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4. EOF and SVD analysis of the troposphere

In order to confirm the dynamical coupling between the troposphere and stratosphere in more detail, we applied the EOF and SVD analysis to the tropospheric zonal winds and 300hPa heat fluxes.

Fig.4a shows the first mode of tropospheric U (TUEOF1, Fraction of variance 55%), which is the dipole pattern throughout the whole troposphere, indicating the appearance of single and double jet structure. The classification by this principal component TUPC1 sign (Fig.4b) confirms the separation of the east-west drift of the phase of stratospheric waves.

On the other hand, the first component of 300hPa T'v' pattern (VTEOF1, Fig.5a) reflects the wave activity over the Indian Ocean, though the fraction of variance is rather weak (9.3%), and the stratospheric wave intensity is clearly separated by the sign of TVPC1 (Fig.5b).

Figure 4 . Latitude height section (1000-100 hPa) of the first EOF mode for monthly mean zonal wind averaged longitudinally for the eastern hemisphere, (b) Scatter diagram of the value and the longitude of the minimum Z* (trough) at 10hPa.
Red (blue) circle denotes the positive (negative) PC1 index for zonal wind U .



Figure 5 . Same as Fig.4 ,but (a) the first EOF mode for monthly mean horizontal eddy heat flux at 300 hPa , (b) green (orange) circle denotes the positive (negative) PC1 index for T'v' .


Furthermore, the result of the SVD analysis for the 10hPa height field anomaly Z* and 300hPa T'v', though not shown here, shows that the first and second mode explain the fluctuation of the phase and amplitude for Z* respectively. The temporal correlation coefficients between the expansion coefficients is high for the first two mode.(r=0.78,0.77 ,respectively). This also confirms the dynamical control of planetary waves in the stratosphere by the tropospheric transient disturbances.