RESUMO
We report airborne measurements of acetaldehyde (CH3CHO) during the first and second deployments of the National Aeronautics and Space Administration (NASA) Atmospheric Tomography Mission (ATom). The budget of CH3CHO is examined using the Community Atmospheric Model with chemistry (CAM-chem), with a newly-developed online air-sea exchange module. The upper limit of the global ocean net emission of CH3CHO is estimated to be 34 Tg a-1 (42 Tg a-1 if considering bubble-mediated transfer), and the ocean impacts on tropospheric CH3CHO are mostly confined to the marine boundary layer. Our analysis suggests that there is an unaccounted CH3CHO source in the remote troposphere and that organic aerosols can only provide a fraction of this missing source. We propose that peroxyacetic acid (PAA) is an ideal indicator of the rapid CH3CHO production in the remote troposphere. The higher-than-expected CH3CHO measurements represent a missing sink of hydroxyl radicals (and halogen radical) in current chemistry-climate models.
RESUMO
David Nance's photographs invite us to cross the liminal space between road and roadside and to consider the experience that trauma surgeons share with injured patients and the families of the injured and the dead. Just as trauma surgeons use the tools of science and surgery to make order out of the chaos of "the scene," so patients' families use art, found objects, and grief to transform anonymous roadsides into specific, personal remembrances. Bound together by the uncertainties of trauma, we can all stand at the side of the road bearing witness to both the inevitability and unpredictability of death.
