Effect of tropical Indian Ocean thermal condition during preceding winter on summer high temperature anomalies over the southern Yangtze River valley

The present study investigates signals of summer high temperature anomalies over the southern Yangtze River valley (SYRV) region. The results show that summer high temperature anomalies over the SYRV region are associated with preceding winter sea surface temperature (SST) and surface air temperature (SAT) anomalies over the tropical Indian Ocean (TIO), particularly the tropical northwestern (5 degrees-15 degrees N, 55 degrees-75 degrees E) and southwestern (15 degrees S-0 degrees N, 40 degrees-55 degrees E) Indian Ocean regions. Coupled with SST, positive SAT anomalies over the TIO regionmay persist from preceding winter to summer, leading to more summer precipitation over the northwestern India and Arabian Sea (IAS) region. More summer precipitation (increased condensational heating) over the IAS region can regulate the strength and location of the western Pacific subtropical high and the South Asian high and result in their vertical superposition over the SYRV region. As such, a deep and stable high-pressure anomaly forms over the SYRV region and results in high temperature anomalies. In this process, anomalous precipitation over the IAS region may to some degree act as a 'bridge' in providing a delayed impact of the preceding winter TIO SAT on summer SAT over the SYRV region. The effect of the preceding winter TIO SAT on summer SYRV SAT becomes weaker after removing the variability of IAS precipitation.