The land–sea thermal contrast is known to have a significant impact on the atmospheric circulation. We investigated the influence of the thermal contrast between the Arabian Sea (AS) and the Iranian Plateau (IP) on the interannual variability of the East Asian summer monsoon (EASM). It is found that the thermal distribution of AS–IP exhibits a fixed dipole mode. When the apparent heat over AS (IP) is higher (lower) than normal, summer rainfall is abundant over the mid- and lower reaches of the Yangtze River and Japan with the adjacent maritime regions. By contrast, there is lower rainfall in North China and the coastal regions of South China. We attribute this phenomenon to the propagation of mid-latitude Rossby waves, which play a crucial role in regulating the atmospheric circulations on East Asia and the Northwest Pacific. Significant anomalies in the transport of water vapor were seen in our statistical analyses and were partly reproduced by the Linear Baroclinic Model and Weather Research and Forecasting model experiments. The anticipated outcomes of this research will help to identify another factor related to the variability of the EASM, and provide a scientific basis for understanding the distribution and interaction of thermal anomalies on the plateau system and the Indian Ocean.

Arabian Sea,Iranian Plateau,land-sea thermal contrast,East Asian summer monsoon,interannual variability