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Volume 16, issue 19
Atmos. Chem. Phys., 16, 12587-12600, 2016
https://doi.org/10.5194/acp-16-12587-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 12587-12600, 2016
https://doi.org/10.5194/acp-16-12587-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 10 Oct 2016

Research article | 10 Oct 2016

The relationship between polar mesospheric clouds and their background atmosphere as observed by Odin-SMR and Odin-OSIRIS

Ole Martin Christensen1,2, Susanne Benze2, Patrick Eriksson1, Jörg Gumbel2, Linda Megner2, and Donal P. Murtagh1 Ole Martin Christensen et al.
  • 1Department of Earth and Space Sciences, Chalmers University of Technology, Gothenburg 41296, Sweden
  • 2Department of Meteorology, Stockholm University, Stockholm 11296, Sweden

Abstract. In this study the properties of polar mesospheric clouds (PMCs) and the background atmosphere in which they exist are studied using measurements from two instruments, OSIRIS and SMR, on board the Odin satellite. The data comes from a set of tomographic measurements conducted by the satellite during 2010 and 2011. The expected ice mass density and cloud frequency for conditions of thermodynamic equilibrium, calculated using the temperature and water vapour as measured by SMR, are compared to the ice mass density and cloud frequency as measured by OSIRIS. We find that assuming thermodynamic equilibrium reproduces the seasonal, latitudinal and vertical variations in ice mass density and cloud frequency, but with a high bias of a factor of 2 in ice mass density.

To investigate this bias, we use a simple ice particle growth model to estimate the time it would take for the observed clouds to sublimate completely and the time it takes for these clouds to reform. We find a difference in the median sublimation time (1.8h) and the reformation time (3.2h) at peak cloud altitudes (82–84km). This difference implies that temperature variations on these timescales have a tendency to reduce the ice content of the clouds, possibly explaining the high bias of the equilibrium model.

Finally, we detect and are, for the first time, able to positively identify cloud features with horizontal scales of 100 to 300km extending far below the region of supersaturation ( > 2km). Using the growth model, we conclude these features cannot be explained by sedimentation alone and suggest that these events may be an indication of strong vertical transport.

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This study investigates the properties of ice clouds forming in the upper summer mesosphere known as polar mesospheric clouds, and their relationship with the background atmosphere combining two different satellite instruments. We find that temperature variations in the atmosphere of the order of some hours reduce the amount of ice in these clouds and see indications of strong vertical transport in these clouds.
This study investigates the properties of ice clouds forming in the upper summer mesosphere...
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