Figure 4

Regression of DJF equatorially averaged (10°S-10°N) JRA temperatures (shading), and zonal and vertical winds (vectors; scale in lower right panel) onto the JRA RMM1 + RMM2 time series for QBOE (left column) and QBOW (right column). Below each panel is the regression of JRA OLR onto the JRA RMM1 + RMM2 index. The top row is for the period 1959–1979 and the bottom row is 1980–2014. The mean temperature anomaly for QBOE and QBOW for each period relative to the climatology for 1980–2010 is contoured (contour interval 0.1°K). The vector scale indicates a 10 ms⁻¹ zonal wind or 7.41 × 10⁻³ Pa s⁻¹ vertical velocity anomaly. The vertical velocity has been multiplied by −1 so that an upward arrow indicates upward motion. Orange dots highlight areas where the difference between QBOE and QBOW is statistically significant at the 5% level using a one-tailed Student’s t-test.