Annual cycle is fundamental in the East Asian monsoon (EAM) systems, profoundly governing the spatiotemporal distribution of the East Asian rainfall. The present study identified the dominant modes of the annual cycle in the East Asian rainfall based on the Fourier harmonic analysis and the Empirical Orthogonal Function (EOF) decomposition. We evaluated the performance of the first two leading modes (i.e., EOF-1 and EOF-2) in historical experiments (1979–2014) of the 21 released climate models of phase six of the Coupled Model Intercomparison Project (CMIP6). Comparing with the observation, although the CMIP6 models yield the essential fidelity, they still show considerable systematic biases in the amplitude and phase of the annual cycle, especially in east and south China. Most models exhibit substantial phase delays in the EOF-2 mode of the annual cycle. Some specific models (BCC-ESM1, CanESM5, and GFDL-CM4) exhibiting better performance could capture the observed annual cycle and the underlying physics in climatology and interannual variability. The limited fidelity of the EOF-2 mode of the EAM annual cycle primarily hinders the monsoon variability simulation and thus the reliable future projection. Therefore, the dominant modes of the EAM annual cycle act as the evaluate benchmark in the EAM modelling framework. Their improvement could be one possible bias correction strategy for decreasing the uncertainty in the CMIP6 simulation of the EAM.
Nonlinear multi-physics systems and their numerical simulations play an important role in many practical engineering fields, and the development of reliable mathematical methods for uncertainty quantification of such multi-physics systems is still facing great challenges. In this paper, taking the multi-physics models from detonation mechanics and their numerical solution, we briefly introduce recently developed mathematical methods for uncertainty quantification in both complex multi-physics engineering modeling and associated numerical simulation. Also, the strengths and weaknesses of the methods will be discussed, and open problems as well as mathematical challenges will be underlined.
The East Asian monsoon (EAM) exhibits a robust annual cycle with significant interannual variability. Here, the authors find that the EAM annual cycle can be decomposed into the equinoctial and solstitial modes in the combined sea level pressure, 850-hPa low-level wind, and rainfall fields. The solstitial mode shows a zonal pressure contrast between the continental thermal low and the western Pacific subtropical high, reaching its peak in July and dominating the East Asian summer monsoon. The equinoctial mode shows an approximate zonal contrast between the low-level cyclone over the east of the Tibetan Plateau and the western Pacific anticyclone over the east of the Philippines. It prevails during the spring rainy season in South China and reaches its peak in April. The interannual variations of the lead-lag phase of the two modes may result in the negative correlation of rainfall anomalies in North China between spring and fall and in South China between winter and summer, which provides a potential basis for the across-seasonal prediction of rainfall. The warm phase of ENSO in winter could give rise to the reverse interseasonal rainfall anomalies in South China, while the SST anomaly in the Northwest Pacific Ocean may regulate the rainfall anomaly in North China.
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