Delayed Impacts of ENSO on the Frequency of Summer Extreme Hot Days in the Asian Monsoon Region. Part I: Observation, Historical Simulation, and Future Projection in CMIP6 Models

• DOI: 10.1175/jcli-d-21-0667.1
• Publication Date: 2023-01-18T14:57:49Z
• Authors: Jiaxin Ye; Chaoxia Yuan; Mengzhou Yang; Xinyu Lu; Jing-Jia Luo; Toshio Yamagata
• Keywords: Teleconnection; Anomaly (physics); Anticyclone; Geopotential height; Hindcast; Atmospheric Circulation; Walker circulation; Multivariate ENSO index

Abstract Significant anomalies in frequency of summer extreme hot days (SEHDs) are broadly observed the Asian monsoon region (AMR) post-ENSO summers. The delayed ENSO impacts mainly conveyed by provoking Indo-western Pacific Ocean capacitor (IPOC) effect that maintains anomalous anticyclone western North Pacific. related diabatic heating anomaly can trigger westward-propagating Rossby wave to Indian subcontinent, which increases geopotential heights, reduces cloud cover, and thus seasonal surface temperature SEHD southern AMR. Besides, reduced atmospheric moisture hinders northward propagation intraseasonal oscillation (ISO) modulates occurrence individual ISO phases, contributing significantly increased/decreased SEHDs eastern China/Hokkaido, Japan, post–El Niño 25-model-ensemble mean CMIP6 historical runs reproduce well AMR summers due realistic simulation on temperature, although a large intermodel spread exists different strengths IPOC each model owing biases state tropical Pacific, variance, teleconnection Ocean. Furthermore, future projections under SSP5-8.5 scenario show remain stable global warming via similar mechanism as observations runs.