The Influence of Heat Stress on Maize Yield and Its Association with Atmospheric General Circulation and Sea Surface Temperature

Heat stress has posed a major threat to maize growth. In this paper, the authors analyze the impact of summer extreme high temperature on maize yield at provincial scales in China. Results show that in 18 provinces, the maize yield would decrease dramatically from-1.56% to-15.06% for each standard deviation increase in extreme high temperature days, especially in Northeast China and North China. Further analysis indicates that extreme high temperature days in both Northeast China and North China appeared to increase abruptly in the middle to late 1990s. For Northeast China and North China, when the geopotential height anomaly at 500 hPa is positive, the weather is clear, which is conductive to the increase in solar radiation and favorable for the occurrence of high temperature. Looking at wind fields in the lower levels, westerly winds often prevail in Northeast China especially in Heilongjiang Province. Strong zonal circulations can block the invasion of cold air mass from high latitudes. For North China, warm temperature advection by southerly winds is dominant, which is favorable for the formation of extreme high temperature. The key oceanic region that has significant impacts on extreme high temperature in Northeast China is the Kuroshio region, while the main oceanic region affecting North China is the equatorial eastern Pacific. Positive anomalies in this region would lead to eastward shift of the western Pacific subtropical high. With insufficient supply of water vapor and strong downdrafts, North China is prone to high temperature weather.