Fig. 4

Daily time series of the indices of the blocking high over eastern Siberia (pink), Okhotsk high (OH; red), Korean trough (yellow), northwestern Pacific subtropical high (NWPSH; blue), convective activity over the eastern Indian Ocean (green), and precipitation in Japan (heavy blue bar) in August 2021. Dotted and solid lines indicate the daily and 5-day running means, respectively. The bottom bars also indicate the 5-day running mean. Vertical dotted lines denote August 13, 2021. The indices were defined by area average as follows; Blocking high: Geopotential height anomaly at 500 hPa (unit: m) over eastern Siberia [50°–60°N, 125°–140°E], OH: SLP anomaly (unit: hPa) over the Okhotsk Sea [45°–60°N, 140°–155°E], Korean trough: Geopotential height anomaly at 500 hPa (unit: m) over the Korean Peninsula [30°–45°N, 120°–135°E], NWPSH: SLP anomaly (unit: hPa) over the subtropical northwestern Pacific [15°–30°N, 130°–155°E], Convective activity: Precipitation anomaly (unit: mm day⁻¹) over the eastern Indian Ocean [5°S–10°N, 85°–100°E], Japan precipitation: Precipitation (unit: mm day⁻¹) over Japan [30°–37°N, 127°–142°E]. Precipitation was based on the GPCP data