Nitryl Chloride (ClNO2) from Sea to Shining Sea: A comparison of observations in the coastal Pacific and North Atlantic

Nitryl chloride (ClNO2) is an important nighttime reactive nitrogen reservoir and morning time oxidant source in polluted regions. In this presentation, observations made during two ship-based field campaigns are compared to assess causes for variability or lack thereof in the ClNO2 production efficiency within the marine boundary layer or coastal urban areas. During ICEALOT, ClNO2 was measured for several nights in spring of 2008 hundreds of kilometers downwind of the N. American continent. In contrast, during CALNEX, ClNO2 was observed primarily as a constituent of polluted urban air advected to the coastal marine boundary layer. These features are broadly consistent with persistent westerly flow, however, unique differences in the ClNO2 production efficiency per unit N2O5 reacted remain. These issues are explored using constraints from the reactive nitrogen budget, simple box models, and regional and global chemical transport models.