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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D20213, doi:10.1029/2006JD007086, 2006

Polar mesospheric clouds observed by an iron Boltzmann lidar at Rothera (67.5°S, 68.0°W), Antarctica from 2002 to 2005: Properties and implications

Xinzhao Chu

Cooperative Institute for Research in Environmental Sciences and Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, USA


Patrick J. Espy

Physical Sciences Division, British Antarctic Survey, Cambridge, UK


Graeme J. Nott

Physical Sciences Division, British Antarctic Survey, Cambridge, UK


Jan C. Diettrich

Physical Sciences Division, British Antarctic Survey, Cambridge, UK


Chester S. Gardner

Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Abstract

Lidar observations of polar mesospheric clouds (PMC) were made at Rothera, Antarctica, from December 2002 to March 2005. Overall, 128 hours of PMC were detected among the 459 hours of observations, giving a mean occurrence frequency of 27.9%. The mean PMC centroid altitude is 84.12 ± 0.12 km, the mean PMC total backscatter coefficient is 2.34 ± 0.11 × 10−6 sr−1, and the mean layer RMS width is 0.93 ± 0.03 km. The distribution of PMC centroid altitudes over all observations is symmetric (nearly Gaussian), with the most probable altitude (∼84 km) near the center of the distribution. The distribution of PMC brightness is non-Gaussian and is dominated by weak PMC. The observed PMC altitudes at Rothera support the earlier lidar findings that Southern Hemispheric PMC are on average 1 km higher than corresponding Northern Hemispheric PMC, and higher PMC occur at higher latitudes. Significant interannual and diurnal variations are observed in PMC centroid altitude and brightness. Mean PMC altitude varies more than 1 km from one year to another. In addition, 24-hour, 12-hour, and 8-hour oscillations are clearly shown in PMC centroid altitude and brightness. The altitude distribution of PMC brightness peaks at a nearly constant altitude of 84 km, with weaker PMC found on either side of this altitude. The mean PMC altitudes averaged in brightness bins are anticorrelated with the PMC brightness, where weaker PMC occur at higher altitude and the PMC altitudes are proportional to the logarithm of the PMC brightness.

Received 15 January 2006; accepted 30 June 2006; published 31 October 2006.

Keywords: polar mesospheric clouds; lidar; NLC microphysics.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere: composition and chemistry; 3334 Atmospheric Processes: Middle atmosphere dynamics (0341, 0342); 3360 Atmospheric Processes: Remote sensing.

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Citation: Chu, X., P. J. Espy, G. J. Nott, J. C. Diettrich, and C. S. Gardner (2006), Polar mesospheric clouds observed by an iron Boltzmann lidar at Rothera (67.5°S, 68.0°W), Antarctica from 2002 to 2005: Properties and implications, J. Geophys. Res., 111, D20213, doi:10.1029/2006JD007086.