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AGU: Journal of Geophysical Research, Space Physics

 

Index Terms

  • Meteorology and Atmospheric Dynamics: Waves and tides
  • Meteorology and Atmospheric Dynamics: Thermospheric dynamics
  • Atmospheric Composition and Structure: Instruments and techniques
  • Meteorology and Atmospheric Dynamics: Instruments and techniques
Abstract
Cited By (6)
 

Abstract

Longitude variability of the solar semidiurnal tide in the lower thermosphere through assimilation of ground- and space-based wind measurements

K. M. Cierpik

Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, USA

J. M. Forbes

Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, USA

S. Miyahara

Department of Earth and Planetary Science, Kyushu University, Fukuoka, Japan

Y. Miyoshi

Department of Earth and Planetary Science, Kyushu University, Fukuoka, Japan

A. Fahrutdinova

Radiophysics Department, Kazan University, Kazan, Russia

C. Jacobi

Institute for Meteorology, University of Leipzig, Leipzig, Germany

A. Manson

Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada

C. Meek

Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada

N. J. Mitchell

Department of Electronic and Electrical Engineering, University of Bath, Bath, UK

Y. Portnyagin

Institute for Experimental Meteorology, Obninsk, Russia

Wind measurements from the Upper Atmosphere Research Satellite (UARS) and model output from the Middle Atmosphere General Circulation Model (GCM) at Kyushu University are used to investigate the nature of nonmigrating semidiurnal tides between 50–55°N using combined space-based (SBM) and ground-based (GBM) wind measurements at 95 km. The GCM is used to create a mock database to test the effects of various sampling scenarios, data gaps, and relative weighting between SBM and GBM, on retrieval of the longitude structure of the semidiurnal tide. SB sampling is based upon orbital characteristics of UARS. GB sampling corresponds to hourly radar measurements from Saskatoon (52°N, 107°W), Sheffield (53°N, 4°W), Collm (52°N, 15°E), Obninsk (55°N, 37°E), and Kazan (56°N, 49°E). Results are presented for the month of August when semidiurnal amplitudes are large and sampling by UARS instruments is good. By compositing over a 5–10 day “fit span,” it is found that the combination of temporal coverage by GB radars and spatial sampling by the satellite is sufficient to allow reasonable recovery of the zonal wave number s = 1, 2, 3 components of the semidiurnal tide. Over significantly longer fit spans, the contributions of GBM become less critical. Using actual UARS and GBM during 1–20 August 1993, the semidiurnal amplitude of eastward wind is found to vary from a minimum value (12 ms−1) at 20°E, to a maximum of 45 ms−1 near 160°E, and a secondary maximum (29 ms−1) at 300°E. The zonal wave number components corresponding to this longitude variation in the semidiurnal tide are 7.7 ± 1.9 ms−1, 19.8 ± 1.5 ms−1 and 13.0 ± 1.3 ms−1 for s = 1, 2, 3 (westward), respectively where ±1−σ uncertainties are indicated. These results are in reasonable agreement with those simulated within the Kyushu GCM. However, there is roughly a four- to five-hour phase offset between the phases recovered from the observational data and from the Kyushu GCM, possibly connected with strong model phase gradients in this atmospheric regime.

Received 25 February 2002; accepted 10 January 2003; published 21 May 2003.

Citation: Cierpik, K. M., J. M. Forbes, S. Miyahara, Y. Miyoshi, A. Fahrutdinova, C. Jacobi, A. Manson, C. Meek, N. J. Mitchell, and Y. Portnyagin (2003), Longitude variability of the solar semidiurnal tide in the lower thermosphere through assimilation of ground- and space-based wind measurements, J. Geophys. Res., 108(A5), 1202, doi:10.1029/2002JA009349.

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