Fig. 7: Linear trend patterns of summer zonal wind and meridional potential vorticity gradient anomalies over 1979–2003 and 2004–2021.
From: Rapid summer Russian Arctic sea-ice loss enhances the risk of recent Eastern Siberian wildfires
a–d Linear trend patterns of summer (June–August, JJA) mean 500-hPa (a, b) zonal wind (U500) (color shading; unit: m/s per decade) and c, d non-dimensional meridional potential vorticity gradient (PVy) anomalies (color shading; unit: non-dimensional value per decade) without Siberian blocking (SB) events (i.e., blocking days from lag\(\,-\,10\) to 10 days are removed for each SB event and lag 0 denotes the peak day of SB) over (a, c) 1979–2003 and b, d 2004–2021. The dotted regions represent that the linear trends are statistically significant (p < 0.05) for a two-sided student t-test.
