Characteristics of internal variability on summer rainfall in Northeast Asia in a changing climate

Abstract

Using a 35-ensemble member simulated with the community earth system model-large ensemble (CESM-LE) experiment, we examined the characteristics of internal variability (IV) on the Northeast Asian summer rainfall anomaly (NASRA) in a changing climate. The NASRA, which is defined as the rainfall anomaly averaged across Northeast Asia (30 degrees-40 degrees N, 115 degrees-145 degrees E), consists of the tropics-related rainfall anomaly and the extratropics-related rainfall anomaly. In this study, the IV was estimated by the spread of rainfall simulated in each ensemble member from their ensemble mean. The IV associated with the tropics-related rainfall variability did not change significantly from the present climate to a future climate. In contrast, the IV associated with the NASRA gradually increased from the mid-twenty first century and this was mostly due to an increase of IV associated with the extratropics-related rainfall variability. This implies that the predictability of NASRA may decrease in a future changing climate because of the extratropics-related rainfall variability associated with zonal atmospheric wave train patterns including Eurasian-like pattern, Silk Road pattern or Circumglobal Teleconnection pattern. We also discussed the characteristic change of IV associated with the tropics-related and the extratropics-related rainfall variability in a future warmer climate.