Deep vertical propagation of mountain waves above Scandinavia

Abstract:

The project "Investigation of the life cycle of gravity waves"
(GW-LCYCLE) is part of the German research initiative ROMIC (Role of the
Middle atmosphere In Climate) funded by the ministry of research. In
close cooperation with Scandinavian partners as the Stockholm University
and the Finnish Meteorological Institute a first field phase was
conducted in November/December 2013. The field program combined
ground-based observations of tropospheric and lower stratospheric flow
and stratospheric and mesospheric temperature by lidars and radars at
Alomar (N) and at Esrange (S) with airborne and balloonborne
observations. Northern Scandinavia was chosen since the westerly flow
across the mountains is often aligned with the polar night jet
permitting gravity waves (GWs) to propagate into the middle atmosphere.

From 2 until 14 December 2013, 24 flight hours of the DLR Falcon flown
in four intensive observing periods (IOPs) provided in-situ and
remote-sensing observations of atmospheric wind, temperature, water
vapour and other trace gases (e.g. CO, N2O, O3) in the vicinity of the
tropopause. During three IOPs, the airborne observations were supported
by 3 hourly simultaneous radiosonde launches from Andøya (N), Esrange
(S) and Sodankylä (FIN). Additionally, 1.5 hourly high-frequency
radiosonde launches were conducted from the Arena Arctica at Kiruna
airport with two systems (Väisälä and GRAW)and different balloon
fillings to obtain different ascent rates.

During GW-LCYCLE, the atmospheric flow above the Scandinavian mountains
was observed under distinct meteorological conditions enabling or
attenuating the deep vertical propagation of mountain-induced gravity
waves. The presentation juxtaposes two different cases and analyses the
associated meteorological conditions. The unique combination of airborne
tropospheric wind lidar measurements, flight level data, high-frequency
radiosonde profiles and the ground-based lidar observations allow a
comprehensive study of deeply propagating gravity waves from the Earth’s
surface to the mesosphere.