Investigation of Mesospheric Metal Emission Signals from SCIAMACHY Limb Measurements
Abstract
This project developed and tested a novel retrieval algorithm to investigate mesospheric metal emission signals from SCIAMACHY limb measurements. The spectra from the SCIAMACHY limb MLT measurements (from 2008-2012) revealed number densities for several metal atom and ion species (Mg, Mg+ and Na). Through advancements in the retrieval algorithms such as the addition of a ring effect correction and the treatment of self-absorption, high-resolution features in the spectra, like fully resolved Fraunhofer lines in the solar spectrum, spectral shifts and splittings due to hyper-fine structure, Doppler effect, and isotopic compositions are now possible. As a result, the Mg vertical profiles do not show a second maximum at 70km anymore and through the improved resolution in the peak region of the metal atom and ion layers a clear latitudinal dependence of the Mg+ peak altitude could be observed for the first time. Furthermore, a treatment of multiple scattering effects extended the retrieval algorithm to derive Na densities. Knowing the global mesospheric metal density distribution, combined with models, including reaction rates of loss processes as well as the meteoric composition and fraction ablated in the upper atmosphere, enables estimating the daily input of meteoric material to the earth atmosphere. The knowledge won from the MLT dataset can be used to reanalyze the nominal limb and nadir dataset, e.g. as a priori information in the retrieval and the potential of the SCIAMACHY dataset is still not fully exhausted. An accurate neutral and ionized metals global data set is now available for the period 2008 to 2012. These data have been compared with a 2D photochemical/dynamical model for Mg and Mg+ showing that there are differences between model and data for Mg on a seasonal basis even though Mg+ model and data are in agreement. The data show clearly significant transport of both Mg and Mg+ above 100km in both the polar and equatorial regions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 31, 2013
- Accession Number
- ADA593869
Entities
People
- Art C. Aikin
- Christian Von Savigny
- John P. Burrows
- Martin Langowski
Organizations
- University of Bremen