It is shown that the vibrational state population of stratospheric nitric oxide (NO) could be substantially different from that expected on the basis of local thermodynamic equilibrium (LTE). Deviations from LTE may arise because stratospheric NO can be photochemically produced from NO2 with several vibrational quanta. Model calculations suggest that the population of NO(υ = l) could be some 30% above that expected from LTE at 30 km with smaller enhancements above and below. Substantially larger enhancements are predicted for NO(υ = 2). This result is shown to have important implications for NO determination by remote sensing of IR emission. Data needed for the quantification of these effects are enumerated.
Jack A. Kaye and John B. Kumer, "Nonlocal thermodynamic equilibrium effects in stratospheric NO and implications for infrared remote sensing," Appl. Opt. 26, 4747-4754 (1987)