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| Titel |
Studies of vertical fluxes of horizontal momentum in the lower atmosphere using the MU-radar |
| VerfasserIn |
F. S. Kuo, H. Y. Lue, C. L. Fern, J. Röttger, S. Fukao, M. Yamamoto |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 26, no. 12 ; Nr. 26, no. 12 (2008-11-26), S.3765-3781 |
| Datensatznummer |
250016308
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3765-2008.pdf |
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| Zusammenfassung |
| We study the momentum flux of the atmospheric motions in the height ranges
between 6 and 22 km observed using the MU radar at Shigaraki in Japan during
a 3 day period in January 1988. The data were divided by double Fourier
transformation into data set of waves with downward- phase- velocity and
data set of waves with upward-phase-velocity for independent momentum flux
calculation. The result showed that both the 72 h averaged upward flux
and downward flux of zonal momentum were negative at nearly each height,
meaning that the upward flux was dominated by westward propagating waves
while the downward flux was dominated by eastward propagating waves. The
magnitude of the downward flux was approximately a factor of 1.5 larger than
the upward flux for waves in the 2~7 h and 7~24 h period
bands, and about equal to the upward flux in the 10–30 min and 30 min–2 h
period bands. It is also observed that the vertical flux of zonal momentum
tended to be small in each frequency band at the altitudes below the jet
maximum (10~12 km), and the flux increased toward more negative
values to reach a negative maximum at some altitude well above the jet
maximum. Daily averaged flux showed tremendous variation: The 1st 24 h (quiet day)
was relatively quiet, and the fluxes of the 2nd and
3rd 24 h (active days) increased sharply. Moreover, the upward
fluxes of zonal momentum below 17 km in the quiet day for each period band
(10~30 min, 30 min~2 h, 2~7 h, and 7~24 h)
were dominantly positive, while the corresponding downward fluxes were
dominantly negative, meaning that the zonal momentum below 17 km in each
period band under study were dominantly eastward (propagating along the mean
wind). In the active days, both the upward fluxes and downward fluxes in
each frequency band were dominantly negative throughout the whole altitude
range 6.1–18.95 km. |
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