Responses of polar mesospheric cloud brightness to stratospheric gravity waves at the South Pole and Rothera, Antarctica

• Published in: Journal of Atmospheric and Solar-Terrestrial Physics
• Other Authors: Chu, Xinzhao (author), Yamashita, Chihoko (author), Espy, Patrick (author), Nott, Graeme (author), Jensen, Eric (author), Liu, Han-Li (author), Huang, Wentao (author), Thayer, Jeffrey (author)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Ltd. 2009
• Subjects: Polar mesospheric clouds; Gravity waves; Lidar; Antarctica; Stratosphere; Austral; Rothera; South Pole; Antarc*; South pole; W. Antarctica
• Online Access: http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-003-024; https://doi.org/10.1016/j.jastp.2008.10.002

We present the first observational proof that polar mesospheric cloud (PMC) brightness responds to stratospheric gravity waves (GWs) differently at different latitudes by analyzing the Fe Boltzmann lidar data collected from the South Pole and Rothera (67.5°S, 68.0°W), Antarctica. Stratospheric GW strength is characterized by the root-mean-square (RMS) relative density perturbation in the 30-45 km region and PMC brightness is represented by the total backscatter coefficient (TBC) in austral summer from November to February. The linear correlation coefficient (LCC) between GW strength and PMC brightness is found to be +0.09 with a 42% confidence level at the South Pole and -0.49 with a 98% confidence level at Rothera. If a PMC case potentially affected by a space shuttle exhaust plume is removed from the Rothera dataset, the negative correlation coefficient and confidence level increase to -0.61 and 99%, respectively. The Rothera negative correlation increases when shorter-period waves are included while no change is observed in the South Pole correlation. Therefore, observations show statistically that Rothera PMC brightness is negatively correlated with the stratospheric GW strength but no significant correlation exists at the South Pole. A positive correlation of +0.74 with a confidence level of 99.98% is found within a distinct subset of the South Pole data but the rest of the dataset exhibits a random distribution, possibly indicating different populations of ice particles at the South Pole. Our data show that these two locations have similar GW strength and spectrum in the 30-45 km region during summer. The different responses of PMC brightness to GW perturbations are likely caused by the latitudinal differences in background temperatures in the ice crystal growth region between the PMC altitude and the mesopause. At Rothera, where temperatures in this region are relatively warm and supersaturations are not as large, GW-induced temperature perturbations can drive subsaturation in the warm phase. Thus, GWs ...