Seasonal evaluation of tropospheric CO<sub>2</sub> over the Asia-Pacific region observed by the CONTRAIL commercial airliner measurements

Abstract

Abstract. Measurement of atmospheric carbon dioxide (CO2) is indispensable for top-down estimation of surface CO2 sources/sinks by an atmospheric transport model. Despite the growing importance of Asia in the global carbon budget, the region has only been sparsely monitored for atmospheric CO2 and our understanding of atmospheric CO2 variations in the region (and thereby that of the regional carbon budget) is still limited. In this study, we present climatological CO2 distributions over the Asia-Pacific region obtained from the CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) measurements. The high-frequency in-flight CO2 measurements over 10 years reveal a clear seasonal variation in CO2 in the upper troposphere (UT), with a maximum occurring in April–May and a minimum in August–September. The CO2 mole fraction in the UT north of 40∘ N is low and highly variable in June–August due to the arrival of air parcels with seasonally low CO2 caused by the summertime biospheric uptake in boreal Eurasia. For August–September in particular, the UT CO2 is noticeably low within the Asian summer monsoon anticyclone associated with the convective transport of strong biospheric CO2 uptake signal over South Asia. During September as the anticyclone decays, a spreading of this low-CO2 area in the UT is observed in the vertical profiles of CO2 over the Pacific Rim of continental East Asia. Simulation results identify the influence of anthropogenic and biospheric CO2 fluxes in the seasonal evolution of the spatial CO2 distribution over the Asia-Pacific region. It is inferred that a substantial contribution to the UT CO2 over the northwestern Pacific comes from continental East Asian emissions in spring; but in the summer monsoon season, the prominent air mass origin switches to South Asia and/or Southeast Asia with a distinct imprint of the biospheric CO2 uptake. The CONTRAIL CO2 data provide useful constraints to model estimates of surface fluxes and to the evaluation of the satellite observations, in particular for the Asia-Pacific region.

In situ observations of greenhouse gases over Europe during the CoMet 1.0 campaign aboard the HALO aircraft

“…While the observed gradient is similar to previously reported studies (e.g. Wofsy, 2011;Sweeney et al, 2015;Umezawa et al, 2018), measurements from CoMet 1.0 also clearly indicate the increase in atmospheric concentrations over the past years. For example, the CH 4 mixing ratios measured during the IMECC campaign in autumn 2009 (Geibel et al, 2012) were approximately 60 ppb lower throughout the atmospheric column than those observed in 2018.…”

Enhanced regional terrestrial carbon uptake over Korea revealed by atmospheric CO2 measurements from 1999 to 2017

“…However, unlike the clean‐air environment in Alaska where previous studies have been performed (Commane et al, 2017; Jeong et al, 2018), Korea is located at the center of the East Asia region where a rapid increase in anthropogenic carbon emissions have been reported over the recent decades (Global Carbon Project, 2018). The higher increasing trends of and than that of the globally averaged CO 2 concentration (2.07 ppm/year), derived from the NOAA/ESRL data ( Dlugokencky & Tans, 2019), indicate that the influences of anthropogenic emissions on the spatiotemporal variations in CO 2 concentrations cannot be negligible over the region as highlighted in previous modelling (Ballav et al, 2012, 2016) and observation studies (Umezawa et al, 2018).…”

Interannual Variation of Upper Tropospheric CO over the Western Pacific Linked with Indonesian Fires

“…The seasonal cycle patterns in the NH often show a maximum in spring and a minimum in summer, but CO increases around October-November were considerably smaller in the NH than the SH. It is suggested that the seasonal CO signals due to Indonesian fire emissions were significantly masked by continental outflows of larger anthropogenic emissions from the East Asia region to the western North Pacific (e.g., Umezawa et al 2018). ln order to further investigate the Indonesian fire emissions, we focus on the CO seasonal cycles in the SH.…”

“…This result strongly suggests that climate-CO relationship may be different between 1997 and other years. Climate can influence atmospheric CO via process-based emission impacts both near and distant to Indonesia, combined with impacts on transport and photochemistry (e.g., Rowlinson et al 2019).…”