Impacts of 10–30-day atmospheric oscillation on persistent compound heatwaves in the Yangtze River Delta with implications for local electricity demand and supply

Abstract

The Yangtze River Delta (YRD) is a hotspot of compound heatwaves characterized by scorching day and sweltering night persisting for more than 3 days. The YRD compound heatwaves are intimately associated with the 10–30-day variations of air temperature, with 46 identified heatwaves during the summers of 1979–2022 mostly occurring within the positive phases of 10–30-day T_max and T_min anomalies. The coincidence of positive phases in 10–30-day T_max and T_min comes from a dipole pattern of the corresponding potential vorticity (PV) anomalies in the upper troposphere. This dipole PV pattern leads to anomalous descents in the YRD and associated anticyclones in the lower troposphere. As a result, the increased adiabatic heating and incident solar radiation cause the extreme daytime heat. The enhanced humidity in the YRD increases the downward longwave radiation, resulting in the extreme nighttime temperatures. As the increased temperature and humidity enhance stratification stability in the lower troposphere, the coupling between daytime and nighttime heat extremes persists, leading to a compound heatwave. During a YRD compound heatwave, the 10–30-day atmospheric intraseasonal oscillation (ISO) exerts a potential influence on the electricity demand and supply. Continuous extreme heat leads to a dramatic surge in cooling demand. While the influence of 10–30-day ISO on wind energy resources is weak, the dipole pattern of 10–30-day PV anomalies strongly reduces solar energy resources over the mid–lower reaches of the Yellow River, thus exerting greater challenges for electricity supply to the YRD.