Secondary 12?Day Planetary Wave in the Mesospheric Water Vapor During the 2016/2017 Unusual Canadian Stratospheric Warming

The anomalous strengthening of the stratospheric Aleutian High during early boreal winter 2016/2017 led to a rare Canadian warming (CSW) event, which extent wind reversal in Arctic region is strongest among CSWs since 2001. Unlike sudden warmings, polar vortex this CSW merely distorted, not displaced off pole or split into two pieces, and mean temperature only has modest increase few kelvins. Using Aura satellite Microwave Limb Sounder measurements, an exceptionally strong 12-day wave (12DW) with westward zonal wavenumber 1 captured mesospheric water vapor mixing ratio recovery phase CSW. Further diagnostic analysis suggests that baroclinic/barotropic instability related triggers 12DW stratosphere, meridional advection plays leading role modulation on vapor.