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Ann. Geophys., 20, 661-677, 2002
www.ann-geophys.net/20/661/2002/
© European Geosciences Union 2002
Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70° N, modelled tides (GSWM, CMAM)
A. H. Manson1, C. Meek1, M. Hagan2, J. Koshyk3, S. Franke4, D. Fritts5, C. Hall6, W. Hocking7, K. Igarashi8, J. MacDougall7, D. Riggin5, and R. Vincent9
1Institute of Space and Atmospheric Studies, University of Saskatchewan, Canada
2NCAR, Boulder NCAR, Boulder, USA
3Department of Physics, University of Toronto, Canada
4Space Science and Remote Sensing Laboratory, University of Illinois, USA
5Colorado Research Associates (a Division of Northwest Research Associates), Boulder, USA
6Auroral Observatory, University of Tromsø, Norway
7Department of Physics and Astronomy, University of Western Ontario, Canada
8Communications Research Laboratory, Tokyo, Japan
9Department of Physics and Mathematical Physics, University of Adelaide, Australia
Correspondence to: A. H. Manson
(manson@dansas.usask.ca)
Abstract. In an earlier paper
(Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency
Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original
1995 version). The radars are located between the equator and high northern
latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London
(43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was
applied, to ensure consistency of amplitudes and phases in the 75–95 km
height range. For the diurnal tide, seasonal agreements between observations
and model were excellent while for the semi-diurnal tide the seasonal
transitions between clear solstitial states were less well captured by the
model.
Here the data set is increased by the addition of two
locations in the Pacific-North American sector: Yamagawa 31° N, and Wakkanai
45° N. The GSWM model has undergone two additional developments (1998, 2000)
to include an improved gravity wave (GW) stress parameterization, background
winds from UARS systems and monthly tidal forcing for better characterization
of seasonal change. The other model, the Canadian Middle Atmosphere Model (CMAM)
which is a General Circulation Model, provides internally generated forcing
(due to ozone and water vapour) for the tides.
The two GSWM versions show distinct differences, with the
2000 version being either closer to, or further away from, the observations
than the original 1995 version. CMAM provides results dependent upon the GW
parameterization scheme inserted, but one of the schemes provides very useful
tides, especially for the semi-diurnal component.
Key words. Meteorology and
atmospheric dynamics (middle atmosphere dynamics; waves and tides)
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