Statistics of sporadic iron and relation to atmospheric dynamics

At Rothera Research Station (67.3°S, 68.1°W), Antarctica, 296 h of day and nighttime Fe-Boltzmann temperature lidar data were accumulated in 2003. During this time, sporadic iron layers (FeS) were observed with an annual average occurrence probability of 14%. The peak altitude of the FeS layers was highest during the summer, with a fitted value of 103 km while during the winter the layer decreased in height to 90 km with an annual average of 97 km. The atmospheric temperature perturbations and potential energy density profiles computed from the same lidar data exhibited increased temperature but constant-with-height potential energy density when sporadic Fe layer occurred. Once sporadic Fe layers disappeared, the potential energy density decreased with height, indicating an energy loss due to atmospheric gravity wave breaking. These results suggest a link between FeS and atmospheric dynamics

Lidar observations of polar mesospheric clouds at Rothera, Antarctica (67.5 degrees S, 68.0 degrees W)

Polar mesospheric clouds (PMC) were observed by an Fe Boltzmann temperature lidar at Rothera (67.5degreesS, 68.0degreesW), Antarctica in the austral summer of 2002-2003.The Rothera PMC are much weaker, less frequent, and not as high as the PMC observed at the South Pole. The mean PMC altitude is 83.74 +/- 0.25 km, which is approximately 1.3 km lower than the South Pole clouds. A comparison of numerous cloud observations indicates that southern hemisphere PMC are about 1 km higher than northern clouds at similar latitudes. Lidar measurements also show that the mesopause region temperatures at Rothera in late January are warmer than at the South Pole, while the Fe layer at Rothera has higher density and a lower peak altitude compared to the summertime Fe layer at the South Pole. These Fe density and temperature observations are qualitatively consistent with the PMC observations

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

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