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 NO 2 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 NO y species. In sharp contrast to the results reported from NASA's 1991 PEM‐West A program where the median value for the ratio (NO 2 ) meas /(NO 2 ) 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‐NO 2 data have shown a high degree of correspondence with current photochemical mechanisms.