Simulated Interannual Teleconnection Between the Summer North Atlantic Oscillation and Summer Precipitation in Eastern China During the Last Millennium

2018 ◽  
Vol 45 (15) ◽  
pp. 7741-7747 ◽  
Author(s):  
Youbing Peng
2019 ◽  
Vol 19 (16) ◽  
pp. 10787-10800 ◽  
Author(s):  
Juan Feng ◽  
Jianping Li ◽  
Hong Liao ◽  
Jianlei Zhu

Abstract. The high aerosol concentration (AC) over eastern China has attracted attention from both science and society. Based on the simulations of a chemical transport model using a fixed emissions level, the possible impact of the previous autumn North Atlantic Oscillation (NAO) combined with the simultaneous El Niño–Southern Oscillation (ENSO) on the boreal winter AC over eastern China is investigated. We find that the NAO only manifests its negative impacts on the AC during its negative phase over central China, and a significant positive influence on the distribution of AC is observed over south China only during the warm events of ENSO. The impact of the previous NAO on the AC occurs via an anomalous sea surface temperature tripole pattern by which a teleconnection wave train is induced that results in anomalous convergence over central China. In contrast, the occurrence of ENSO events may induce an anomalous shift in the western Pacific subtropical high and result in anomalous southwesterlies over south China. The anomalous circulations associated with a negative NAO and El Niño are not favorable for the transport of AC and correspond to worsening air conditions over central and south China. The results highlight the fact that the combined effects of tropical and extratropical systems play a considerable role in affecting the boreal winter AC over eastern China.


2009 ◽  
Vol 5 (2) ◽  
pp. 129-141 ◽  
Author(s):  
C. Shen ◽  
W.-C. Wang ◽  
Y. Peng ◽  
Y. Xu ◽  
J. Zheng

Abstract. We use measurements of recent decades, 1500-yr proxy data, and millennium model simulations with a variety of climate facings to study the temporal and spatial variability of summer precipitation over eastern China. Spectral analysis of the proxy data using multi-taper method reveals three statistically significant bidecadal (15–35-yr), pendadecadal (40–60-yr), and centennial (65–170-yr) oscillation bands. The results of wavelet filtering show that the amplitudes of these bands vary substantially through time depending on the temperature regimes. Weak centennial oscillation and strong pentadecadal oscillation occur in warm conditions, whereas both the centennial and pentadecadal oscillations are strong in cold conditions. A model/data intercomparison suggests that pentadecadal and bidecadal oscillations could be associated with internal variability of the climate system. It is also found that the increased frequency of drought-in-north/flood-in-south spatial pattern over eastern China during the last two decades is unusual in the past five centuries.


2017 ◽  
Author(s):  
Jian Shi ◽  
Qing Yan ◽  
Huijun Wang

Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variation based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past time remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase Ⅲ and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) enhanced in the Medieval Climate Anomaly (MCA; ~ 950–1250 A.D.), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ~ 1500‒1800 A.D.), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a multi-decadal timescale. The nonstationary multi-decadal EASM-precipitation relationship broadly exhibits a quasi-60-year period, which may be attributed to the internal variability of the climate system and have no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.


2018 ◽  
Vol 14 (4) ◽  
pp. 577-591 ◽  
Author(s):  
Jian Shi ◽  
Qing Yan ◽  
Huijun Wang

Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variations based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM–precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase III and Community Earth System Model to investigate the stability of the EASM–precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) was enhanced in the Medieval Climate Anomaly (MCA; ∼ 950–1250 AD), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ∼ 1500–1800 AD), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM–precipitation relationship is only stable on a centennial and longer timescale and is unstable on a shorter timescale. The nonstationary short-timescale EASM–precipitation relationship broadly exhibits a multi-decadal periodicity, which may be attributed to the internal variability of the climate system and has no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.


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