Atmospheric NO₃, 3. Sunrise disappearance and the stratospheric profile

New ground-based measurements of NO₃ absorption in the band near 662nm were carried out using the moon as a light source during sunrise on July 1, 1988. As the sun rose, the observed slant column abundance of atmospheric NO₃ decreased systematically. This time-dependent decrease is expected, due to the progression of the solar terminator down through the atmosphere, and provides a basis for inferring the nighttime vertical profile of NO₃. This approach represents a new means of measuring the vertical profile of stratospheric species whose distributions change rapidly at sunrise. The profile inferred from the time-dependent NO₃ decrease is sensitive to the NO₃ absorption cross section and the adopted photolysis rate, and these sensivities are investigated. The inferred vertical profile on July 1, 1988, is in excellent agreement with theoretical predictions in the altitude range from about 20 to 33km. -from Authors