doi:  10.3878/j.issn.1006-9895.1809.18145
亚洲夏季风30~60天季节内振荡对中国东部地区持续性极端降水的影响

Impact of the 30?60-day Boreal Summer Intraseasonal Oscillation over the Asian Summer Monsoon Region on Persistently Extreme Rainfall over Eastern China
摘要点击 667  全文点击 99  投稿时间:2018-04-08  修订日期:2018-07-13
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基金:  国家自然基金项目(91537103, 41730963)、中国科学院前沿科学重点研究项目(QYZDY-SSW-DQC018)、中国地质大学(武汉)杰出人才培育基金(CUG170643)和气象灾害教育部重点实验室(南京信息工程大学)开放课题(KLME1702),国家自然科学基金
中文关键词:  持续性极端降水, 大气季节内振荡, 年际变化
英文关键词:  persistently extreme rainfall  atmospheric intraseasonal oscillation  interannual variation
     
作者中文名作者英文名单位
李健颖Li Jian Ying南京信息工程大学气象灾害教育部重点实验室 南京,中国地质大学(武汉)
毛江玉Mao Jiang Yu中国科学院大气物理研究所
引用:李健颖,毛江玉.2019.亚洲夏季风30~60天季节内振荡对中国东部地区持续性极端降水的影响[J].大气科学
Citation:Li Jian Ying,Mao Jiang Yu.2019.Impact of the 30?60-day Boreal Summer Intraseasonal Oscillation over the Asian Summer Monsoon Region on Persistently Extreme Rainfall over Eastern China[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      本文基于1979~2015年中国台站观测的格点化高分辨率降水和NCEP II大气再分析逐日资料,探讨了亚洲季风区夏季30~60天大气季节内振荡(ISO)与长江中下游地区持续性降水异常的关系,重点揭示了南亚和东亚子季风区ISO的相互作用及二者协同引起长江中下游持续性极端降水的物理机制。合成分析表明,南亚和东亚ISO是通过高层辐散环流发生相互作用。在ISO位相1~3(5~7),异常活跃(抑制)对流从赤道印度洋北传至孟加拉湾?印度次大陆区域,其伴随的高层异常辐散(辐合)环流通过补偿效应,引起南海?热带西北太平洋的异常高层辐合(辐散),加强了局地的异常下沉(上升)运动,有利于南海?西北太平洋的异常抑制(活跃)对流发展并维持。南海?西北太平洋的异常抑制(活跃)对流伴随着显著的斜压散度,并进一步激发出一个连接南海和长江中下游的经向垂直环流圈,引起长江中下游强烈的异常上升(下沉)运动和低层水汽辐合(辐散),使得降水持续性偏多(少),极端降水的发生概率持续地偏高(低),有利于(不利于)形成持续性极端降水事件。研究还表明,亚洲季风区ISO的强度存在显著的年际变化,并对长江中下游持续性极端降水的发生频次和持续时间具有调制作用。在ISO偏强(弱)年,长江中下游持续性极端降水的发生频次较高(低),且持续时间较长(短)。
Abstract:
      The daily high-resolution gridded station-observed rainfall over China and NCEP-DOE AMIP-II atmospheric reanalysis datasets for the period 1979–2015 are used to investigate the impact of the 30–60-day atmospheric intraseasonal oscillation (ISO) over the Asian monsoon region on persistently anomalous rainfall over the middle and lower reaches of Yangtze River (MLYR; 25o~30oN,110o~120oE), revealing the interaction between ISOs over two sub-monsoon areas of the South Asia and East Asia as well as the physical mechanism for the ISOs influencing coordinatedly the persistently extreme rainfall over the MLYR. Composite analyses demonstrate that the ISO over the South Asian monsoon region interacts with the counterpart over the East Asian monsoon region through upper-level divergent flows. During phases 1?3 (5?7) of the ISO, active (inactive) convection anomalies propagate northward from the equatorial Indian Ocean to the Indian Subcontinent?Bay of Bengal. The accompanied divergence (convergence) anomalies in the upper troposphere cause the downstream anomalous convergence (divergence) over the South China Sea?western North Pacific (SCS?WNP) through compensation effect, leading to anomalous descents (ascents) locally over the SCS?WNP, and therefore favoring the development and persistence of anomalous inactive (active) convection anomalies. Such inactive (active) convection anomalies are characterized by prominent baroclinic divergence structure and further trigger a meridional-vertical circulation cell between the SCS and the Yangtze Basin, resulting in anomalous ascents (descents) and low-level moisture convergence (divergence) over the MLYR. As a consequence, positive (negative) rainfall anomalies continuously arise over the MLYR, with the occurrence probability of extreme rainfall significantly increasing (decreasing), favorable (unfavorable) for the occurrence of persistently extreme rainfall events. Moreover, the intensity of ISO over the Asian monsoon region exhibits strong interannual variations and further modulates the frequency and duration of persistently extreme rainfall events occurring over the MLYR. In strong (weak) ISO years, more (fewer) persistently extreme rainfall events with longer (shorter) durations occur over the MLYR.
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