Fig. 3: Atmospheric variance associated with the Southern Indian Ocean Dipole.
From: Southern Indian Ocean Dipole as a trigger for Central Pacific El Niño since the 2000s
Regression maps of (a) precipitation (mm day−1) and (b) 925hPa wind (vector, m s−1) and streamfunction (contours at intervals of 0.3·10−5 m2 s−1) anomalies during boreal late fall (OND) season with respect to the normalized OND Southern Indian Ocean Dipole (SIOD) index for 1998−2019. The shading and vector in a, and b denote the region where the statistical significance is above the 95% confidence level. c Regression of 925 hPa zonal wind anomalies averaged over 5° S–5° N over the Pacific during the following boreal spring (MAM) season with respect to the normalized OND SIOD index for 1998−2019 (blue line). The red line is the same but for the partial regression after excluding the impact of the boreal winter (DJF) Niño4 index. d Partial lag-regression of 925 hPa zonal wind anomalies averaged over 120°–150° E, 5° S– 5° N over the equatorial western Pacific from the OND season to the subsequent year’s boreal early winter (NDJ) season with respect to the normalized OND SIOD index after excluding the impact of the DJF Niño4 index for 1998−2019 (blue line). The red line is the same but for the partial lag-regression with respect to the normalized DJF Niño4 index after excluding the impact of the OND SIOD index for 1998−2019. The open circles in c, and d indicate correlation coefficients that are statistically significant at the 95% confidence level.
