Depletion and Recovery of the Ozone Layer Observed from Space Over the Past 5 0 years of the Anthropocene

This year we are celebrating the 50th anniversary of the launch of the backscatter UV (BUV) instrument on NASA's Nimbus-4 satellite. Since then 10 more advanced instruments, but based on the same basic measurement principle, have been launched on polar orbiting NASA and NOAA satellites. The datasets produced by these instruments are unique for they have captured the period before the onset of the decline of the ozone layer due to manmade chemicals, the declining period, and the present slow recovery period. This period includes the rapid development of the iconic anthropocene era feature called the "Ozone Hole" . However, stitching together data from 11 separate satellite instruments to create a homogeneous record has presented many challenges. The first two NASA instruments suffered considerable degradation after launch that required the development of novel techniques to characterize their calibration. The next 7 instruments were launched on NOAA's polar orbiting weather satellites that were not designed for long-term monitoring of climate variables. In particular, they didn't have the station keeping capabilities needed to maintain a stable equator crossing time. Drifting orbits not only stress the retrieval algorithm and the calibration system of UV instruments but also make the interpretation of data difficult because the upper stratospheric ozone has systematic and complex diurnal variabilities that are comparable to the anthropogenic signal one wants to extract. We will highlight our recent efforts in untangling this knot. Finally, we will discuss the results from the OMPS limb scattering instrument, a recent addition to this constellation, that has been operating on the Suomi NPP satellite since October 2011. It is helping us capture how the ozone layer in the lower stratosphere and troposphere is evolving in response to the climate change and rising chemical pollutants in some parts of the world, while the upper stratosphere slowly recovers due to phaseout of the chemicals that initiated the decline of the ozone layer in the late 70s.