Fig. 1 Distributions of 38 meteorological stations in Northeast China

Fig. 2 (a) Normalized time series of rainfall in May over Northeast China during 1961-2015 and its 11-year running mean components, as well as (b) its moving t-test

Fig. 3 Rainfall anomalies in May over Northeast China, shown as the percentage of the rainfall departure from the 1961-2015 mean. (a) the average of 2004-2015, (b) the average of 1984-1993

Fig. 4 Differences of (a) 200 hPa zonal wind, (b) 500 hPa geopotential height and (c) 850 hPa wind in May between 2004-2015 and 1984-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies; shaded areas and areas encircled by red lines in the 850 hPa wind field indicate confident meridional and zonal wind anomalies, respectively)

Fig. 5 The 850 hPa geopotential height (unit: gpm), wind vectors (unit: m/s), and relative vorticity (unit: 10-5 s-1) in May over the Northern East Asia. (a) 1961-2015, (b) 2004-2015, (c) 1984-1993

Fig. 6 The normalized time series of Northern East Asian Low index and 11-year running mean components for the period 1961-2015

Fig. 7 The anomalous vertical movement averaged over 117.5?~132.5?E in May in (a) the average of 2004-2015, and (b) the average of 1984-1993, shown as the departure from the 1961-2015 mean (The vertical speed is amplified by 100, light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident ascending and descending motion)

Fig. 8 Differences of 200 hPa (a), 500 hPa (b) and 850 hPa (c) geopotential height (unit: gpm) in May between 2004-2015 and 1983-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies)

Fig. 9 Differences of global sea surface temperature in winter (a), spring (b) and summer (c) between 2004-2015 and 1984-1993 (Light and dark shaded areas indicate the anomalies are significant at the 0.05 and 0.01 confidence level, respectively; blue and red color shaded areas indicate confident negative and positive anomalies)

Fig. 10 The correlation coefficent from preceding December to current August between the Northeast China rainfall in May and the tropical North Atlantic sea surface temperature index and the high-latitude North Atlantic sea surface temperature index, respectively

Fig. 11 The normalized time series of the tropical North Atlantic sea surface temperature index and 11-year running mean components for the period 1961-2015

Fig. 12 Composition of the 850 hPa geopotential height and wind vectors in May over the Northern East Asia in anomalous positive (a) and negative (b) years of the tropical North Atlantic sea surface temperature index