Precipitation anomalies due to monsoon variability have had a profound impact on the ecological, economic and social life of the densely populated Southeast Asian region.Scientific studies have found that global warming has increased the water vapor content of the atmosphere, which has increased the intensity of monsoon precipitation globally, but there are significant regional differences in the local variability of monsoon precipitation.Numerical model analysis pointed out that due to the influence of atmospheric internal variability, inter-model variability and different greenhouse gas emission scenarios, there are great uncertainties in the future projection of the East Asian monsoon precipitation characteristics by different climate models, among which the influence of model uncertainty maximum.This increases the difficulty of attributing future changes in precipitation in the East Asian monsoon region, and also brings more challenges to numerical model improvement and model prediction of monsoon precipitation.
Prof. Yaocun Zhang's team in the School of Atmospheric Sciences has long been addressing the issue of the mechanism of precipitation change and future projection in the East Asian monsoon region, and has conducted systematic research in terms of the analysis of the mechanism of precipitation change in the monsoon region (Tang et al., 2021), as well as the assessment of numerical model differences and simulation capability (Yang et al., 2019; Huang et al.2022).The latest research work has taken a unique approach to the uncertainty in monsoon precipitation prediction by discussing the future changes of monsoon projection from the perspective of mid-latitude climate dynamics modes, and has achieved innovative results.Inspired by the idea of fingerprinting, the team members and their collaborators use multiple sets of Green's function experiments to construct the most stable modes of the climate dynamics system, called the optimal modes. By applying the optimal mode to multi-ensemble model data,the precipitation mode of East Asian monsoon is projected to be significantly enhanced.
Quantitative analyses of the spatial and temporal characteristics of regional precipitation reveal that under the high global GHG (RCP8.5) emission scenario, precipitation in the middle and lower Yangtze River Basin of China to South Korea and southern Japan will significantly increase by about 29.2% by the end of this century, while precipitation in the North China region as well as in the region of China from South China to the South Asian countries will significantly decrease.The above conclusions are validated in the Sixth International Coupled Model Inter-comparison Program (CMIP6), maintaining a high agreement among different models (Fig. 1), which largely reduces the uncertainty in the projection of monsoon precipitation in East Asia. The results of the study improve the knowledge of the climate model's ability to simulate regional precipitation.
Further quantitative diagnosis of the relative contributions of atmospheric internal dynamics and external thermal factors in the future variation of East Asian monsoon precipitation has been conducted and found that the spatial structure of enhanced-weakened precipitation in the East Asian monsoon region is closely related to the Pacific-Japan teleconnection pattern, and the corresponding lower-level circulation system will increase by about 19.6% by the end of the century, while the lower-level water vapor content will increase by about 13.8%. Distinguishing from the important role of water vapor in the global mean precipitation changes, the results emphasize the major contribution of the internal dynamical processes in the atmosphere characterized by the circulation system to the enhancement of monsoon precipitation in East Asia (accounting for 67%). This plays a constructive role in understanding the sources of regional monsoon precipitation simulation differences, and provides a scientific basis for the simulation and attribution of extremes in the East Asian monsoon region in the future.
The latest research results, titled Robust projection of East Asian summer monsoon rainfall based on dynamical modes of variability, were published in Nature Communications on June 29, 2023.Dr. DaokaiXue, an assistant researcher in Prof. Yaocun Zhang's team in the School of Atmospheric Sciences, is the first author of this paper, and Dr. DaokaiXue and Prof. Jian Lufrom the Pacific Northwest National Laboratory (PNNL) are the co-corresponding authors.Collaborators also include scholars from the Pacific Northwest National Laboratory (PNNL), Lawrence Berkeley National Laboratory (LBNL), Institute of Atmospheric Physics of the Chinese Academy of Sciences (IAP), and Ocean University of China (OUC). This research work was funded by the National Key Research and Development Program of China, the National Natural Science Foundation of China, and the Jiangsu Collaborative Innovation Center for Climate Change.
Figure 1 Future projections of the East Asian monsoon precipitation mode in multi-ensemble models
Xue, D., et al. (2023)Robust projection of East Asian summer monsoon rainfall based on dynamical modes of variability. Nature Communications, 14, 3856.
Huang, D., et al. (2022) Inter-model spread of the simulated East Asian summer monsoon rainfall and the associated atmospheric circulations from the CMIP6 models. Journal of Geophysical Research: Atmospheres, 127(20), e2022JD037371.
Tang, Y., et al. (2021) Drivers ofsummer extreme precipitation eventsover East China. Geophysical ResearchLetters, 48, e2021GL093670.
Yang, B., et al. (2019) Better monsoon precipitation in coupled climatemodelsdue tobias compensation. Nature Partner Journal: Climateand Atmospheric Science. 2,1–8.