Spring soil temperature as a predictor of summer heatwaves over northwestern China

Abstract

Northwestern China has been increasingly affected by summer heatwaves in recent decades. In this study, we show that summer heatwave events over northwestern China are significantly correlated with the spring soil temperature over central Asia for the period of 1979–2017, irrespective of whether the data are detrended. By analyzing the physical links, we find that warmer spring soil temperature over central Asia tends to result in positive geopotential height anomalies over northern China and Mongolia including northwestern China in summer, which may subsequently lead to more heatwave events via the effects on downward solar radiation, subsidence warming and other processes. We further establish a statistical model to predict summer heatwaves over northwestern China based on the spring soil temperature over central Asia. The results show that the leave-one-out cross-validation for the correlation skill is 0.56 for the period of 1979–2017. The spatial patterns are captured well in the hindcast experiments for the period of 2012–2017, with all pattern correlation coefficients ≥0.88. Our proposed prediction model can be applied to practical forecasting and may help to reduce the damage caused by summer heatwaves over northwestern China.