Articles | Volume 16, issue 11
Research article
03 Jun 2016
Research article |  | 03 Jun 2016

Measurements of global distributions of polar mesospheric clouds during 2005–2012 by MIPAS/Envisat

Maya García-Comas, Manuel López-Puertas, Bernd Funke, Á. Aythami Jurado-Navarro, Angela Gardini, Gabriele P. Stiller, Thomas von Clarmann, and Michael Höpfner

Abstract. We have analysed MIPAS (Michelson Interferometer for Passive Atmopheric Sounding) infrared measurements of PMCs for the summer seasons in the Northern (NH) and Southern (SH) hemispheres from 2005 to 2012. Measurements of PMCs using this technique are very useful because they are sensitive to the total ice volume and independent of particle size. For the first time, MIPAS has provided coverage of the PMC total ice volume from midlatitudes to the poles. MIPAS measurements indicate the existence of a continuous layer of mesospheric ice, extending from about  ∼ 81 km up to about 88–89 km on average and from the poles to about 50–60° in each hemisphere, increasing in concentration with proximity to the poles. We have found that the ice concentration is larger in the Northern Hemisphere than in the Southern Hemisphere. The ratio between the ice water content (IWC) in both hemispheres is also latitude-dependent, varying from a NH ∕ SH ratio of 1.4 close to the poles to a factor of 2.1 around 60°. This also implies that PMCs extend to lower latitudes in the NH. A very clear feature of the MIPAS observations is that PMCs tend to be at higher altitudes with increasing distance from the polar region (in both hemispheres), particularly equatorwards of 70°, and that they are about 1 km higher in the SH than in the NH. The difference between the mean altitude of the PMC layer and the mesopause altitude increases towards the poles and is larger in the NH than in the SH. The PMC layers are denser and wider when the frost-point temperature occurs at lower altitudes. The layered water vapour structure caused by sequestration and sublimation of PMCs is present at latitudes northwards of 70° N and more pronounced towards the pole. Finally, MIPAS observations have also shown a clear impact of the migrating diurnal tide on the diurnal variation of the PMC volume ice density.

Short summary
We have analysed IR measurements of PMCs in the NH and SH from 2005 to 2012. This technique is sensitive to the total ice volume independent of particle size. For the first time, we have measured the total ice volume from the midlatitudes to the poles. The data indicate a layer of ice from 81 to 89 km and from the poles to 50–60º in each hemisphere, increasing near the poles. The ice density is larger in the NH than in the SH and located 1 km lower. PMCs also show a diurnal variation.
Final-revised paper