RETRIEVAL OF FORMALDEHYDE FROM HIGH-RESOLUTION MIPAS-ENVISAT SPECTRA

摘要

The Fourier transform spectrometer MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) on Envisat measures infrared emission of the Earth's atmosphere in a limb viewing mode. Vertical profiles of temperature and numerous trace gases are retrieved with the IMK science-oriented processor. The main sources of formaldehyde (CH{sub}2O) in the troposphere are methane oxidation, biomass burning and biogenic emissions while it is destroyed via photolysis and reaction with OH. In the stratosphere, the CH{sub}2O profile results from an equilibrium between production by methane oxidation and destruction as described above. In the mid-infrared, formaldehyde shows weak emission lines between 1000 and 1800 cm{sup}(-1) with the most prominent band centred around 1750 cm{sup}(-1) which is used in the retrieval based on new spectroscopic data. Analysis of CH{sub}2O averaging kernels demonstrates sensitivity from the upper troposphere to the stratopause with 1 to 5 independent pieces of information depending on latitude and number of cloud-free tangent altitudes. Preliminary retrieval results show mean CH{sub}2O maxima in the upper tropical troposphere and in the upper stratosphere in the order of 100 to 150 pptv.