Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 35, 295-309, 2017
http://www.ann-geophys.net/35/295/2017/
doi:10.5194/angeo-35-295-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Regular paper
28 Feb 2017
Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM
Haiyang Gao1,2, Gordon G. Shepherd3, Yuanhe Tang4, Lingbing Bu1,2, and Zhen Wang1,2 1Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing, China
2School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing, China
3Centre for Research in Earth and Space Science, York University, Toronto, Canada
4School of Science, Xi'an University of Technology, Xi'an, China
Abstract. Double-layer structures in polar mesospheric clouds (PMCs) are observed by using Solar Occultation for Ice Experiment (SOFIE) data between 2007 and 2014. We find 816 and 301 events of double-layer structure with percentages of 10.32 and 7.25 % compared to total PMC events, and the mean distances between two peaks are 3.06 and 2.73 km for the Northern Hemisphere (NH) and Southern Hemisphere (SH) respectively. Double-layer PMCs almost always have less mean ice water content (IWC) than daily IWC during the core of the season, but they are close to each other at the beginning and the end. The result by averaging over all events shows that the particle concentration has obvious double peaks, while the particle radius exhibits an unexpected monotonic increase with decreasing altitude. By further analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. 56.00 and 47.51 % of all double-layer events for the NH and SH respectively have temperature enhancements larger than 2 K locating between their double peaks. The longitudinal anti-correlation between the gravity waves' (GWs') potential energies and occurrence frequencies of double-layer PMCs suggests that the double-layer PMCs tend to form in an environment where the GWs have weaker intensities.

Citation: Gao, H., Shepherd, G. G., Tang, Y., Bu, L., and Wang, Z.: Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM, Ann. Geophys., 35, 295-309, doi:10.5194/angeo-35-295-2017, 2017.
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We find double-layer structure events with percentages of 10.32 and 7.25 % compared to total PMCs events, and the mean distances between two peaks are 3.06 and 2.73 km for the NH and SH respectively using SOFIE data from 2007 to 2014. By analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. These structures have close relationships with temperature enhancements and GWs.
We find double-layer structure events with percentages of 10.32 and 7.25 % compared to total...
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