Chemical heating rates derived from SCIAMACHY vibrationally excited OH limb emission spectra Original Research Article

The SCIAMACHY instrument on board Envisat is able to measure nearly all vibrational transitions of mesospheric hydroxyl – from the ultraviolet to the near infrared spectral region. In this paper, we analyze SCIAMACHY limb emission data in the 1000–1750 nm spectral region by means of a new vibrational non-LTE model of OH. Several hydroxyl hotbands are identified. Vibrational non-LTE model calculations applying different collisional relaxation models are able to reproduce the measured spectra. Best agreement between model calculations and measured spectra is obtained, if a combination of multiquantum and step ladder single-quantum relaxation model is applied. Emissions from the OH(v = 9) vibrational state are used to derive chemical heating rates from the SCIAMACHY spectra. Instantaneous heating rates are in the order of 10 K/day. Article Outline