between ITM and SOIS can reduce uncertainties, but more frequent and long-term observations are expected to further minimize variability due to day-to-day fluctuations. Increasing the number of observations will enhance the reliability of the findings in future efforts.