- 1Graduate Institute of Sustainability Management and Environmental Education, National Taiwan Normal University, Taipei, Taiwan (khelin@ntnu.edu.tw)
- 2National Taiwan University, Taipei, Taiwan
- 3Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan
The East Asian summer monsoon (EASM) is a distinctive component of the Asian climate system, strongly influenced by orographic forcing. Unlike Indian summer monsoon which occurs within South Asian summer monsoon (SASM) trough and presents a relative uniformity of rainfall distribution allowing for an All Indian Rainfall index to measure its variability, the definition of the EASM intensity is more complex. One of the main reasons is the vast spatial extent of the EASM encompassing tropics, subtropics and midlatitudes, making it difficult to attribute its variability. Despite the challenges, studying the evolution of the South and East Asian monsoon systems over centennial to millennial timescales is essential for developing a comprehensive understanding of both high- and low-frequency variations in monsoon behavior and their relationship with general atmospheric circulations. Many previous studies used geochemical proxy records from oceanic sediments or continental archives to reconstruct paleomonsoon indices. However, most reconstructions relied on rainfall information extracted from individual sites, facing limited spatial coverage and constrained ability to generalize findings across broader monsoon systems.
In this study, we present a novel approach to reconstruct paleo SASM and EASM indices. First, we applied the present method for estimating SASM and EASM indices (Wang et al. 2008) to calculate wind fields (zonal and meridional winds at 850hPA) from 1950 to 2020 using ERA5 data and rainfall data from NOAA Precipitation Reconstruction over Land. This approach was used to construct modern indices and investigate the relationships between rainfall and circulation anomalies. Next, the rainfall pattern was projected onto the gridded 1o x 1o resolution REACHES (Reconstructing East Asian Climate Historical Encoded Series) (Wang et al., 20018) precipitation index data in 1368-1911CE so that a reconstructed SASM and EASM index can be derived incorporating both temporal and spatial variability. The reconstructed indices were then compared with other indices for justification. Importantly, the reconstructed monsoon indices reveal multidecadal and centennial variabilities during the Little Ice Age. A significant phase transition from SASM dominance shifting to EASM occurred during the Maunder Minimum, coinciding with significant behavior changes of typhoons and other extreme events in East Asia.
How to cite: Lin, K.-H. E., Tseng, W.-L., Lee, J.-I., Lin, C.-W., Hsu, H.-H., and Wang, P. K.: The grand Maunder Minimum and changing patterns of South and East Asian summer monsoons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6842, https://doi.org/10.5194/egusphere-egu25-6842, 2025.
