Poster

IAMAS

JMP03 - High-impact Weather and Climate Extremes

Regional Influences on the Temporal Evolution of the 2020 East Asian Monsoon: A Replay Experiment Analysis

In 2020, the East Asian monsoon exhibited record-breaking precipitation, leading to significant property damage and loss of life in Korea, China, and Japan. As a result, numerous studies have investigated the extreme rainfall mechanisms of this monsoon season. Previous research has identified various contributing factors, including anomalous warming in the Indian Ocean, reduced Arctic sea ice extent, and increased soil moisture in the Indochina Peninsula. However, a quantitative comparison of the relative influences of these factors has not yet been thoroughly conducted. Additionally, studies have explored how precipitation patterns changed over time during the monsoon season. The 2020 monsoon was particularly prolonged compared to other years, largely due to a Eurasian blocking pattern that prevented the northward migration of the monsoon front in its later stages. Identifying the causes of these temporal variations in atmospheric conditions is crucial for understanding extreme monsoon rainfall. In this study, we quantitatively analyze the regional influences on different phases of the 2020 East Asian summer monsoon using an atmosphere-ocean-land coupled model (GloSea6). To achieve this, we employ a regional replay system for climate model experiments. This method updates incremental tendencies between the model's background state and analysis fields on a region- and variable-specific basis. Unlike nudging, which directly modifies model states, the replay method updates only the tendencies, thereby preserving the model's inherent dynamics. By comparing regional replay experiments, we aim to quantify the impact of regional environmental factors on different monsoon phases, providing deeper insights into the mechanisms driving extreme monsoon rainfall.