Large Midlatitude Stratospheric Temperature Variability Caused by Inertial Instability: A Potential Source of Bias for Gravity Wave Climatologies

• Published in: Geophysical Research Letters
• Main Authors: Rapp, M., Dörnbrack, A., Preusse, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: info:eu-repo/classification/ddc/550; polar night
• Online Access: https://juser.fz-juelich.de/record/857910; https://juser.fz-juelich.de/search?p=id:%22FZJ-2018-06864%22

Stratospheric temperature perturbations (TP) that have previously been misinterpreted as due to gravity waves are revisited. The perturbations observed by radio occultations during December 2015 had peak‐to‐peak amplitudes of 10 K extending from the equator to midlatitudes. The vertically stacked and horizontally flat structures had a vertical wavelength of 12 km. The signs of the TP were 180∘ phase shifted between equatorial and midlatitudes at fixed altitude levels. High‐resolution operational analyses reveal that these shallow temperature structures were caused by inertial instability due to the large meridional shear of the polar night jet at its equatorward flank in combination with Rossby wave breaking. Large stratospheric TP owing to inertial instability do frequently occur in the Northern Hemisphere (Southern Hemisphere) from October to April (April to October) in the 39 years of ECMWF Re‐Analysis‐Interim data. During 10% of the days, TP exceed 5 K (peak to peak).