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

Abstract

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. © 2007 COSPAR.