AOSC Seminar
September 15, 2016

Satellite Retrievals of Air Quality and Climate Relevant Trace Gases at Goddard Space Flight Center

Nickolay Krotkov

Space-based monitoring plays an increasingly important role in the science of tropospheric chemistry and air quality applications to help mitigate anthropogenic and natural impacts on climate, sensitive ecosystems, and human health. The early space-based maps of ozone and volcanic SO2 were obtained from NASA’s Total Ozone Mapping Spectrometer (TOMS) on Nimbus-7, Metero-3, ADEOS and Earth Probe satellites. The next generation Ozone Monitoring Instrument (OMI) onboard NASA’s Aura satellite has been providing global observations of the ozone layer and key atmospheric pollutant gases, such as nitrogen dioxide (NO2) and sulfur dioxide (SO2), since October 2004. Our team at GSFC has been responsible for OMI standard SO2 and NO2 products. I will describe new OMI SO2 data re-processed with innovative data-driven Principal Component Analysis (PCA) retrieval algorithm. The algorithm has been applied to retrieve SO2 columns from the Ozone Mapping Profiling Suite on board NASA/NOAA Suomi National Polar Partnership satellite. Both OMI and OMPS provide highly consistent SO2 retrievals. I will describe on-going re-analysis of the TOMS volcanic SO2 data with the goal of creating multi-satellite longterm SO2 climate data record. I will also introduce a new version (V3) of the OMI NO2 Standard Product (OMNO2) based on new spectral fitting algorithm developed at GSFC. The new fitting algorithm results in 10-35% lower slant column retrievals as compared to the previous version. This results in smaller stratospheric column amounts, in better agreement with independent measurements over clean regions.

The analyses of OMI SO2 and NO2 observations have yielded profound insights into the spatial distribution and temporal trends in SO2 and NO2 pollution around the world. Over the eastern US, both NO2 and SO2 burdens decreased dramatically from 2005 to 2015, by more than 40 and 80%, respectively, as a result of both technological improvements and stricter regulations of emissions. OMI confirmed large reductions in SO2 over eastern Europe’s largest coal-fired power plants after installation of flue gas desulfurization devices, but increased pollution from Russian smelters. The North China Plain has the world’s most severe SO2 pollution, but a decreasing trend has been observed since 2011, with about a 50% reduction in 2012–2015, due to an economic slowdown and government efforts to restrain emissions from the power and industrial sectors. In contrast, India’s SO2 and NO2 levels from coal power plants and smelters are growing at a fast pace, increasing by more than 100 and 50%, respectively, from 2005 to 2015. The annual emissions from SO2 pollution sources were estimated using a new “top-down” algorithm that combines OMI measurements with wind data. The emission estimation algorithm can be also applied to NO2 observations and used to improve available emissions inventories, since some of the sources seen by OMI are not included in the traditional “bottom-up” inventories.