Fig. 4

Histograms showing the distributions of a elongation azimuth, b length, and c migration speed of Es patches with frontal structures observed in 2010. They are typically elongated in E-W with the median length of ~100 km b. In c, N-S components of the migration velocities are shown. They are distributed in the range of 30–100 m/s with the average of 60 m/s