The relationship between spring soil moisture and summer hot extremes over North China

The increase in the occurrence of hot extremes is known to have resulted in serious consequences for human society and ecosystems. However, our ability to seasonally predict hot extremes remains poor, largely due to our limited understanding of slowly evolving earth system components such as soil moisture, and their interactions with climate. In this study, we focus on North China, and investigate the relationship of the spring soil moisture condition to summer hot extremes using soil moisture data from the Global Land Data Assimilation System and observational temperature for the period 1981-2008. It is found that local soil moisture condition in spring is closely linked to summer hot days and heat waves over North China, accounting for 19%-34% of the total variances. Spring soil moisture anomalies can persist to the summer season, and subsequently alter latent and sensible heat fluxes, thus having significant effects on summer hot extremes. Our findings indicate that the spring soil moisture condition can be a useful predictor for summer hot days and heat waves over North China.