A global model of meteoric metals

Wuhu Feng1,2*, John Plane1, Martyn Chipperfield2, Daniel Marsh3, Diego Janches4, Erin Dawkins1,2,Josef Hoffner5, Fan Yi6, Chester Gardner7, Jonathan Friedman8, Jonas Hedin9

1 School of Chemistry, University of Leeds, UK 2 NCAS, School of Earth and Environment, University of Leeds, UK

3 National Center for Atmospheric Research, USA 4 Space Weather Lab, GSFC/NASA, USA 5 Leibniz-Institute of Atmospheric Physics, Germany 6

School of Electronic Information, Wuhan University, China 7 University of Illinois at Urbana Champaign, USA 8 Arecibo Observatory, Puerto Rico

9 Department of Meteorology, Stockholm University, Sweden w.feng@leeds.ac.uk; J.M.C.Plane@leeds.ac.uk; m.chipperfield@leeds.ac.uk; marsh@ucar.edu

The mesosphere lower thermosphere (MLT) region connects the atmosphere below with space above. Therefore, it is affected by climate change and solar variability. One unique feature in the MLT is the presence of layers of metal atoms produced by meteoric ablation. We have developed the first global model of meteoric metals in the atmosphere by combining three components: the Whole Atmosphere Climate Community Model (WACCM), a description of the neutral and ion-molecule chemistry of six metals (Na, Fe, K, Mg, Ca and Si) and a treatment of the injection of meteoric constituents into the atmosphere. Here we report the performance of this new model by comparing different observations and show how the metal layers offer a unique way to understand the coupling of atmospheric chemistry and dynamical processes, as well as testing the accuracy of climate models in the MLT.

2. Processes controlling atmospheric metals1. Introduction

4. Computationally Efficient High Resolution Model

3. Model strategy

4. Atmospheric Na

Fig.1. Satellite measured Na total abundance compared with the model. This shows the Na layer has latitudinal and seasonal variations. The model captures the observed maximum winter and minimum summer Na abundance.

Fig. 2 . Annual mean profiles of temperature and Fe from lidar measurements and the model. Also shown are the simulated Fe from a 1D model and other iron constituents from the 3D model. It shows the peak of Fe layer and density and the distributions of Fe-bearing species in the MLT region. Fe+ ions dominate on the top-side of the Fe layer while (FeOH)2, FeOH and Fe(OH)2 are the major reservoirs on the underside of the layer.

7. Tides impact on mesospheric metals 8. Solar cycle impact

Fig. 5 Time series of anomaly of solar flux and modelled K abundance from 1955-2006. It is clearly seen anti-correlation between solar flux and K total column abundance. It also shows the increased K trend in the MLT.

References:

Feng W., D.R. Marsh, M.P. Chipperfield, D. Janches, J. Hoffner, F. Yi and J. M. C. Plane, A global atmospheric model of meteoric iron, J. Geophys. Res., Submitted.Marsh D., D. Janches, W. Feng, and J.M. C. Plane, A global model of meteoric sodium, J. Geophys. Res., Submitted.

5. Iron species in the atmosphere 6. Potassium layer

Fig. 3 . Monthly mean observed (top) and modelled potassium density profiles at Arecibo (18oN). This shows K has a summer maximum abundance, which is different to other metals (e.g., Na in Fig.1).

Fig.4: Three days of modelled temperature and Fe mixing ratio, as well as their perturbations, sampled every 30 minutes for Urbana (40oN). This shows Fe has diurnal variations, and the atmospheric tides have significant influences on Fe around the layer peak.

9. Summary and conclusion

The first global model of meteoric metals (Na, Fe, K, Mg, Ca and Si) in the atmosphere has been developed. The metal layers offer a unique way to understand the coupling of atmospheric chemistry and dynamical processes, as well as testing the accuracy of climate models in the MLT. For example, the model captures the seasonality of atmospheric metals, layer peaks and total column abundances, tidal and solar cycle impacts on the metals. This study enables us to connect the astronomy and atmospheric sciences.Investigating different metals in the same model allows us to better understand the astronomy, chemistry and physical processes controlling mesospheric metals.

Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds

Red boxes: Phenomena to be studied; Blue boxes: Observations constrain the models; Yellow box: The model structure for studying the whole atmospheric processes. Green: Laboratory measurements.