Photofragmentation two‐photon laser‐induced fluorescence detection of NO2 and NO: Comparison of measurements with model results based on airborne observations during PEM‐Tropics A

Measurements of NO and NO2 are reported using a highly modified photofragmentation two‐photon laser‐induced fluorescence (PF‐TP‐LIF) instrument. Available evidence suggests that the changes made substantially reduced wall decomposition of labile NOy species. In sharp contrast to the results reported from NASA's 1991 PEM‐West A program where the median value for the ratio (NO2)meas/(NO2)calc was 3.36, the PEM‐Tropics A observations produced a value for this ratio of 0.93. This represents the first time that remote upper tropospheric NO‐NO2 data have shown a high degree of correspondence with current photochemical mechanisms.