Widely distributed proxy records show that there were out-of-phase behaviors of moisture change between arid central Asia (ACA) and monsoonal northern China during the Little Ice Age (LIA) and Medieval Climate Anomaly (MCA). We examined spatial pattern differences between the MCA and LIA to identify contrasting patterns of summer precipitation variability, and to diagnose explanatory mechanisms through the analysis of a 1000-year global climate model simulation driven by natural and anthropogenic forcing. The results show that the model was able to roughly produce the general features of MCA-LIA hydroclimatic spatial differences between monsoonal northern China and ACA, with a relatively wet MCA found in monsoonal northern China and a relatively dry MCA found in ACA. A further analysis of associated circulations shows that increased summer precipitation in monsoonal northern China was caused by the strengthening of summer monsoon, while the decline in summer precipitation in ACA was caused by an anomalous northward displacement of the subtropical westerly jet stream. Our analyses suggest that both effective solar forcing and El-Niño Southern Oscillation (ENSO) may produce these contrasting patterns of precipitation between monsoonal northern China and ACA. Due to a change in the probability of ENSO phases at the centennial time scale found in our experiments may be attributed to solar irradiances, higher effective solar irradiances during the MCA relative to those of the LIA may have been the ultimate forcing mechanism for the simulated precipitation differences between the MCA and LIA.
Bibliographical noteFunding Information:
Acknowledgements This work was supported by the National Natural Science Foundation of China (grant # 41605046), the National Basic Research Program of China (grant # 2013CB955904, 2013CB955902), the National Natural Science Foundation of China (grant # 41230524), the Fundamental Research Funds for Central Universities (grant #1191320019), the 2013 Yunnan project for the introduction of advanced talents (grant #2013HA024) and by a grant from the U.S. Department of Energy Office of Science (BER). Kenneth Shen is thanked for his helpful reviewing and English improvement of the manuscript. We acknowledge the critical comments from anonymous reviewers and editor.
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- Last millennium
- Solar irradiance