From TOMS to OMI Reflections on 15 years of NASA/KNMI/FMI Collaboration Pawan K Bhartia Earth Sciences Division- Atmospheres NASA Goddard Space Flight Center Greenbelt, Maryland, USA

First image of the Antarctic Ozone hole. This image was produced from the TOMS data in 1984, and was first published in NY Times in late ‘ 85. Subsequently, images like this appeared in magazines and newspapers all over the world. A rare splitting of the Antarctic ozone hole captured by TOMS in The split occurred because of the splitting of the polar vortex (circumpolar winds).

A small sample from diverse range of of publications with TOMS-produced images on the cover

Total amount of sulfur dioxide injected into the atmosphere by over 100 volcanoes. These estimates, made using a series of TOMS instruments, are the only data of its kind. SO2 from El Chichon Volcano

Smoke from Colorado fires (June 25, 2002) Transport of Mongolian dust to N. America in April This image was made by compositing several days of TOMS data. These ingenious images of dust and smoke transport across countries and continents were produced by the TOMS team from the “ residuals ” after the cloud, surface, and ozone effects were properly removed from the data. This method has now become a well established technique to study aerosol transport.

Estimation of cancer-causing UVB using TOMS data Global map of surface UVB produced by the TOMS team. Data quality is comparable to the best ground-based stations except that TOMS cannot see localized depressions in UVB caused by urban pollution due to its large ~100 km pixel size. Comparison of TOMS-derived UVB (symbols) with an accurate ground-based instrument (lines). The good clear-sky comparison (upper curve) was an expected result, but similar results under all-sky conditions (lower curve) were quite unexpected.

Tropospheric ozone constitutes only 10% of the total ozone column, yet it is an important greenhouse gas and is responsible for cleansing the atmosphere of pollutants. Near the surface ozone is harmful to human health and biological productivity. The TOMS team developed an innovative technique called “ cloud slicing ” to extract these weak signals from the data. These two panels show comparison between TOMS data (solid line) and accurate measurements of tropospheric column ozone made using balloon-borne instruments at two locations (symbols).

Improvements of OMI over TOMS OMI pixels are more than an order of magnitude smaller in area –increases sensitivity to small volcanic events and aerosol plumes OMI has more wavelengths with higher spectral resolution –Provides order of magnitude higher sensitivity sensitivity to volcanic SO 2 and allows development of boundary layer products OMI instrument has degraded far less than any instrument of similar type

Benefits to the Three Participating Institutions NASA has been able to continue and enhance the TOMS record and was able to move into tropospheric chemistry research. KNMI is now one of the leading institutions in the world in this field. FMI has moved from UVB to broader area of atmospheric chemistry research

But Most Importantly! OMI has brought together scientists from three countries and other institutions that have worked well with each other over the past decade. I hope that this collaboration will continue with Sentinel 5p/TropOMI and future missions Though I will only be watching from the sidelines!