Comparisons on characteristics and mechanisms of the decadal megadroughts over eastern China between MCA and LIA

Abstract

In this study, simulations of 13 all‐forcing experiments from the Community Earth System Model Last Millennium Ensemble (CESM‐LME) archive were used to investigate the different spatiotemporal characteristics and corresponding mechanisms of the decadal megadroughts over the eastern China during two typical periods in the past millennium, that is, Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). The results show that there is no significant difference in either megadrought intensity or duration between the MCA and LIA, but there are significant differences in the megadrought frequencies. The frequency of megadroughts during the MCA is 1.44 times/hundred years, compared with 1.69 times/hundred years in LIA. Results from solar only sensitivity experiments and volcanic only sensitivity experiments show that this difference is mainly induced by the solar radiation. The mechanism analyses show that a spatial pattern of sea surface temperature anomalies (SSTA) resembling the positive Pacific Decadal Oscillation (PDO)‐like pattern have occurred simultaneously with the megadroughts during both the MCA and LIA. While, the megadroughts in MCA are strongly correlated with the strong PDO‐like SSTA patterns, and the megadroughts in LIA are strongly correlated with the weak PDO‐like SSTA patterns. In addition, the anomalous sea level pressure (SLP) field and wind field associate with the megadroughts during the MCA and LIA are consistent with the strengths of SSTA, with significant larger SLP and wind anomalies during the MCA than those during the LIA. Therefore, it can be concluded that the responses of the large‐scale atmospheric circulation patterns to SSTA are similar during these two typical periods, and the difference in the megadrought frequencies is due to the nonlinear response of the precipitation variability to the large‐scale atmospheric circulation patterns.

Assessing the Modern Multi‐Decadal Scale Aridification Over the Northern China From a Historical Perspective

“…Jin et al (2019) found that a strong 11-year solar cycle can excite an anomalous SST pattern that resembles a negative PDO phase, and enhance the decadal variability of EASM through excitation of a coupled decadal mode in the Asia-North Pacific region. Xue et al (2020) also confirmed that the droughts in Little Ice Age, which refers a period of weaker solar radiation, are stronger and more correlated with PDO-like SST patterns when compared with droughts in Medieval Climate Anomaly.…”

“…Xue et al. (2020) also confirmed that the droughts in Little Ice Age, which refers a period of weaker solar radiation, are stronger and more correlated with PDO‐like SST patterns when compared with droughts in Medieval Climate Anomaly.…”

“…There are many similar decadal to multi-decadal scale drought/aridification events over northern China during last millennium, which also brought tremendous impacts to society and environment (Hua et al, 2013;Shen et al, 2007;Zheng et al, 2006). For the mechanisms behind these drought events, natural external forcings (i.e., volcanic eruptions and solar radiation) have strong influences (Ning et al, 2020;Qin et al, 2020;Xue et al, 2020), through directly weaking the EASM associated with reduced ocean-land thermal contrast (Chen et al, 2020;Man et al, 2014;Peng et al, 2014), and changing the PDO and AMO phases (Ning et al, 2020;Wang et al, 2012). Solar activities are also significantly correlated to the decadal precipitation variability over northern China during the last millennium (Ge et al, 2016;Jin et al, 2019;Zhao et al, 2012).…”

Combined Impacts of the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation on Summer Precipitation in Eastern China During the Medieval Climate Anomaly and Little Ice Age

“…In comparison, the positive phase of the PDO caused a precipitation deficit over the Yangtze‐Huai River Valley and an excess over South and North China during the MCA, but induced a uniform deficit in eastern China during the LIA. The unstable responses of ECSP to the PDO during the two typical periods were further confirmed based on the Community Earth System Model‐Last Millennium Ensemble (CESM‐LME) simulations (Xue et al., 2021). In other words, the ECSP patterns only induced by the AMO/PDO were different between the MCA and LIA, and also differed from the patterns at present.…”

Future risk of decadal megadrought events over eastern China based on IPO-constrained precipitation

“…33 ), are the leading modes on decadal scale. They are found to contribute largely to regional decadal precipitation variability [34][35][36][37] , especially to eastern China [38][39][40][41] . In recent decades, PDO/IPO phase shifted from positive to negative, and caused EASM weakening and the less precipitation over northern part of eastern China since the late 1970s 26,42,43 .…”