|
|
 |
|
|
Ann. Geophys., 24, 1189-1197, 2006
www.ann-geophys.net/24/1189/2006/
© European Geosciences Union 2006
The atmospheric background situation in northern Scandinavia during January/February 2003 in the context of the MaCWAVE campaign
U. Blum1,*, G. Baumgarten2, A. Schöch2, S. Kirkwood3, B. Naujokat4, and K. H. Fricke1
1Physikalisches Institut der Universität Bonn, 53115 Bonn, Germany
2Leibniz-Institut für Atmosphärenphysik e.V., 18225 Kühlungsborn, Germany
3Institutet för rymdfysik, 98 128 Kiruna, Sweden
4Meteorologisches Institut der Freien Universität Berlin, 12165 Berlin, Germany
*now at: Forsvarets forskningsinstitutt, 2027 Kjeller, Norway
Abstract. The atmosphere background wind field controls the propagation of
gravity waves from the troposphere through the stratosphere into the
mesosphere. During January 2003 the MaCWAVE campaign took place at
Esrange, with the purpose of observing vertically ascending waves
induced by orography. Temperature data from the U. Bonn lidar at
Esrange (68° N/21° E) and the ALOMAR RMR lidar
(69° N/16° E), wind data from Esrange MST radar
ESRAD, as well as wind data from the ECMWF T106 model, are used to
analyse the atmospheric background situation and its effect on
mountain wave propagation during January/February 2003. Critical
levels lead to dissipation of vertically ascending waves, thus
mountain waves are not observable above those levels. In the first
half of January a minor as well as a major stratospheric warming
dominated the meteorological background situation. These warmings
led to a wind reversal, thus to critical level filtering and
consequently prevented gravity waves from propagating to high
altitudes. While the troposphere was not transparent for stationary
gravity waves most of the time, there was a period of eight days
following the major warming with a transparent stratosphere, with
conditions allowing gravity waves generated in the lower troposphere
to penetrate the stratosphere up to the stratopause and sometimes
even into the lower mesosphere. In the middle of February a minor
stratospheric warming occurred, which again led to critical levels
such that gravity waves were not able to ascend above the middle
stratosphere. Due to the unfavourable troposphere and lower
stratosphere conditions for gravity wave excitation and propagation,
the source of the observed waves in the middle atmosphere is
probably different from orography.
Full Article in PDF (1119 KB) |
|
|
