Metals in the Mesosphere: Meteoroids, Satellite Retrievals and Modelling.
Dawkins, Erin¹; Plane, John¹; Chipperfield, Martyn¹; Feng, Wuhu¹; Gumbel, Jörg²; Hedin, Jonas²; Friedman, Jonathon^3
1University of Leeds, UNITED KINGDOM; ²Stockholm University, SWEDEN; ³Arecibo Observatory, PUERTO RICO

Changes in the mesosphere are an important signal of climate change and there is increasing evidence that accurate simulations of changes to the Earth’s climate require models with a well resolved and accurate stratosphere and mesosphere. Following the ablation of meteoroids, the resulting metal species which are injected into the mesosphere/lower thermosphere region (80-110 km) offer a unique way of observing this region and of testing the accuracy of climate models in this domain.

A sodium retrieval algorithm first developed by Gumbel et al. (2007, GRL) has been extended, and modified to retrieve iron and potassium densities using data from the OSIRIS spectrometer on-board the Odin satellite. Here we present an overview of the new potassium retrieval scheme, along with the first ever climatology of the global potassium layer from space for 2002-2011. These layers have been validated using lidar data and successfully capture the unusual semi-annual seasonal behaviour of potassium which is starkly different to the other metals. Unlike sodium and iron which both display early wintertime density maxima, potassium also displays a summertime maximum which points to some unique and surprising features in the chemistry and the way it interacts with other atmospheric species. A detailed potassium chemistry scheme, developed by a team at Leeds (modules for Na, Fe, Ca and Mg already added), has now been included in a version of the NCAR Whole Atmosphere Community Climate Model (WACCM). The annual, latitudinal and long-term variation of these modelled potassium layers are compared with the retrieved datasets to evaluate model chemistry and dynamics.