Details

Autor(en) / Beteiligte

• Ren, Qiaoling
• Liu, Fei
• Wang, Bin
• Yang, Song
• Wang, Hui
• Dong, Wenjie

Titel

Origins of the Intraseasonal Variability of East Asian Summer Precipitation

Ist Teil von

• Geophysical research letters, 2022-02, Vol.49 (4), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2022

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Accurate subseasonal prediction of East Asian summer precipitation (EASP) requires a deep understanding of the origins of its intraseasonal variability (ISV). However, the relative contributions to the EASP ISV from local processes, tropical intraseasonal oscillation (ISO), and extratropical influence remain unknown. We conducted a set of numerical experiments with a grid nudging method to confirm the roles of external forcing from mid‐to‐high latitude wave trains and tropical ISO and quantify their relative contributions. The Community Earth System Model can reproduce realistic EASP ISV and associated preceding signals. The tropical and mid‐to‐high latitude forcings account for, respectively, 53% and 40% of the total variance for the two leading ISV modes of EASP. The tropical forcing contributes more significantly to the two leading modes (31% and 40%, respectively) compared to the extratropical forcing (24% and 15%). These external forcings mainly affect EASP regional averages rather than the values of local (grid) scale. Plain Language Summary East Asian summer monsoon precipitation exhibits significant fluctuations on a 2–5‐week time scale beyond the synoptic scale. These fluctuations are called intraseasonal variability (ISV). Since East Asia is located in between the largest continent (Eurasia) and the largest ocean (the Pacific), its ISV is affected by the southeastward propagating high‐latitude disturbances (wave trains) and northwestward propagating tropical ISV. However, the relative roles of these outside influences have never been quantified. We applied a climate model that could reproduce realistic ISV and designed a suite of numerical experiments to quantitatively determine the contributions of these “external forcings” to the East Asian ISV. About one half of the total intraseasonal variance (a measure of ISV intensity) arises from the mid‐to‐high latitude and tropical forcings. Thus, accurate simulations of tropical ISV and mid‐to‐high latitude wave trains are critical for improving subseasonal prediction over East Asia. Key Points Community Earth System Model performs well in simulating the leading intraseasonal variability (ISV) modes of East Asian summer precipitation (EASP) and their preceding tropical and mid‐to‐high latitude signals Tropical and mid‐to‐high latitude forcings together contribute half of the total variance of the two leading ISV modes of EASP External tropical and mid‐to‐high latitude forcings affect EASP ISV more apparently on a regional, rather than a local, spatial scale