High Precision Measurements of Resonance Frequency of Ozone Rotational Transition J=61,5-60,6 in the Real Atmosphere

Ground-based passive measurements of downwelling atmospheric radiation at similar to 110.836 GHz allow extracting the spectra of ozone self-radiation (rotational transition J = 6(1,5)-6(0,6)) coming from the low stratosphere-mesosphere and retrieving vertical profiles of ozone concentration at these altitudes. There is a notable (several hundred kHz) ambiguity in the determination of the resonance frequency of this important ozone line. We carried out long-term ground-based measurements of atmospheric microwave radiation in this range using upgraded apparatus with high technical accuracy and spectral resolution (similar to 12 kHz). The obtained brightness temperature spectra allowed us to determine the frequency of this ozone line to be 110,835.909 +/- 0.016 MHz. We verified that the Doppler frequency shift by horizontal wind as well as the variations of the tropospheric absorption had little effect on the obtained result. The found value was 131 +/- 16 kHz less than that measured in the laboratory and differed from modern model calculations. At the same time, it was close to the results of early semiempirical calculations made more than 40 years ago. The applications where precise knowledge about the resonance frequency of this ozone line can be important were discussed in this paper.

Automated summary

Ground-based passive measurements were conducted to extract the spectra of ozone self-radiation and retrieve vertical profiles of ozone concentration in the low stratosphere-mesosphere. High technical accuracy and spectral resolution were achieved in the measurements, leading to the determination of the frequency of this ozone line to be 110,835.909 +/- 0.016 MHz.