The general goal of our research is to understand processes regulating the distribution of trace gases like ozone, methane, nitrogen oxides, and CO in the troposphere while improving satellite retrievals of these constituents. One activity consists of analysis and validation of satellite observations of atmospheric constituents from platforms like Aqua, Aura, Suomi-NPP. We also use models to compare to data, including Goddard chemistry-transport and chemistry-climate models like GMI, versions of WRF-Chem and the GEOS-5 Chemistry model. Currently there is opportunity for comparison of trends based on satellite and sounding data with retrospective model output. Major emphasis is placed on interpreting data collected in ground-based networks, eg, NDACC, SHADOZ (Southern Hemisphere Additional Ozonesondes; ), Pandora, AERONET, and from field experiments like DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality; ), SEAC4RS (Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys; ) and earlier campaigns like INTEX and ARCTAS. Examples of analyses include (1) comparison of ground-based data with satellite retrievals, eg, surface NO2 and OMI (Reed et al., 2013); (2) classification of vertical profiles from sondes and aircraft using self-organizing maps (Jensen et al., 2012; Stauffer et al., 2015), tracer correlations and laminar identification (Thompson et al., 2013); (3) analysis of processes affecting ozone, especially stratospheric intrusions and convection (Ott et al., 2015; Minschwaner et al., 2015). In some years, there may be an option to participate in field data collection.