Fig. 6: Background conditions of summer North American blocking events in 2023 and the PDO- & EP El Niño.
From: Atmospheric and oceanic drivers behind the 2023 Canadian wildfires
a–c Summer (May to July, MJJ) mean 500 hPa zonal wind (U500, unit: m s−1) and (d–f) non-dimensional meridional potential vorticity gradient (PVy, unit: non-dimensional) anomalies for North American blocking events excluded (the days of blocking events from lag −10 to 10 days are removed, where lag 0 denotes the strongest day of the blocking event) for (a, d) 2023 and (b, e) PDO− & EP El Niño and (c, f) their difference (a minus b and d minus e). The color shading represents the area being statistically significant at the 95% confidence level.
