Fig. 3: The time series and probability density function (PDF) distribution of TXx7 anomalies and corresponding eddy geopotential height anomalies.

Here, TXx7 is defined as the annual summer (June-August) maxima of the 7-day running mean of the daily maximum temperature anomaly area-weighted averaged over Western North America (WNA). a The anomalies of annual summer TXx7 (red solid line, unit:  °C) and corresponding eddy geopotential height anomalies (blue solid line, unit: gpm) at 500 hPa area-weighted averaged over the WNA during 1959–2021 for ERA5 reanalysis. The orange line denotes the summer mean 2 m mean temperature anomaly area-weighted averaged over the WNA. The dotted line denotes the trend of TXx7 anomalies and corresponding eddy geopotential height anomalies. b is the same as a but for the CESM1 historical and RCP8.5 simulations during 1959–2100. The gray shadows denote the near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100). Solid lines represent the results of the ensemble mean; the light shades are for the 5th percentile to 95th percentile for the 40-member. c The PDF distribution of TXx7 anomalies during 1991–2020 for ERA5 reanalysis (black curve), during 1991–2020 for 40-member realization in CESM1 historical simulation (orange curve), for 1620 years of preindustrial control simulation (blue curve), for RCP8.5 simulation in the near-term (yellow curve), mid-term (red curve) and long-term (dark red curve). The black vertical line indicates the TXx7 anomalies of 2021 from ERA5. d is the same as c but for the PDF distribution of eddy geopotential height anomalies corresponding to TXx7. The black vertical line indicates the eddy geopotential height anomalies of the average of 27 June–3 July 2021 from ERA5.