Search

In this work, we investigated the seasonal cycle of atmospheric potential oxygen (APO), a unique tracer of air‐sea gas exchanges of molecular oxygen (O2) and carbon dioxide (CO2), expressed as APO = O2 + 1.1 × CO2. APO data were obtained from flask air samples collected since the late 1990s at three Japanese ground stations and on commercial cargo ships sailing between Japan and Australia/New Zealand, North America, and Southeast Asia. We also analyzed the APO spatial distribution and seasonal cycles with simulations from an atmospheric transport model using climatological oceanic O2 fluxes from an empirical product that relate O2 flux to ocean heat as input. Model simulations reproduced the observed APO seasonal cycles generally well, but with larger amplitudes and earlier occurrence of seasonal minima and maxima than in the observations. Moreover, the observed seasonal cycles exhibited larger APO enhancements than the simulations in autumn and early winter, especially in the North Pacific at 20°N–60°N. These enhancements remained when refining the comparison by adjusting the simulated APO peak‐to‐peak amplitudes and seasonal phases to the observations. This suggests additional O2 emissions in the North Pacific, not well expressed in the air‐sea O2 fluxes used as input for our model simulations. The average autumn enhancement at 40°N–60°N was approximately twice that measured at 20°N–40°N. Confirming previous studies, our results indicate two distinct mechanisms possibly contributing to the additional oceanic O2 emissions: outgassing from a subsurface shallow oxygen maximum at 20°N–40°N and autumn phytoplankton bloom at 40°N–60°N. Plain Language Summary: Seasonal variations of air‐sea molecular oxygen (O2) exchanges are mainly driven by spring/summer emission and autumn/winter absorption. Emission results mainly from O2 production by phytoplankton at the ocean surface; absorption is related to O2 uptake in deep oxygen‐depleted water layers caused by oceanic ventilation. A phytoplankton bloom in autumn and outgassing from water rich in dissolved O2 just below the mixed layer, known as the shallow oxygen maximum, have been suggested as possible mechanisms contributing to the O2 seasonal cycles. Unfortunately, these oceanic autumn O2 emissions are not well characterized. In this study, we analyzed air samples collected in the western and northern Pacific to evaluate the oceanic component of the O2 seasonal cycle, known as "atmospheric potential oxygen" and calculated as the sum of atmospheric O2 and carbon dioxide. By comparing these observations with model simulations that used previous air‐sea O2 flux estimates as input, we identified marked enhancements in autumn at latitudes between 20°N and 60°N in the Pacific. This corresponds to the geographic area where the autumn phytoplankton bloom and the shallow oxygen maximum occur. This result is a strong indication of additional autumn O2 emissions in the extratropical North Pacific. Key Points: We analyzed atmospheric potential oxygen (APO), a tracer of air‐sea exchanges of molecular oxygen (O2) and carbon dioxide, in the PacificThe observed seasonal APO enhancement at 20°N–60°N in autumn, relative to model simulations, suggests additional oceanic O2 emissionsOutgassing from a shallow oxygen maximum (20–40°N) and an autumn phytoplankton bloom (40–60°N) likely contribute to this enhancement [ABSTRACT FROM AUTHOR]

Norihiko Tsuboi,1 Kaoru Tsuboi,1 Nobuyuki Nosaka,1,2 Nao Nishimura,1 Satoshi Nakagawa1 1Critical Care Medicine, National Center for Child Health and Development, Tokyo, Japan; 2Department of Intensive Care Medicine, Tokyo Medical and Dental University, Tokyo, JapanCorrespondence: Norihiko TsuboiCritical Care Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, JapanTel +81-334160181Fax +81-224162222Email tsuboi-n@ncchd.go.jpAbstract: Although the pathophysiology of chronic obstructive pulmonary disease (COPD) is multifactorial, central airway collapse is reported to have a great impact on symptom severity. In COPD patients, positive pressure formed by hyperinflated lungs compressing the tracheal wall and negative changes in intratracheal static pressure due to rapid expiratory flow velocity at the beginning of expiration collapse the trachea. This phenomenon can be explained by fluid dynamics theory. Our hypothesis is that ventilatory strategy focusing on minimization of expiratory flow rate may be advantageous for patients receiving mechanical ventilation for COPD. If appropriate counter pressure could be applied on exhalation, patients may be able to exhale slowly with reduced expiratory flow rates which may prevent negative changes of the intratracheal static pressure. We devised a new conceptual ventilation mode “minimized expiratory flow rate ventilation (MExV)” which applies regulated counter pressure on exhalation. The conceptual waveforms of “minimized expiratory flow rate ventilation” including flow rate, volume, and airway pressure are shown, compared with typical waveforms of the conventional ventilation modes.Keywords: COPD, tracheomalacia, fluid dynamics, minimized expiratory flow rate ventilation, flow-controlled ventilation

We describe a method for removing systematic biases of column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) derived from short-wavelength infrared (SWIR) spectra of the Greenhouse gases Observing SATellite (GOSAT). We conduct correlation analyses between the GOSAT biases and simultaneously retrieved auxiliary parameters. We use these correlations to bias correct the GOSAT data, removing these spurious correlations. Data from the Total Carbon Column Observing Network (TCCON) were used as reference values for this regression analysis. To evaluate the effectiveness of this correction method, the tnzuncorrected/corrected GOSAT data were compared to independent XCO2 and XCH4 data derived from aircraft measurements taken for the Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) project, the National Oceanic and Atmospheric Administration (NOAA), the US Department of Energy (DOE), the National Institute for Environmental Studies (NIES), the Japan Meteorological Agency (JMA), the HIAPER Pole-to-Pole observations (HIPPO) program, and the GOSAT validation aircraft observation campaign over Japan. These comparisons demonstrate that the empirically derived bias correction improves the agreement between GOSAT XCO2/XCH4 and the aircraft data. Finally, we present spatial distributions and temporal variations of the derived GOSAT biases.