Concerning the upper stratospheric gravity wave and mesospheric cloud relationship over Sondrestrom, Greenland

摘要

Recent research has shown experimental evidence that upper stratospheric gravity waves observed over Sondrestrom, Greenland (67°N, 310°E) portray a relationship with overlaying mesospheric clouds. It is the purpose of this paper to update the data from these studies with additional observations and reinvestigate the recently proposed hypothesis that suggests an anti-correlation between upper stratospheric gravity wave activity and mesospheric cloud strength. Data collected with the molecular/aerosol lidar at the ARCtic LIdar TEchnology (ARCLITE) facility in Sondrestrom have provided a total of 37 mesospheric cloud and upper stratospheric gravity wave observations from 1995-2001 that lend additional support to this hypothesis. We find a -0.44 linear correlation between the upper stratospheric gravity wave activity and the observed mesospheric cloud brightness within the 95% confidence interval. Even after considering geophysical variability due to observational limits, the linear correlation between the two fields is still -0.35 and also within a 95% confidence interval. These results suggest that there is indeed a statistically significant negative correlation between the upper stratospheric gravity wave activity and the mesospheric clouds. We then present two case studies from July 2001 that indicate that the upper stratospheric gravity wave activity leads the corresponding onset of mesospheric cloud activity with a time lag of ～ 1-4 h. Five additional data sets from 2001, which are not included here, are consistent with these lag values. The results support recent arguments for upper stratospheric gravity wave activity being related to mesospheric cloud characteristics (1) through the associated vertical group velocity propagation, (2) through a phase delay of the gravity wave field, or (3) through a spurious relationship with other gravity waves generated from a related source spectrum. In an effort to show causality, a scenario is proposed that relates the two phenomena and explains the physical nature of the mesospheric cloud-stratospheric gravity wave relationship.