1380—1429年中国东部雨涝期与气候系统内部变率的可能联系

The possible role of the internal variability of the climate system in hydroclimate over eastern China during 1380—1429

利用重建数据和模拟数据探讨中国东部1380-1429年雨涝期与气候系统内部变率之间的联系。结果显示:1380-1429年全球大多数区域发生了严重的旱涝事件,揭示了中国东部雨涝气候可能是对大尺度大气环流调整下的响应,可能与该时期赤道太平洋类La Nina海温分布、太平洋年代际振荡(PDO)冷位相、北大西洋年代际振荡(AMO)暖位相、北大西洋涛动(NAO)正位相相关。全球海气耦合模式尽管能够模拟出该时期非洲和欧洲区域的干湿空间分布状况,但模拟的中国东部、北美和南美的干湿状况与重建相反。其可能的原因或许是模式虽正确模拟出了NAO正位相及弱的印度洋偶极子(IOD)负位相,但无法正确刻画赤道太平洋类La Nina海温分布、北太平洋PDO冷位相及北大西洋AMO暖位相。

Background, aim, and scope The occurrence of severe persistent pluvials during the summer monsoon season is perhaps one of the most pressing climate concern that faces China today. However, few works have focused on understanding the occurrence of the severe persistent pluvials in China, although studies to date have revealed some severe persistent pluvials over the last thousand years. The proxy data show the most wet period occurring from 1330s to 1420 s over eastern China during the last 1500 years. Here, we focus on pluvial occurring in this period to assess the possible role of the internal variability of the climate system in hydroclimate over eastern China. Materials and methods The role of the internal variability of the climate system in driving the pluvial over eastern China is assessed by using the model data and paleo-proxy records. Results Based on proxy data, one such pluvial have occurred from 1380 to 1429 during this wet period. The hydroclimatic pattern in global which suggested by proxy records during 1380 to 1429 AD highlight relate regionally coherent climate changes with pluvials over eastern China. Such hydroclimatic pattern indicates coherent shifts in large-scale hydroclimatic patterns during this eastern China pluvial era which is similar with the climate dynamics associated with the internal variability of the climate system. These internal variability include persistent La Ni?a-like conditions in the tropical Pacific, the cool phase of the Pacific Decadal Oscillation(PDO), the warm phase of the Atlantic Multidecadal Oscillation(AMO) and the positive North Atlantic Oscillation(NAO) index during this time. The CCSM2.0 simulations of climate for the period 1380—1429 AD are shown to reproduce many aspects of hydroclimate found in paleo-proxy records for much of the eastern Hemisphere, northern Eurasia, with the noticeable exception of North and South America and eastern China, which strongly linked to ENSO. For the internal variability conditions, the model could not produce the negative ENSO and its low-frequency counterpart PDO have been shown by proxy records, although it could roughly produce the positive NAO phase. Discussion The eastern China pluvial era as existing paleoclimatic archives are shown to be part of a global hydroclimatic regime linked to persistent La Ni?a-like conditions in the tropical Pacific, the cool phase of the Pacific Decadal Oscillation, the warm phase of the Atlantic Multidecadal Oscillation and the positive North Atlantic Oscillation index during this time. Furthermore, CCSM2.0 model driven by solar forcings and volcanic forcing does not display pluvial during 1380—1429 AD that would support the possibility suggested by the proxy-record that this pluvial may be related to internal variability. Finally, the model could not produce the pluvial during 1380—1429 AD over eastern China attribute to the model could not produce the climate dynamics associated with the ENSO and its low-frequency counterpart PDO. Conclusions Thus, we conclude both our analyses of reconstructions and simulations reveal the internal variability may play an important role in causing the pluvial during 1380—1429 AD over eastern China and could explain many features of global hydroclimate changes during this time. It is found that the ENSO and its low-frequency counterpart PDO may play an important role in determining hydroclimatic variability over China and North and South America. In addition, AMO and NAO may also have their own contributions to the pluvial during 1380—1429 AD over eastern China. Recommendations and perspectivesHowever, additional high-resolution and absolutely-dated paleohydrological records are critically needed to expand their spatiotemporal coverage in order to definitively establish the more realistic hydroclimatic pattern during this period and to reveal more robust relationship between the internal variability of the climate system in hydroclimate over eastern China during 1380—1429.