|
|
 |
|
|
Ann. Geophys., 20, 691-709, 2002
www.ann-geophys.net/20/691/2002/
© European Geosciences Union 2002
The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results
Y. Luo1,*, A. H. Manson1, C. E. Meek1, C. K. Meyer2, M. D. Burrage3,**, D. C. Fritts2, C. M. Hall4, W. K. Hocking5, J. MacDougall5, D. M. Riggin2, and R. A. Vincent6
1Institute of Space and Atmospheric Studies, University of Saskatchewan, Canada
2Colorado Research Associates, Boulder, USA
3Space Physics Research Laboratory, University of Michigan, Ann Arbor, USA
4Tromsø Geophysical Observatory, University of Tromsø, Norway
5Department of Physics and Astronomy, University of Western Ontario, Canada
6Department of Physics and Mathematical Physics, University of Adelaide, Australia
*now at: Canada Centre for Remote Sensing, Ottawa, Canada
**M. Burrage died tragically on 10 October 1999, and we dedicate this paper to his memory.
Correspondence to: Y. Luo (Yi.Luo@ccrs.nrcan.gc.ca)
Abstract. The mesospheric and lower
thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located
from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N,
107° W), London (43° N, 81° W), Hawaii (21° N, 157° W) and Christmas
Island (2° N, 157° W), respectively, are used to study the planetary-scale
16-day waves. Based on the simultaneous observations (1993/1994), the
variabilities of the wave amplitudes, periods and phases are derived. At mid-
and high-latitude locations the 16-day waves are usually pervasive in the
winter-centred seasons (October through March), with the amplitude gradually
decreasing with height. From the subtropical location to the equator, the
summer wave activities become strong at some particular altitude where the
inter-hemisphere wave ducts possibly allow for the leakage of the wave from the
other hemispheric winter. The observational results are in good agreement with
the theoretical conclusion that, for slowly westward-traveling waves, such as
the 16-day wave, vertical propagation is permitted only in an eastward
background flow of moderate speed which is present in the winter hemisphere.
The wave period also varies with height and time in a range of about 12–24
days. The wave latitudinal differences and the vertical structures are compared
with the Global Scale Wave Model (GSWM) for the winter situation. Although
their amplitude variations and profiles have a similar tendency, the
discrepancies are considerable. For example, the maximum zonal amplitude occurs
around 40° N for radar but 30° N for the model. The phase differences between
sites due to the latitudinal effect are basically consistent with the model
prediction of equatorward phase-propagation. The global 16-day waves at 95 km
from the HRDI wind measurements during 1992 through 1995 are also displayed.
Again, the wave is a winter dominant phenomenon with strong amplitude around
the 40–60° latitude-band on both hemispheres.
Key words. Meteorology and
atmospheric dynamics – waves and tides – middle atmosphere dynamics –
thermospheric dynamics
Full Article in PDF (8149 KB) |
|
|
