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1.
利用中国北方季风区46站盛夏降水观测资料,采用经验正交函数分解(EOF)、合成分析和相关分析等方法,将盛夏北方季风区划分为4类雨型:A型全区一致偏多、B型全区一致偏少、C型华北偏多东北偏少和D型华北偏少东北偏多,并对比分析了四类雨型同期大气环流和前期至同期海温演变特征的差异,以探讨其形成机制及前期预测信号。结果表明:四类雨型对应的东亚大气环流和海温演变具有明显的差异。A型年:东亚副热带西风急流(西风急流)和西太平洋副热带高压(西太副高)位置偏北,东亚夏季风偏强,欧亚中高纬以纬向环流为主,北方季风区低层辐合、高层辐散,冷暖空气在北方季风区辐合;从前冬至夏季,赤道中东太平洋类似于东部型La Ni?a发展年的海温异常分布,北大西洋海温三极子模态(NAT)负位相逐渐形成;B型年则基本相反。C(D)型年:西风急流异常偏北(略偏南),西太副高偏西(东)偏北,华北盛行西南(西北)风,东北盛行东北(东南)风,华北地区对流层低层辐合(辐散)高层辐散(辐合),东北地区对流层低层辐散(辐合)高层辐合(辐散),东北冷涡较弱(活跃);从前冬至夏季,赤道中东太平洋和印度洋逐渐由暖海温向冷海温转变(El Ni?o分布形态逐渐形成)。  相似文献   

2.
利用1979-2015年海洋和大气再分析资料,基于夏季太平洋-日本遥相关型(PJ)指数,讨论了PJ指数在极端正负年份长江中下游降水位置和强度异常的不对称响应及其可能原因。结果表明:在PJ负位相年(对应El Niňo次年),长江中下游降水显著偏多,中心分别位于江淮流域和日本南部;而在PJ正位相年(对应La Niňa次年),长江中下游降水减少却不明显。研究发现:在PJ负位相年,中东太平洋、印度洋、南海地区海温明显偏暖,菲律宾海上空有异常反气旋响应,长江中下游地区有异常气旋响应;而在PJ正位相年则反之。在PJ负(正)位相年,菲律宾海异常反气旋(气旋)和长江中下游地区异常气旋(反气旋)明显偏强(偏弱),由此导致长江中下游降水位置和强度异常存在不对称响应。基于大气环流模式ECHAM4.8的敏感性数值试验结果表明,即使印度洋海温偏暖与偏冷程度相当,但由偏暖印度洋海温激发的菲律宾海异常反气旋也明显偏强,从而造成长江中下游地区降水偏多程度大于偏少程度。由此印证的事实是:El Niňo次年(PJ负位相年)长江中下游夏季降水偏多的预测技巧高于La Niňa次年夏季降水偏少的预测技巧。  相似文献   

3.
广州春季降水的变化及其前兆信号   总被引:8,自引:4,他引:8       下载免费PDF全文
广州春季降水存在以准2年为主的年际变化和以30年为主的年代际变化,目前处于年代际尺度上的少雨时段。Nino3区的海温异常是广州春季降水最强的前兆信号,它与广州春季降水的显著正相关在前一年的11月份就已出现,并且一直稳定维持到4月份。前冬Nino3区海温异常对广州春季降水的影响是通过影响春季北太平洋副热带高压和低层风场异常实现的。前冬Nino3区海温正异常时,春季副热带高压偏强、位置偏西,华南处于副高边缘垂直运动的上升区,菲律宾以东的低层反气旋环流增加了向华南的水汽输送,从而使得广州春季降水偏多;前冬Nino3区海温负异常时,副热带高压偏弱、位置偏东,华南地区远离副高、处于垂直运动的下沉区,菲律宾以东低层为气旋环流控制,华南地区盛行偏北气流,不利于水汽的向北输送,从而使得广州春季降水偏少,造成春旱。  相似文献   

4.
中国夏季降水对南印度洋偶极子的响应研究   总被引:11,自引:2,他引:11  
杨明珠  丁一汇 《大气科学》2007,31(4):685-694
分析了春季印度洋海表温度(SST)与中国160个站夏季降水的关系,得到:印度洋全海盆的增温趋势与我国夏季降水的气候线性变化趋势是十分一致的。另外,热带外南印度洋出现西南印度洋为正(负)、其东北部出现(负)正海温异常的分布模态时,定义为正(负)南印度洋偶极子PSIOD(NSIOD)事件。SIOD事件对中国夏季降水具有重要影响,PSIOD年,5月份中国江南和西南以及长江中下游的降水偏多;6~8月份华北、东北区域、长江中游以及华南地区降水增多,华南与华北之间的区域降水偏少,即主要为两条雨带的分布。NSIOD年,5月份中国大部降水偏少; 6~8月中国西南、江南地区以及黄淮地区降水偏多。不同时段SIOD所起的作用是不同的,5月,SIOD主要通过改变马斯克林局地环流的变化,影响印度洋低层越赤道的水汽通量输送;6~8月,通过改变海洋大陆下垫面SST热状态,改变其上空对流强度以及水汽输送方向,并间接影响西北太平洋副热带高压的强度和南北位置,进而对中国雨带的分布产生影响。  相似文献   

5.
2016年和1998年汛期降水特征及物理机制对比分析   总被引:12,自引:1,他引:11  
利用多种大气环流、海表温度、积雪面积等数据,并利用个例对比分析和统计方法,研究了2016年汛期(5-8月)中国旱、涝特征及与1998年的异同点,并对比分析了这两年导致降水异常的大气环流和外强迫因子。结果表明:(1)2016年汛期中国降水总体偏多,长江中下游和华北各有一支多雨带。与1998年相比,这两年南方多雨带均位于长江流域,梅雨雨量均较常年偏多1倍以上,但梅雨季节进程有显著差异,1998年发生典型的“二度梅”,而2016年梅雨结束后长江流域降水显著偏少,主要降水区移至北方。(2)2016年5-7月乌拉尔山高压脊明显偏弱,而1998年欧亚中高纬度呈“两脊一槽”型,这与北大西洋海温距平在这两年前冬至春季几乎完全相反的分布型密切相关。(3)这两年5-7月热带和副热带地区环流较为相似,副热带高压偏强、偏西,东亚夏季风偏弱,来自西北太平洋的水汽输送通量均在长江中下游形成异常辐合区,这主要是受到了前期相似的热带海温异常的影响,均为超强厄尔尼诺事件和热带印度洋全区一致偏暖模态。(4)这两年8月环流形势有显著差异,2016年8月副热带高压断裂,西段与大陆高压结合持续控制中国东部上空,夏季风迅速转强,长江流域高温少雨。而1998年8月夏季风进一步减弱,长江流域发生“二度梅”。2016年8月MJO异常活跃并长时间维持在西太平洋地区,激发频繁的热带气旋活动,对副热带地区大气环流的转折有重要作用。而1998年8月MJO主要活跃在印度洋地区,使得副高持续前期偏强的特征。除海洋和上述环流差异外,2016年前冬至春季青藏高原积雪的冷源热力效应远不及1998年强,这可能是导致2016年夏季风偏弱的程度不及1998年,而2016年汛期华北降水较1998年偏多的原因之一。   相似文献   

6.
利用NOAA(National Oceanic and Atmospheric Administration)海温、GPCP(Global Precipitation Climatology Project)降水和ERA-20C(ECMWF's first atmospheric reanalysis of the 20th century)再分析大气环流资料,结合大气环流模式ECHAM5敏感性试验,研究了与秋季印度洋海温偶极子模态(IOD)相联系的冬季热带西太平洋海温异常型及其对东亚冬季气候的影响。发现在秋季发生IOD背景下,冬季西太平洋存在两类海温异常的变化型:一类是西太平洋区域一致偏暖/冷的模态,另一类是区域西冷东暖/西暖东冷的模态。尽管西太平洋海温一致偏暖和西冷东暖这两类海温变化型均有利于华南冬季少降水,但影响的范围有所不同。一致偏暖型引起的少降水范围较大,从华南扩展到长江中下游地区。西冷东暖型引起少降水范围主要限于华南,而在长江中下游到华北则降水偏多。相应地,在大气环流上,尽管两类海温异常型均有利于在西北太平洋菲律宾海附近出现气旋式环流异常,但气旋的强度和中心位置有差异。一致偏暖型引起的气旋偏强,中心位置偏西,其后部异常东北风控制的范围更大,导致少降水范围更大,而西冷东暖型引起的气旋偏弱,中心位置偏东,其后部异常东北风控制的范围小,导致少降水区域主要在华南沿海。本文结果对认识IOD调制随后冬季东亚降水异常的机理有重要意义。  相似文献   

7.
利用 1981—2019 年 NCEP/NCAR再分析资料和观测降水资料,对山东5月降水多(少)雨年环流特征进行分型,分析前期海温影响大气环流进而影响降水的过程。结果表明:典型多(少)雨年,亚洲中高纬环流呈“-、+”(“+、-” )距平分布,盛行纬(经)向环流,东亚大槽偏弱(强)。前期冬春季黑潮区和热带印度洋海温是影响山东5月降水的关键外强迫因子,黑潮区海温偏暖(冷)时,其上空500 hPa高度场为明显正(负)距平,低层风场呈现异常反气旋(气旋),山东受异常东南风(偏西风)控制,加强(削弱)了水汽输送, 利于降水偏多(少)。热带印度洋偏暖年,山东地区 500 hPa高度场上表现为西低东高,低层处于异常反气旋后部的东南气流中,这与典型多雨年的环流特征基本一致,印度洋偏冷年对应环流特征与偏暖年大致相反。  相似文献   

8.
印度洋海温偶极振荡对东亚环流及降水影响   总被引:4,自引:10,他引:4  
利用NCEP/NCAR提供的50a再分析资料、英国气象局全球海温资料、中国气象局整编的160站降水资料,采用相关、合成、奇异值分解等方法讨论了印度洋海温异常偶极振荡对东亚夏季大气环流及降水的影响。结果表明:印度洋海温偶极振荡异常,引起了大气环流的异常,影响了季风强度和雨带分布。印度洋海温偶极振荡正位相年时,印度洋上为东风异常,西太平洋副高偏西、偏南、偏强,菲律宾附近对流活动减弱,东亚夏季风偏强,华南夏季降水偏多;印度洋海温偶极振荡负位相年时,西太平洋副高偏东、偏北,东亚夏季风偏弱,长江黄河之间有异常辐合,降水偏多。  相似文献   

9.
文章对近50a(1961—2010年)内蒙古呼伦贝尔地区的年、汛期和冬春季降水量和降水距平百分率(R%)作了统计,发现年R%和冬春季R%呈上升趋势,汛期R%略呈下降趋势;通过对年R%与大气环流指数、海温的相关分析发现:前期副热带高压(副高)、北半球极涡、大西洋欧洲环流C型、西藏高原位势高度和印缅槽(南支槽)强度指数等均与年R%密切相关,当北半球极涡收缩、强度减弱,副高扩张、强度加强,西藏高原位势高度偏高,南支槽减弱时,有利于来年呼伦贝尔地区降水,否则,相反。此外,前一年夏季北印度洋海域和赤道东太平洋海域海温对呼伦贝尔地区来年降水有显著影响,这两块海区的海温和上述环流指数可考虑作为呼伦贝尔地区年降水的预测信号使用。  相似文献   

10.
顾薇  陈丽娟 《气象》2019,45(1):126-134
为更好地了解2018年夏季(6—8月)我国主要气候异常特征及成因,本文利用我国气象要素站点资料、再分析大气环流资料和全球海温数据分析了2018年夏季我国降水和气温的异常特征、东亚大气环流特征及海温对我国气候的影响。结果显示2018年夏季全国平均降水量较常年同期偏多9.6%,我国中东部地区降水呈现“南北多、中间少”的分布特征,北方和华南大部降水较常年同期偏多、长江中下游降水明显偏少。降水的上述异常特征受到东亚副热带和中高纬大气环流的共同影响。2018年夏季东亚副热带高空急流和西太平洋副热带高压位置都明显偏北,东亚沿岸由南至北为“负—正—负”的高度距平分布, 呈现出“东亚—太平洋型”遥相关负位相的特征,菲律宾附近对流层低层大气维持异常的气旋式环流,东亚副热带夏季风异常偏强。同时,欧亚中高纬度大气呈现“两槽一脊”的异常高度分布特征。在副热带和中高纬大气环流的这种配置下,我国北方地区以异常偏南风为主,有利于暖湿气流的输送,降水偏多;华南地区在偏强的热带对流活动影响下,降水也总体偏多;而长江中下游地区则以明显的辐散下沉运动为主,降水偏少。从外强迫因子来看,2017年10月至2018年4月发生的La Nina事件对东亚夏季风偏强及我国降水“南北多、中间少”的异常特征起到了重要作用。  相似文献   

11.
利用中国2374个站点的日最高气温资料、NCEP/NCAR大气环流资料以及NOAA海表温度资料,分析了中国南方盛夏高温的主要类型,比较了各类型高温对应的大尺度环流以及与海表温度异常信号的联系。结果表明:中国南方地区年高温日数有明显的增多趋势,利用聚类分析将中国南方盛夏高温分为江淮型、华南型和华中型3类。江淮型高温中心区域位于江淮地区,该类型高温空间范围大、发生频次高,典型的环流系统为高、低空呈现异常反气旋,西太平洋副热带高压(西太副高)偏强偏西,南北位置略偏北。该类型高温是西太副高直接控制下的高温类型,与前冬到夏季中部型厄尔尼诺衰减和春季赤道大西洋地区海温偏高有关。华南型高温中心区域在江南南部到华南地区,典型的环流系统是东亚副热带急流的位置偏南,西太副高偏强、偏西和脊线偏南,华南型高温也是西太副高直接控制下的高温,且伴随着西南季风的减弱,干热特征明显,该类型高温与东部型厄尔尼诺衰减及其与之相联系的印度洋“电容器”效应密切相关。华中型高温主要位于湖北和湖南两省,对应的环流型为西太副高偏弱、偏东,在中高纬度与北大西洋-欧亚遥相关型类似,是大陆高压控制下的高温,使得水汽条件比另两类高温好。北大西洋-欧亚遥相关型是华中型高温的可能信号源。   相似文献   

12.
中国东部季风区夏季四类雨型的水汽输送特征及差异   总被引:2,自引:1,他引:1  
利用1951~2015年NCEP/NCAR再分析逐日资料和中国160站月降水观测资料,及中国东部季风区夏季四类雨型(北方型、中间型、长江型和华南型)的划分结果,分析了东亚水汽输送与中国东部季风区夏季降水的关系,比较了四类雨型的水汽输送、收支特征及其差异,结果表明:(1)夏季影响中国东部季风区的水汽通道主要有以下6条:印度洋通道,表征印度季风区偏南的西风水汽输送;高原南侧通道,表征印度季风区偏北的西风水汽输送;太平洋通道,表征由西太平洋副热带高压(副高)带来的西太平洋的水汽;西风带通道,表征西风带的水汽输送;孟加拉湾通道,表征来自孟加拉湾向北的水汽输送;南海通道,表征来自印度洋和孟加拉湾在中南半岛转向及来自南海的水汽;与中国东部不同地区降水异常相联系的水汽通道存在明显的差异,且同一条水汽通道在夏季不同阶段与降水的关系也不尽相同。(2)四类雨型的水汽输送和收支特征有明显的差异,华北盛夏降水主要受亚洲季风水汽输送的影响,其次是西风带水汽输送,北方型年二者往往偏强,尤其是季风水汽输送增加一倍以上,贡献也明显增加,20世纪70年代中期之后,季风水汽输送显著减弱,西风带水汽输送的重要性相对增大;淮河流域夏季降水异常主要受太平洋通道水汽输送异常的主导,其次是高原南侧通道水汽输送,二者偏强并在淮河流域辐合时,淮河流域降水偏多形成中间型年;长江中下游地区夏季降水主要受太平洋通道水汽输送异常的主导,长江型年,副高西北侧的西南水汽输送异常加强,并与北方冷空气异常在长江中下游地区辐合,区域为正的水汽净收支;华南地区夏季降水则受印度洋通道、太平洋通道及南海通道的共同影响,当三条通道异常偏强,水汽与北方冷空气在华南地区辐合,形成华南型年。本研究所得结论加深了我们对四类雨型形成机理的认识,并为汛期主雨带的预测提供了参考。  相似文献   

13.
The interannual variability of autumn precipitation over South China and its relationship with atmospheric circulation and SST anomalies are examined using the autumn precipitation data of 160 stations in China and the NCEP-NCAR reanalysis dataset from 1951 to 2004. Results indicate a strong interannual variability of autumn precipitation over South China and its positive correlation with the autumn western Pacific subtropical high (WPSH). In the flood years, the WPSH ridge line lies over the south of South China and the strengthened ridge over North Asia triggers cold air to move southward. Furthermore, there exists a significantly anomalous updraft and cyclone with the northward stream strengthened at 850 hPa and a positive anomaly center of meridional moisture transport strengthening the northward warm and humid water transport over South China. These display the reverse feature in drought years. The autumn precipitation interannual variability over South China correlates positively with SST in the western Pacific and North Pacific, whereas a negative correlation occurs in the South Indian Ocean in July. The time of the strongest lag-correlation coefficients between SST and autumn precipitation over South China is about two months, implying that the SST of the three ocean areas in July might be one of the predictors for autumn precipitation interannual variability over South China. Discussion about the linkage among July SSTs in the western Pacific, the autumn WPSH and autumn precipitation over South China suggests that SST anomalies might contribute to autumn precipitation through its close relation to the autumn WPSH.  相似文献   

14.
The Dipole Mode of the Summer Rainfall over East China during 1958–2001   总被引:2,自引:0,他引:2  
By examining the second leading mode(EOF2)of the summer rainfall in China during 1958–2001 and associated circulations,the authors found that this prominent mode was a dipole pattern with rainfall decreasing to the north of the Yangtze River and increasing to the south.This reverse relationship of the rainfalls to the north and to the south of the Yangtze River was related with the meridional circulations within East Asia and the neighboring region,excited by SST in the South China Sea-northwestern Pacific....  相似文献   

15.
宗海锋  张庆云  陈烈庭 《大气科学》2006,30(6):1189-1197
利用1961~2000年中国台站降水资料、 NCEP/NCAR再分析资料以及扩展重建海平面温度 (Extended Reconstructed Sea Surface Temperatures, ERSST) 资料, 采用EOF、小波变换、合成及相关方法探讨中国东部梅雨期降水的时空变化及其环流、水汽输送和海温异常特征.分析指出中国东部梅雨期 (6月11日~7月10日) 降水存在三种主要空间型: 江南北部多雨型、长江流域多雨型和江淮平原多雨型.三种降水型都存在多时间尺度特征, 由于年际和年代际振荡的周期和强度随时间的变化有不同表现, 三种雨型旱涝年出现的年份有所不同.三种雨型对应的东亚夏季风环流各子系统的强度、位置、水汽输送等也存在明显差异.梅雨期三种雨型与冬季海温的研究表明:赤道东太平洋海温偏高有利于出现江南北部降水型; 赤道印度洋、南海和西太平洋黑潮海温偏高有利于出现长江流域降水型; 北太平洋中纬度海温偏高则有利于出现江淮平原降水型.  相似文献   

16.
The characteristics of droughts and floods in China during the summers (May–August) of 2016 and 1998 were compared in great detail, together with the associated atmospheric circulations and external-forcing factors. Following results are obtained. (1) The precipitation was mostly above normal in China in summer 2016, with two main rainfall belts located in the Yangtze River valley (YRV) and North China. Compared with 1998, a similar rainfall belt was located over the YRV, with precipitation 100% and more above normal. However, the seasonal processes of Meiyu were different. A typical “Secondary Meiyu” occurred in 1998, whereas dry conditions dominated the YRV in 2016. (2) During May–July 2016, the Ural high was weaker than normal, but it was stronger than normal in 1998. This difference resulted from fairly different distributions of sea surface temperature anomalies (SSTAs) over the North Atlantic Ocean during the preceding winter and spring of the two years. (3) Nonetheless, tropical and subtropical circulation systems were much more similar in May–July of 2016 and 1998. The circulation systems in both years were characterized by a stronger than normal and more westward-extending western Pacific subtropical high (WPSH), a weaker than normal East Asian summer monsoon (EASM), and anomalous convergence of moisture flux in the mid and lower reaches of the YRV. These similar circulation anomalies were attributed to the similar tropical SSTA pattern in the preceding seasons, i.e., the super El Niño and strong warming in the tropical Indian Ocean. (4) Significant differences in the circulation pattern were observed in August between the two years. The WPSH broke up in August 2016, with its western part being combined with the continental high and persistently dominating eastern China. The EASM suddenly became stronger, and dry conditions prevailed in the YRV. On the contrary, the EASM was weaker in August 1998 and the “Secondary Meiyu” took place in the YRV. The Madden–Julian Oscillation (MJO) was extremely active in August 2016 and stayed in western Pacific for 25 days. It triggered frequent tropical cyclone activities and further influenced the significant turning of tropical and subtropical circulations in August 2016. In contrast, the MJO was active over the tropical Indian Ocean in August 1998, conducive to the maintenance of a strong WPSH. Alongside the above oceanic factors and atmospheric circulation anomalies, the thermal effect of snow cover over the Qinghai–Tibetan Plateau from the preceding winter to spring in 2016 was much weaker than that in 1998. This may explain the relatively stronger EASM and more abundant precipitation in North China in 2016 than those in 1998.  相似文献   

17.
Guangzhou spring rainfall mainly exhibits interannual variation of Quasi-biannual and interdecadal variation of 30 yrs, and is in the period of weak rainfall at interdecadal time scale. SST anomalies (SSTA) of Nino3 are the strongest precursor of Guangzhou spring rainfall. They have significant positive correlation from previous November and persist stably to April. Nino3 SSTA in the previous winter affects Guangzhou spring rainfall through North Pacific subtropical high and low wind in spring. When Nino3 SSTA is positive in the previous winter, spring subtropical high is intense and westward, South China is located in the area of ascending airflow at the edge of the subtropical high, and water vapor transporting to South China is intensified by anticyclone circulation to the east of the Philippines. So Guangzhou spring rainfall is heavy. When Nino3 SSTA is negative, the subtropical high is weak and eastward, South China is far away from the subtropical high and is located in the area of descending airflow, and water vapor transporting to South China is weak because low-level cyclonic circulation controls areas to the east of the Philippines and north wind prevails in South China. So Guangzhou spring rainfall is weak and spring drought is resulted.  相似文献   

18.
The positive phase of the subtropical Indian Ocean dipole(SIOD) is one of the climatic modes in the subtropical southern Indian Ocean that influences the austral summer inter-annual rainfall variability in parts of southern Africa. This paper examines austral summer rain-bearing circulation types(CTs) in Africa south of the equator that are related to the positive SIOD and the dynamics through which specific rainfall regions in southern Africa can be influenced by this relationship. Four austral...  相似文献   

19.
In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although an El Ni~no event took place preceding each of the summer floods, significant differences between the two summer floods and the two El Ni~no events were identified. The 1997/98 El Ni~no is a conventional one with strongest warming in the central-eastern Pacific, whereas the 2009/10 event is an El Ni~no Modoki with strongest warming in the central Pacific. In this study, summer rainfall anomalies (SRA) in the two years were first compared based on the rainfall data at 160 stations in mainland China, and a significant difference in SRA was found. To understand the underlying mechanism for the difference, the atmospheric circulation systems, particularly the western North Pacific anticyclone (WNPAC), the western Pacific subtropical high (WPSH), and the low-level air flows, were compared in the two years by using the NCEP/NCAR reanalysis data. The results display that the WNPAC was stronger in 2010 than in 1998, along with a northwestward shift, causing weakened southwesterly from the Bay of Bengal to the South China Sea but intensified southerly in eastern China. This resulted in less water vapor transport from the tropical Indian Ocean and the South China Sea but more from the subtropical western Pacific to East Asia. Subsequently, the rainband in 2010 shifted northward. The difference in the WNPAC was caused by the anomalous ascending motion associated with the warming location in the two El Ni~no events. Furthermore, the role of tropical sea surface temperature (SST) in modulating these differences was investigated by conducting sensitivity experiments using GFDL AM2.1 (Geophysical Fluid Dynamics Laboratory Atmospheric Model). Two experiments were performed, one with the observed monthly SST and the other with June SST persisting through the whole summer. The results suggest that the model well reproduced the primary differences in the atmospheric circulation systems in the two years. It is found that the difference in El Ni~no events has shaped the rainfall patterns in the two years of 1998 and 2010. At last, the case of 2010 was compared with the composite of historical El Ni~no Modoki events, and the results indicate that the impact of El Ni~no Modoki varies from case to case and is more complicated than previously revealed.  相似文献   

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