Figure 6: (a) Difference between strong and weak HC cases for divergence at 200 hPa, (b) correlation between austral winter HCI and divergence at 200 hPa, (c) difference between strong and weak HC cases for Rossby wave source at 200 hPa, (d) correlation between austral winter HCI and the Rossby wave source at 200 hPa. The shaded areas in grey scale (see vertical bar) are statistically significant values at the 90%, 95%, and 99% levels according to a two-tailed Student’s t-test, and the contour interval is s^{−1} for (a) and s^{−2} for (c). In (b) and (d) regions exceeding 95% significance level (>) are shaded, and the contour interval is 0.2.