Vertical profiles in NO3 and N2O5 measured in-situ from the NOAA P-3 aircraft: An investigation of the coupling between atmospheric stratification and nighttime chemical transformation

Vertical stratification and reduced mixing in the lower troposphere at night has implications for chemical transformations of ozone, nitrogen oxides, VOC and aerosol. For example, daytime photochemical ozone formation tends to occur within a deeper and better mixed layer than does nighttime nitrogen oxide chemistry that tends to destroy ozone. This contribution presents nighttime vertical profiles of NO3, N2O5, NO2, O3, VOC and aerosol measured from the NOAA P-3 aircraft during recent field campaigns. Profiles obtained from ascents and descents upon takeoff, landing or missed approaches to airfields penetrated the shallow nocturnal boundary layer and showed sharp contrasts between this layer and the residual daytime boundary layer above it. In some cases, multiple additional layer structure was apparent. Nighttime profiles over the ocean off of the New England coast during the NEAQS 2004 campaign reached as low as the nocturnal marine boundary layer in only a few cases, but could be compared to surface measurements on the NOAA R/V Ronald H. Brown or on islands near the coast. Finally, profiles from near the surface to altitudes as high at 3.5 km illustrated the difference between nighttime chemistry occurring within the residual daytime boundary layer and the free troposphere. The residual layer often showed the signature of photochemistry from the previous day, but also showed evidence for rapid nighttime chemical reactions within vertically stratified urban and power plant plumes.