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| Titel |
Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data |
| VerfasserIn |
R. Wang, S. D. Zhang, H. G. Yang, K. M. Huang |
| 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 ; 30, no. 10 ; Nr. 30, no. 10 (2012-10-04), S.1463-1477 |
| Datensatznummer |
250017276
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1463-2012.pdf |
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| Zusammenfassung |
| The activities of mid-latitude planetary waves (PWs) in
the troposphere and lower stratosphere (TLS) are presented by using the
radiosonde data from 2000 to 2004 over four American stations (Miramar Nas,
32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth,
32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W) and one
Chinese station (Wuhan, 30.5° N, 114.4° E). Statistically, strong PWs
mainly appear around subtropical jet stream in the troposphere and lower
stratosphere. In the troposphere, the activities of the mid-latitude PWs are
strong around the centre of the subtropical jet stream in winter and become
small near the tropopause, which indicates that the subtropical jet stream may
strengthen the propagation of PWs or even be one of the PW excitation
sources. Among the three disturbance components of temperature, zonal and
meridional winds, PWs at Wuhan are stronger in the temperature component, but
weaker in the zonal wind component than at the other four American stations.
While in the meridional wind component, the strengths of PW spectral
amplitudes at the four American stations decrease from west to east, and
their amplitudes are all larger than that of Wuhan. However, the PWs are
much weaker in the stratosphere and only the lower frequency parts remain.
The amplitudes of the PWs in the stratosphere increase with height and are
strong in winter with the zonal wind component being the strongest. Using
the refractive index, we found that whether the PWs could propagate upward
to the stratosphere depends on the thickness of the tropopause reflection
layer. In the case study of the 2000/2001 winter, it is observed that the
quasi 16-day wave in the troposphere is a quasi standing wave in the
vertical direction and propagates upward slowly with vertical wavelength
greater than 24 km in the meridional component. It propagates eastward with
the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is
probably the same quasi 16-day wave at the three American stations (Miramar
Nas, Santa Teresa and Fort Worth), which propagates steadily along the
latitude. The quasi 16-day wave in the stratosphere is also a standing wave
with vertical wavelength larger than 10 km in the zonal wind component, and
it is westward with the zonal number 1–2. However, the quasi 16-day wave in
the stratosphere may not come from the troposphere because of the different
concurrent times, propagation directions and velocities. By using
the global dataset of NCEP/NCAR reanalysis data, the zonal propagation
parameters of 16-day waves in the troposphere and stratosphere are
calculated. It is found that the tropospheric 16-day wave propagates
eastward with the zonal number 6, while the stratospheric 16-day wave
propagates westward with the zonal number 2, which matches well with the
results of radiosonde data. |
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