This title appears in the Scientific Report : 2018 
Mesoscale fine structure of a tropopause fold over mountains
Woiwode, Wolfgang (Corresponding author)
Dörnbrack, Andreas / Bramberger, Martina / Friedl-Vallon, Felix / Haenel, Florian / Höpfner, Michael / Johansson, Sören / Kretschmer, Erik / Krisch, Isabell / Latzko, Thomas / Oelhaf, Hermann / Orphal, Johannes / Preusse, Peter / Sinnhuber, Björn-Martin / Ungermann, Jörn
Stratosphäre; IEK-7
Atmospheric chemistry and physics, 18 (2018) 21, S. 15643 - 15667
Katlenburg-Lindau EGU 2018
10.5194/acp-18-15643-2018
Journal Article
Composition and dynamics of the upper troposphere and middle atmosphere
OpenAccess
OpenAccess
Please use the identifier: http://hdl.handle.net/2128/20308 in citations.
Please use the identifier: http://dx.doi.org/10.5194/acp-18-15643-2018 in citations.


We report airborne remote-sensing observations of a tropopause fold during two crossings of the polar front jet over northern Italy on 12 January 2016. The GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) observations allowed for a simultaneous mapping of temperature, water vapour, and ozone. They revealed deep, dry, and ozone-rich intrusions into the troposphere. The mesoscale fine structures of dry filaments at the cyclonic shear side north of the jet and tongues of moist air entraining tropospheric air into the stratosphere along the anticyclonic shear side south of the jet were clearly resolved by GLORIA observations. Vertically propagating mountain waves with recorded temperature residuals exceeding ±3K were detected above the Apennines. Their presence enhanced gradients of all variables locally in the vicinity of the tropopause. The combination of H2O − O3 correlations with potential temperature reveals an active mixing region and shows clear evidence of troposphere-to-stratosphere and stratosphere-to-troposphere exchange. High-resolution short-term deterministic forecasts of ECMWF's integrated forecast system (IFS) applying GLORIA's observational filter reproduce location, shape, and depth of the tropopause fold very well. The fine structure of the mixing region, however, cannot be reproduced even with the 9km horizontal resolution of the IFS, used here. This case study demonstrates convincingly the capabilities of linear limb-imaging observations to resolve mesoscale fine structures in the upper troposphere and lower stratosphere, validates the high quality of the IFS data, and suggests that mountain wave perturbations have the potential to modulate exchange processes in the vicinity of tropopause folds.