[A-AS21] 大気化学

[AAS21-P24] CONTRAIL-CMEで観測された対流圏CO2の平均的時空間変動

*梅澤 拓¹、町田 敏暢¹、澤 庸介²、松枝 秀和²、丹羽 洋介² (1.国立環境研究所、2.気象研究所地球化学研究部)

CONTRAIL is the ongoing project that measures atmospheric trace gases during intercontinental flights of Japan Airlines. Atmospheric CO₂ concentration is analyzed using Continuous CO₂ Measuring Equipment (CME) onboard the aircraft. From ~20 thousands of measurement flights since 2005, extensive number of CO₂ data (~2 millions) along level-flight and ascent/descent tracks have been obtained, enabling us to well characterize spatiotemporal distributions of atmospheric CO₂ covering large part of the globe especially the Asia-Pacific regions. In this study, we define ∆CO₂ as a deviation from the long-term trend observed at a northern hemispheric baseline station Mauna Loa, Hawaii, to illustrate climatological CO₂ distributions including seasonal and shorter-term variations. For instance, over airports in Japan, ∆CO₂ reaches seasonal maximum at the end of April with higher values near the surface. In this season, high ∆CO₂ spreads east of the Asian continent in the upper troposphere over the northern Pacific. In contrast, seasonal minimum of ∆CO₂ occurs in September with more depletion in the upper troposphere. The summertime low ∆CO₂ in the upper troposphere appears to be more pronounced over the Asian continent than over the Pacific. Likewise, we present seasonal variations of vertical profiles of tropospheric ∆CO₂ over various airports and of spatial distributions in the upper troposphere in large-scale perspective, and discuss them from viewpoints of seasonally varying continental sources/sinks and atmospheric transport.