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5. Summary

By analyzing operational high-resolution radiosonde data in Japan over 4 years, it is revealed that long-lasting layered wind disturbances appear frequently in winter at several stations simultaneously. The dominant height region is 8-16km. The result of an EOF analysis indicates that there are two dominant modes for their appearance. The first component (EOF1) is dominant in the middle of Japan (30-37N), and the second (EOF2) dominant in the south of Japan (23-30N). The background fields for the layered disturbances are examined using NCEP reanalysis data. The background potential vorticity is frequently negative when and where EOF2 disturbances are dominant, suggesting that the EOF2 disturbances are due to inertial instability. The negative potential vorticity air for EOF2 disturbances can be traced back to the equatorial region within a few days. On the other hand, the background potential vorticity around EOF1 disturbances is low but scarcely negative. Air parcels at EOF1 stations are traced back to far west because of the existence of strong eastward jet stream. Thus, it is inferred that the EOF1 disturbances are due to inertia-gravity waves trapped in a duct of the westerly jet core.

Previous: Backward trajectory analysis Up: Ext. Abst.