Vertical nitrogen dioxide and ozone concentrations measured from a tethered balloon in the Lower Fraser Valley

A series of vertical profiles of temperature, relative humidity, NO2 and O3 were determined in the Lower Fraser Valley, British Columbia, as part of the PACIFIC ʹ93 field study. Data from one day show very structured vertical distributions of all parameters in the morning, as expected from the limited vertical mixing under the nocturnal inversion. NO2 concentrations of 20 ppbv were observed 300m above the surface, while the surface concentrations were 2 ppbv. Ozone and nitrogen oxide chemistry were observed at all altitudes throughout the PBL. Titration of O3 by NO to produce NO2 was observed in layers above the ground, under the influence of the NBL. An increase in odd oxygen throughout the PBL, during the morning and early afternoon, shows “smog chemistry” is occurring even though the ground-based O3 measurements suggest this day was not particularly chemically active. However, once the NBL has dissipated, the ground-based measurements seem representative of the entire PBL.