(a)
(b)
(c)
(d)
Figure 5: The difference of crop yield in the East European Plain in the westward QBO phase as compared to the eastward phase: (a) spring wheat yield and (b) winter wheat yield in the period 1953–2011 and (c) spring barley yield in the period 1958–2011. The positive difference exceeding 20% is shown by dark gray color, 10–20% gray color, and less than 10% light gray color. White contour shows significant difference. The positive differences of the spring wheat yield and the winter wheat yield in the westward QBO phase as compared with eastward phase are shaded (d).