Potential Impacts of the North Atlantic Horseshoe Pattern on China Compound Heat-Humidity Extremes

Abstract

Compound heat-humidity extremes (CHHEs) have gained significant attention as crucial indicators of heat stress. This research investigates the summer wet bulb globe temperature (WBGT) to elucidate the spatial variation of CHHEs across China from 1961 to 2022. The results reveal a clear increase in CHHEs, with the highest WBGT observed in southeastern China, while significant increases are noted in the northwestern and northeastern regions. Empirical orthogonal function analysis identifies three leading patterns: a consistent spatial increase, a north (decreasing)–south (increasing) dipole, and a west (decreasing)–east (increasing) dipole. Both observations and model simulations indicate that the North Atlantic Horseshoe (NAH) sea surface temperature (SST) anomaly pattern is a reliable predictor for CHHEs in China via influencing the North Atlantic Oscillation (NAO) and modulating large-scale circulations. This combined with the westward extension of the Western North Pacific Anomalous Anticyclone (WNPAC), leads to a consistent rise in CHHEs, particularly in Central China. Regarding the north–south dipole, air-sea interactions driven by the NAH reinforce the negative phase of the Eurasian (EU) teleconnection pattern through the NAO, intensifying cyclonic and anticyclonic anomalies over Mongolia to northern China and southern China, respectively. Furthermore, the NAH pattern during May–July effectively predicts summer CHHEs north–south dipole variations using the genetic algorithm-based evolving neural network. This research offers valuable insights for predicting CHHEs in China from the perspective of North Atlantic SST anomalies.