Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40645-018-0178-5/MediaObjects/40645_2018_178_Fig1_HTML.gif)
Factor loadings and the time coefficients of EOF1 and EOF2. The contour interval is 0.1 in a and c. The open circles in a and c indicate the observation stations used for the EOF analysis. The red cross marks in a indicate the observation stations used in Fig. 4. The thick and thin lines in b and d indicate the mean time coefficients averaged for 1951–2012 and the time coefficients in each year, respectively. The red and blue inverse triangles in b denote the first pentad (the 29th and 71st pentads) when the sign of the mean time coefficients for the EOF1 changed