Space-Based Measurement of Chemical Tracers (gaseous) and Aerosol Pollutants: Past, Present, and Future Needs (Core Science Keynote)

Space-based measurements of ozone from space started nearly half a century ago. The early instruments were primarily designed to develop space-based technology and were largely derived from ground-based remote-sensing instruments, such as the Dobson spectrophotometer developed about a century ago. However, over the years, spurred by funding from the Clean Air Act and scientific and environmental need to monitor the health of the ozone layer, instruments and numerical models of increasingly greater sophistication have been built.  This led to the phase out of many offending chemicals and caused retooling of a multi-billion dollar chemical industry. With clear indication that the ozone layer has stabilized with hints of a recovery there is high confidence that the key chemical and radiative processes in the stratosphere are now well understood. Therefore, the focus of this community is now shifting to measuring climate-sensitive gases that include greenhouses gases (tropospheric CO₂, CH₄ and O₃), chemical tracers for monitoring changes in the  meridional circulation due to climate change, and evolution of stratospheric aerosols produced by volcanoes and other sources of SO₂.  In the meantime technological enhancements have made it possible to measure boundary layer trace gases and aerosols from space that include five of the six EPA’s criteria pollutants, viz, particulate matter (PM), O₃, SO₂, NO₂, and CO as well as other trace gases such as ammonia, formaldehyde, glyoxal and BrO that are useful for understanding the underlying chemical processes that generate pollution. The growth of this field remains strong with several new missions planned to improve spatial resolution to isolate urban scale pollution sources and higher temporal resolution for monitoring regional transport of pollutants. In my talk I will track how the space-based community has responded to the changing scientific and environmental needs of measuring atmospheric trace gases and aerosols over the past 4 decades, and how this effort is being increasingly globalized with emerging technical powers from Asia joining the US and Europe in this endeavor.