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GEOGRAPHICAL RESEARCH >

2016 , Vol. 35 >Issue 1: 14 - 24

DOI: https://doi.org/10.11821/dlyj201601002

Orginal Article

Spatial pattern of decadal variation of summer precipitation in Eastern China: Comparison of observation and CESM control simulation

  • ZHENG Jingyun , 1 ,
  • WU Maowei 1, 2 ,
  • HAO Zhixin 1 ,
  • ZHANG Xuezhen , 1
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  • 1. Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
  • 2. University of Chinese Academy of Sciences, Beijing 100049, China

Received date: 2015-07-15

  Request revised date: 2015-11-26

  Online published: 2016-01-23

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《地理研究》编辑部
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Abstract

Using observed summer precipitation data from 389 sites for the period of 1961-2005, and a 650-year control simulation by the Community Earth System Model (CESM) with fixed pre-industrial external forcing, the dominant patterns of decadal variation of summer (June, July, August) precipitation over eastern China were analyzed with the EOF and Power Spectrum. The EOF analysis of both observed data and simulated data shows that the major patterns of decadal variation of summer precipitation over eastern China are a dipole pattern divided by the Huaihe River and a four zonal bands alternate with each other centered at South China, the Yangtze River Valley, North China Plain and Northeast China. Comparison between observation and simulation demonstrate that the CESM with the fixed external forcing reproduced well the above mentioned patterns and temporal alternations of phases of decadal variation of summer precipitation over eastern China during 1961 to 2005. This finding provides the knowledge for understanding the main causes of regional decadal precipitation anomalies and analyzing the influences of external forcing and internal variability on decadal variation of precipitation over China in future study.

Key words： summer precipitation; decadal variation; spatial pattern; simulation

Cite this article

ZHENG Jingyun , WU Maowei , HAO Zhixin , ZHANG Xuezhen . Spatial pattern of decadal variation of summer precipitation in Eastern China: Comparison of observation and CESM control simulation[J]. GEOGRAPHICAL RESEARCH, 2016 , 35(1) : 14 -24 . DOI: 10.11821/dlyj201601002

1 引言

年代际气候变化是影响月际及年际气候异常的背景,揭示年代际气候变化规律一直是气候变化研究的核心问题[1,2]。特别是面对当前全球增暖与复杂的气候变化态势,如近10余年的全球增暖停滞[3,4]、降水格局异常[5,6]、区域极端事件频发[7]等,以及社会各界对年代际气候预测的急切需求[8,9],更使其成为当前全球变化研究的热点。然而年代际气候变化既受气候系统内部变率调制,又受火山活动、太阳活动、人类活动等自然与人为外强迫变化的影响,特别是因全球多数地区的气象观测资料仅及百年,所以辨识年代际变化变化特征及其成因机制也一直是气候变化研究领域的难点。对未来数十年气候预测、情景预估具有重大意义[2,8-10]。
已有大量研究证明中国降水具有显著的年代际变化特征[11]。从内容看,这些研究逐步深入,从揭示中国夏季降水年代际变化格局,到分析其与大尺度环流转折的可能联系,再到探讨驱动机制等。其中于1990年代就有研究发现：中国夏季降水在1977-1979年发生了明显的年代际转折,导致长江流域降水增加,华北、华南降水减少[12,13]。此后又有研究发现：中国夏季降水在1990年代初也经历了一次显著的年代际转折,呈现出长江以南降水多、长江以北降水少的“跷跷板（Dipole）式”空间模态[14-17];并证明这种年代际转折现象与全球或大尺度的环流场变化有显著联系;如1970年代末的降水转折就伴随着副热带高压向西南的偏移、南亚高压增强、对流层冷却、副热带西风急流增强等大尺度的环流转折[18]。最近10年,研究者又对这一年代际变化格局的成因和驱动机制进行了大量探讨,结果表明：自20世纪70年代末以来,赤道东太平洋海表温度升高导致类El Niño模态加强[19,20];人为排放的温室气体增加导致印度洋增暖,使西太平洋副热带高压向西延伸、西风急流南移,以及人为排放气溶胶增加又导致亚洲海陆温差减小[21];这些因素造成东亚夏季风减弱,使得夏季输送至华北地区的水汽减少,从而导致华北降水减少、长江流域降水增加。在研究方法上,早期的研究主要采用主成分分析、旋转经验正交函数分解、聚类分析等方法[22,23]辨识降水变化的空间模态,并结合谱分析、突变检验等方法识别年代际降水转型的出现时间;近10年,主要采用数值模拟诊断分析方法[24,25],从不同视角对这一年代际变化特征的成因及机制进行了诊断。
已有研究多认为：中国东部降水的这种年代际变化格局可能是气候系统内部自然变率作用的结果,特别是与其对应的东亚夏季风（在1910年代之前也同样处于相对较弱时期）存在60~80年周期变率,因此1970年代末以来的东亚夏季风减弱趋势很可能是该周期的反映[26];而这种周期变率又与太平洋年代际振荡（PDO）、中纬度西风带扰动、北极涛动（AO）、北极海冰年代际异常等自然变率密切相关[27-32]。然而,也有研究认为：气候系统内部的自然变率虽然直接支配中国东部降水的年代际变化格局,但由温室气体增加驱动的全球增暖才是导致中国北方地区降水持续减少的重要因子[33];特别是环贝加尔湖地区持续显著增暖引起的蒙古国和中国华北地区对流层温度经向梯度和纬向风垂直切变减小和大气斜压性减弱,是导致华北地区夏季降水持续减少的关键因子[34]。还有研究通过对气候模拟的分析发现：增暖虽然在总体上导致包括亚洲季风区在内的全球季风降水增加,但其年代际变率的主控因子是Mega-ENSO和AMO等气候系统的内部变率[35,36];而中国东部降水变化的“南涝北旱”格局主要是自然变率作用所致,温室效应增强仅在一定程度上减弱了这种变化的强度[37]。这些结果差异说明对该问题的研究仍待深入。
为进一步分析这一问题,深入理解气候系统内部变率对中国东部夏季降水年代际变化的影响,本文采用固定外强迫条件下数值模拟试验结果与观测结果的对比分析思路。与以往关于中国东部夏季降水变化格局的研究不同,本文以美国国家大气研究中心（The National Center for Atmospheric Research,NCAR）新发展的通用地球系统模式（The Community Earth System Model,CESM）为工具,在固定外强迫条件下,开展了800年的连续积分试验（简称“控制试验”）。因为模拟试验的气候系统外强迫条件是固定的,所以该模拟结果给出的中国东部夏季降水变率由气候系统内部变率控制。通过模拟结果与观测数据的对比分析,不但可揭示气候系统内部变率导致的中国东部夏季降水年代际变化格局与观测结果的异同,也可为进一步区分气候系统外强迫变化和内部变率对降水异常的影响提供依据。

2 数据来源与研究方法

2.1 数据来源

（1）中国国家气象局提供的756个基本、基准地面气象观测站及自动站的逐月降水资料。因多数气象站建于20世纪50年代后期,且2008年又有较多站点因迁移、撤并等而导致数据不连续,故只选用1961-2005年东部地区（105°E以东）没有缺测、漏测的398个气象站（图1）数据。
Fig. 1 Location of observation stations and model grids

图1 观测站点位置及模式网格分布

（2）CESM控制试验模拟的全球月平均降水资料。CESM模式从通用气候系统模式（The Community Climate System Model）发展而来,由大气模块（the Community Atmosphere Model,CAM）、海洋模块（Parallel Ocean Program,POP）、陆地模块（the Community Land Model,CLM）、海冰模块（the Sea-Ice Component,CICE）、陆冰模块（Land-Ice Component）和耦合器（Coupler）组成,被认为是世界上最先进的模式之一[38];已有评估表明该模式对亚洲季风区降水变化有较好的模拟能力,可模拟出中国降水多年平均的主要空间模态[39]。本文的模拟试验物理过程配置如下：CAM4大气模块、POP2海洋模块,CLM4陆地模块和CICE4海冰模块;其中海洋模块的空间分辨率约为1.0°×1.0°,大气和陆地模块的空间分辨率为2.5°×1.9°,未启用陆冰模块以及陆地模块中的碳、氮循环过程。模拟试验在固定外强迫下进行,其中太阳总辐射量（TSI）为1360.89 W/m2,温室气体CO2、CH4、N2O的体积浓度分别为2.847×10-4、7.916×10-7、2.7568×10-7,气溶胶浓度和土地利用为NCAR给定的1850年的强迫场。试验的总长度为800年,其中1~150年为模式起转（spin-up）时段,所以用于分析的实际数据长度为650年（即151~800模式年）。图1给出其中用于分析的空间范围和网格。由于该试验不含任何外强迫变化,因而这一结果只反映气候系统的内部变率。

2.2 研究方法

由于关注年代际尺度上的变率,因此先利用观测及模拟的逐月的降水量,计算逐年夏季（6-8月）降水量,并将其转换成降水距平百分率;然后借鉴Lei等采用的方法[40],分别对观测和模拟的逐年夏季降水距平百分率进行11年滑动平均,以滤除10年尺度以下的高频信号,保留10年尺度以上的低频信号用于夏季降水的年代际变化特征分析,包括利用经验正交函数分解（EOF）的方法[41-43]提取主导空间模态,利用功率谱分析[44]辨识时间系数的年代际周期特征;最后采用滑动相关分析方法,进行模拟与观测结果的时空变化特征对比。

3 结果分析

3.1 观测结果

对1961-2005年东部地区398个站夏季（6-8月）降水观测资料的EOF分析（表1）显示：在前10个主分量（累计方差解释量达96.1%）中,前2个主分量的解释方差量分别为38.8%和30.9%,累计达69.7%;而通过North独立性检验的第3~6个主分量解释方差分别只有12.1%、6.0%、2.3%和1.7%;第7及以后的主分量则未通过独立性检验。这说明过去50年中国东部地区夏季降水的年代际变化主要由前两个模态控制（图2）。
Tab. 1 The variances explained by the leading ten EOFs of the observed decadal variations of summer precipitation over eastern China during 1961-2005

表1 1961-2005年中国东部夏季降水年代际变化前10个EOF的解释方差量

主分量 EOF1 EOF2 EOF3 EOF4 EOF5 EOF6 EOF7 EOF8 EOF9 EOF10
解释方差（%） 38.8* 30.9* 12.1* 6.0* 2.3* 1.7* 1.2 1.1 1.0 0.7

注：*表示通过了North独立性检验。

Fig. 2 The leading two EOFs and corresponding PCs derived from the observed decadal variation of summer precipitation over eastern China during 1961-2005

图2 1961-2005年观测资料揭示的中国东部夏季降水年代际变化的前两个空间模态及其时间系数

图2显示：中国东部夏季降水年代际变化的第一个空间模态（EOF1）大致呈南北反相分布。其中淮河流域及其以南（中心位于江南）地区变化趋势一致,北方的秦岭—黄土高原—华北平原（中心位于华北平原）变化趋势则与南方地区相反,仅内蒙及东北的部分地区变化趋势与南方地区一致。该模态的时间系数在1986年左右处于极大值,说明其代表的“南旱北涝”格局在该时刻最为显著;1986年后开始迅速减小,反映了南方降水逐渐增加,北方的秦岭—黄土高原—华北平原降水逐渐减少的变化趋势;于1990年发生的位相转变表示中国东部夏季降水格局由“南少北多”变为“南多北少”;之后进入负位相,并到1997年达到极小值,说明该时期南方降水相对偏多,而秦岭—黄土高原—华北平原地区相对偏少。可见EOF1表征出了中国东部夏季降水在1990年代初期经历的年代际变化[14-17]。
第二个空间模态（EOF2）呈现出由南到北的多带相间分布格局。其中长江流域与东北地区夏季降水变化趋势一致,而华南地区和华北平原则与之相反。该模态的时间系数在1978年以前处于正位相,极大值位于1971年左右,表明该时期华北和华南地区降水偏多,而长江流域和东北地区降水偏少;而1979年之后进入进入负位相,并于1986年达到极小值,反映出该时期长江流域降水显著增加,而华北和华南地区降水减少;1986年后逐渐回升,但直到2000年左右回到零值附近,说明该降水型虽然又向着相反的方向变化,但仍未转回1960年代的华南地区和华北平原相对多雨、长江流域和东北地区相对少雨格局。因此EOF2主要表示了中国东部夏季降水在1970年代末的显著转折[12,13]。这一结果与前人利用观测资料分析得到的过去50年中国东部夏季降水两次主要年代际转折的时间非常吻合。

3.2 模拟结果

对CESM模式控制试验模拟的650年中国东部夏季降水数据的EOF分析（表2）显示：其前10个主分量的解释方差量累计为77.9%。其中前3个主分量的解释方差量分别为24.7%、14.8%、9.0%;第4和第5个主分量解释方差量虽与第3主分量相差并不大,但未通过North独立性检验,说明其与前3个主分量存在相关性;这5个主分量的累计方差贡献共达62.1%。而第6和第7个主分量虽通过North独立性检验,但其解释方差量较小,第8~10个主分量也未通过North独立性检验。这说明前5个主分量足以代表该模拟结果的中国夏季降水变化主导空间型。
Tab. 2 The variances explained by the leading ten EOFs of decadal variation of summer precipitation over eastern China in the 650-year simulation of CESM

表2 CESM模式控制试验模拟的中国东部夏季降水变化前10个主分量的解释方差量

主分量 EOF1 EOF2 EOF3 EOF4 EOF5 EOF6 EOF7 EOF8 EOF9 EOF10
解释方差（%） 24.7* 14.8* 9.0* 6.9 6.7 4.4* 3.6* 3.0 2.6 2.2

注：*表示通过了North独立性检验。

图3给出了CESM模拟的中国夏季降水年代际变化前5个主分量（累计方差贡献达62.1%）的空间型及其对应的时间系数变化功率谱分析结果。从中可见,第1个空间模态（EOF1）为显著的南北反相模态,分界线为秦岭—淮河线。第2个空间模态（EOF2）同样为南北反相的分布,但分界线较第1模态更为偏南（约27°N附近）,且内蒙及东北也有部分地区变化趋势与南方地区一致。第3个空间模态（EOF3）为自南到北的多带相间格局,且江南与东北变化趋势一致,华北和华南南部一致且与江南和东北变化趋势相反。第4个空间模态（EOF4）除长江以南外的其他地区降水变化格局与EOF2相似,因而其在统计上没有独立性。第5个空间模态（EOF5）在统计上也没有独立性,其总体格局与EOF3相似,只是范围大小略有不同。这表明：CESM模式控制试验模拟的中国东部夏季降水年代际变化的空间型亦以南北反相和由南到北的多带相间反相变化为主要特征。功率谱分析显示,各模态时间系数变化的显著周期为：第1模态,40年和29年,以40年最为显著;第2模态为50年和40年,亦以40年最为显著;第3模态为33年和29年,以33年最为显著;第4模态为25年和22年,以25年最为显著;第5模态为准33年;说明这些空间格局存在准40年、33年和25年的年代际变化特征。
Fig. 3 The leading five EOFs and power spectrums (dashed line indicates a significant level of 95%) of the corresponding PCs for decadal variation of summer precipitation over eastern China in control simulation of CESM

图3 CESM模式控制试验模拟的中国东部夏季降水年代际变化前5个主分量的空间模态及其时间系数的功率谱（虚线为95%显著性水平检验线）

3.3 对比分析

对比上述观测和模拟结果可以看出：虽然观测和CESM的控制试验模拟均反映出中国东部夏季降水年代际变化主导空间型是南北反相和由南到北的多带相间反相变化,但二者的主分量并不一一对应,这主要是由于观测数据时间跨度短、模拟结果的时间跨度长造成的。为此,将模拟结果中每一个连续的45年时段都单独提取出来,与观测结果作进一步对比分析。具体步骤是,以45年（即观测数据的覆盖长度）为单位时段,采用滑动方法先对模拟结果中每个连续45年时段的数据进行EOF分析,然后将其前两个主分量的空间型和时间系数分别与观测数据中前两个主分量的空间型和时间系数进行相关分析;以辨识模拟结果中是否存在与观测结果相似的时段。如果观测和模拟的EOF1、PC1和EOF2、PC2均高度相关,且对应的EOF和PC的相关系数同号,则记该时段为“相似时段”,然后再比较每个“相似时段”与观测时段之间的前两个EOF及其对应的时间变化的相关系数。
因模拟试验的结果总长度为650年,故共计可以提取出606个长度为45年的时段。通过对每个45年时段的EOF分析及其与观测结果的相关分析,结果显示：在0.01的显著性水平下,模拟结果中有129个与观测结果相似的时段;其中显著性水平达0.0001的有28个。然而这些相似时段的两两之间可能存在重叠年份,因而并不独立。其中显著性水平超过0.0001的28个相似时段主要集中出现在：333~385模式年、414~460模式年、515~567模式年和596~646模式年。为此,从每个时段中分别选取一个与观测结果相关系数（表3）最高的45年时段作为代表,与观测结果进行对比。结果显示,在选取出的4个45年时段中,模拟与观测结果之间的空间型相关系数绝对值最高达0.73,最低为0.32;时间系数的相关系数绝对值最高者达0.95,最低也达0.66。
Tab. 3 Spatial and temporal correlations of the leading two EOFs of the four 45-year periods in simulation with their counterparts in observation

表3 模式模拟的4个45年时段与观测时段之间的前2个EOF的相关系数

相似时段
（模式年）		 相关系数
EOF1 PC1 EOF2 PC2
时段1（336~380） 0.65 0.72 -0.43 -0.91
时段2（415~459） -0.53 -0.72 -0.32 -0.66
时段3（519~563） -0.73 -0.81 0.32 0.95
时段4（599~643） -0.54 -0.80 -0.46 -0.80
进一步对比（表4）还发现：这4个相似时段降水年代际变化的前两个EOF的累计方差解释量均达到70%左右,即与观测结果极为接近,说明这4个时段的年代际降水变化特征是由前两个主分量主导的。图4给出了这4个时段的前两个EOF空间型及时间系数变化。从图中可以看出,第1主分量空间型均呈现出南北反相的特征,即在淮河流域的南北各存在一个显著的降水变率中心,并且时间系数发生位相转变的时间点（第27~30年）也与观测结果所揭示的在1990年（第30年）出现位相转变的时间非常一致。其中时段1与观测结果的空间模态（EOF1,图2）和时间系数变化趋势均相同,时间系数（PC1）位相的转折点与观测的PC1亦极为一致;时段2~4的空间模态（EOF1）和时间系数变化趋势均相反,且时间系数的转折点也与观测的PC1相同;因此这4个时段反映的中国东部夏季降水变化格局是相同的,均在第30年前后由“南少北多”转为“南多北少”。
Tab. 4 The variances explained by the leading two EOFs in the four 45-year periods in simulation compared with those in observation(%)

表4 观测与4个模式模拟时段的前两个主成分解释方差量对比（%）

空间模态 观测 相似时段（模式年）
时段1（336~380） 时段2（415~459） 时段3（519~563） 时段4（599~643）
EOF1 38.8 45.5 35.9 56.4 47.6
EOF2 30.9 23.2 27.4 19.3 23.7
Total 69.7 68.7 63.3 75.7 71.3
Fig. 4 The leading two EOFs and PCs of decadal variation of summer precipitation over eastern China in the four 45-year periods from 650-year simulation

图4 模式模拟的4个连续45年时段夏季降水年代际变化的前两个EOF及时间系数

第2主分量的空间型则呈现南北多纬向雨带相间分布的特征,且其时间系数也分别在第19年（对应观测的1979年）和第39年（对应观测的1999年）存在2次转折。其中时段3的第2空间模态与观测结果的EOF2（图2）均为自南向北的“+ - + -”格局;其时间系数（PC2）变化转折点与观测的PC2亦极为一致;时段1、2、4则为与观测EOF2相反的“- + - +”格局,但其时间系数变化趋势也与观测的PC变化趋势相反。说明这些时段与观测时段一样,均在第19年前后由华南地区和华北平原相对多雨、长江流域和东北地区相对少雨转为华南地区和华北平原相对少雨、长江流域和东北地区相对多雨,而后又在第39年再次向相反的方向转变。
上述对比证明：在CESM模式控制试验的650年结果中,存在多个与1961-2005年观测到的中国东部夏季降水年代际变化特征基本一致的时段;说明在没有任何外强迫变化下,仅通过气候系统的内部变率驱动,也可模拟出中国东部夏季降水年代际变化的空间格局及其位相转折特征。这一结果同先前一些研究[27-32,37]得到的中国东部20世纪后期“南涝北旱”主要受自然变率影响的认识一致。
然而,值得注意的是,在模拟试验的650年中,中国东部夏季降水年代际变化的前5个主要空间模态与观测的两个主导模态虽然不完全相同,但在45年“片段”中,却有多个时段与观测时段的前两个主导模态高度相似。对此本文认为,在45年的片段中占据主导地位的两个模态应是650年中前5个主要模态周期变化的叠加结果。因为：① 模拟试验显示,前5个主要模态分别存在25年、33年、40年左右的周期特征,4个相似时段也近似以80~100年的周期重现;② 前5个主要模态解释方差量总和与45年的片段中两个主导模态的解释方差量之和基本相当。此外,虽然这5个主要模态的空间型与45年的片段中两个主导模态虽不完全相同,但基本都呈现类似的南北反相或者多带相间分布格局。不过由于这5个主要模态并非严格的周期重现,因此其叠加出来的两个主导模态会或多或少出现时间位相的错位;从而导致了模拟与观测间的两个主导模态的时间变化虽具有极为类似的年代际变化趋势,但在一些具体转折点并不完全一致。

4 结论与讨论

利用观测资料与CESM控制试验模拟结果分析了中国东部夏季降水的年代际变化格局,通过二者结果的对比发现：
（1）1961-2005年,中国东部夏季降水的年代际变化的主导空间模态呈“南北（以淮河流域为界）反相”和由南到北的“多带相间反相分布（长江流域、东北同相但与华南、华北反相）”格局;其中南北反相型在1990年前后出现位相转变,而多带相间反相分布型则分别在1979年和1999年发生两次位相转折;与前人利用观测资料分析得到的过去50年中国东部夏季降水两次主要年代际转折的时间非常吻合;这导致了1970年代末以来中国东部出现显著的北旱南涝特征。
（2）在固定外边界条件驱动下,CESM的650年控制试验模拟结果中,也存在多个与1961-2005年中国东部夏季降水年代际变化特征一致的时段;证明在没有任何外强迫变化的情况下,仅通过气候系统的内部变率驱动,也可使中国东部的夏季降水出现与观测到的年代际变化主导空间型和相应的时间位相转折变化一致的特征。因而可以认为控制1961年以来中国东部夏季降水年代际变化的直接驱动力应是气候系统的内部变率。
然而,气候系统的内部变率同样也受外驱动变化的影响。因而,气候系统内部的自然变率虽然可直接主控中国东部降水年代际变化的格局,但外驱动如何影响气候系统的内部变率,特别是外驱动变化如何通过气候系统内部变率的调制作用导致中国旱涝格局发生变化仍是一个需要深入研究的问题。而要深入研究这一问题,不但需要对更长时段的资料分析,包括利用高分辨率的代用资料进行降水变化格局与外驱动异常的对比分析,而且还需要利用气候模式进行各个外强迫因子及其组合变化驱动的长时段气候变化模拟试验,并通过对这两种手段研究结果的综合对比去诊断外强迫变化驱动气候系统内部变率变化进而导致区域气候变化的机制。这正是国际过去全球变化计划关注的核心科学问题之一[45],同时也是中国长期气候变化研究的薄弱环节,亟待加强,并需要历史气候与现代气候变化研究者的交叉与合作。
最后还需指出的是：因受观测资料时间长度仅45年的限制,所以本文辨识的降水年代际变化特征可能存在因资料短缺而导致的误差。此外,尽管CESM被认为是世界上最先进的模式之一,对中国东部季风降水的主要空间模态及其变化有较好的模拟能力,但其对降水量绝对值、年际变率等的模拟仍存在一定误差,这也是大多数气候模式共同的弱点。这两点不足可能会导致结论存在不确定性,需要在今后研究中予以进一步的证实。

The authors have declared that no competing interests exist.

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黄荣辉, 陈际龙, 刘永. 我国东部夏季降水异常主模态的年代际变化及其与东亚水汽输送的关系. 大气科学, 2011, 35(4): 589-606.本文利用1958～2000年ERA-40再分析每日资料和我国516台站降水资料以及EOF方法, 分析了我国东部季风区夏季降水异常主模态的年代际变化特征及其与东亚上空水汽输送通量时空变化的关系。分析结果表明了我国东部季风区夏季降水的时空变化存在两种主模态: 第1主模态不仅显示出明显的准两年周期振荡的年际变化特征且也有明显的年代际变化, 在空间上具有经向三极子型分布; 第2主模态显示出明显的年代际变化特征, 且在空间上具有经向偶极子型分布。这表明了这两主模态有明显的年代际变化, 在1958～1977年期间我国东部夏季降水异常分布为从南到北 “＋－＋” 经向三极子型分布, 而在1978～1992年期间降水异常出现了与1958～1977年相反的分布, 为从南到北 “－＋－” 经向三极子型分布。然而, 在1993～1998年期间, 由于第2主模态的作用增大, 我国东部夏季降水异常为从南到北经向三极子型与 “＋－” 偶极子型模态的结合, 这使华南夏季降水明显增加。并且, 分析结果还表明: 这两主模态的年代际变化与东亚上空夏季水汽输送通量的时空变化密切相关, 它不仅与东亚和西北太平洋上空似如东亚/太平洋型 (EAP型) 遥相关波列分布的夏季水汽输送通量异常年代际变化有关, 而且与欧亚上空中高纬度西风带似如欧亚型 (EU型) 遥相关波列的夏季水汽输送通量异常年代际变化密切相关。

DOI

[Huang Ronghui, Chen Jilong, Liu Yong.Interdecadal variation of the leading modes of summertime precipitation anomalies over Eastern China and its association with water vapor transport over East Asia. Chinese Journal of Atmospheric Sciences, 2011, 35(4): 589-606.]

[18]
Huang Ronghui, Liu Yong, Feng Tao.Interdecadal change of summer precipitation over Eastern China around the late-1990s and associated circulation anomalies, internal dynamical causes. Chinese Science Bulletin, 2013, 58(12): 1339-1349.Observational study indicated that the summer precipitation over Eastern China experienced a notable interdecadal change around the late-1990s. Accompanying this interdecadal change, the dominant mode of anomalous precipitation switched from a meridional triple pattern to a dipole pattern, showing a "south-flood-north-drought" structure (with the exception of the Yangtze River Valley). This interdecadal change of summer precipitation over Eastern China was associated with circulation anomalies in the middle/upper troposphere over East Asia, such as changes in winds and corresponding divergence, vertical motion and moisture transportation (divergence), which all exhibit remarkable meridional dipole structures. Furthermore, on the internal dynamic and thermodynamic aspects, the present study investigated the influence of the midtroposphere zonal and meridional flow changes over East Asia on the interdecadal change around the late-1990s. Results suggested that, during 1999-2010, the East Asia subtropical westerly jet weakened and shifted poleward, forming a meridional dipole feature in anomalous zonal flow. This anomalous zonal flow, on one hand, induced changes in three teleconnection patterns over the Eurasian continent, namely the "Silk Road" pattern along the subtropical upper troposphere westerly jet, the East Asia/Pacific (EAP) pattern along the East Asian coast, and the Eurasia (EU) pattern along the polar jet; on the other hand, it brought about cold advection over Northern China, and warm advection over Southern China in the mid-troposphere. Through these two ways, the changes in the zonal flow induced descent over Northern China and ascent over Southern China, which resulted in the anomalous "south-flood-north-drought" feature of the summer precipitation over Eastern China during 1999-2010.

DOI

[19]
Li Hongmei, Dai Aiguo, Zhou Tianjun.Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950-2000. Climate Dynamics, 2010, 34(4): 501-514.The East Asian summer monsoon (EASM) circulation and summer rainfall over East China have experienced large decadal changes during the latter half of the 20th century. To investigate the potential causes behind these changes, a series of simulations using the national center for atmospheric research (NCAR) community atmospheric model version 3 (CAM3) and the geophysical fluid dynamics laboratory (GFDL) atmospheric model version 2.1 (AM2.1) are analyzed. These simulations are forced separately with different historical forcing, namely tropical sea surface temperature (SSTs), global SSTs, greenhouse gases plus aerosols, and a combination of global SSTs and greenhouse gases plus aerosols. This study focuses on the relative roles of these individual forcings in causing the observed monsoon and rainfall changes over East Asia during 1950–2000. The simulations from both models show that the SST forcing, primarily from the Tropics, is able to induce most of the observed weakening of the EASM circulation, while the greenhouse gas plus (direct) aerosol forcing increases the land-sea thermal contrast and thus enhances the EASM circulation. The results suggest that the recent warming in the Tropics, especially the warming associated with the tropical interdecadal variability centered over the central and eastern Pacific, is a primary cause for the weakening of the EASM since the late 1970s. However, a realistic simulation of the relatively small-scale rainfall change pattern over East China remains a challenge for the global models.

DOI

[20]
Zhou Tianjun, Gong Daoyi, Li Jian, et al.Detecting and understanding the multi-decadal variability of the East Asian Summer Monsoon: Recent progress and state of affairs. Meteorologische Zeitschrift, 2009, 18(4): 455-467.East Asia is dominated by a typical monsoon climate. The East Asian summer monsoon (EASM) exhibits considerable variability on a wide range of time scales during the 20 century. A substantial portion is the multi-decadal variability. Over the recent decades, the EASM has been weakening from the end of the 1970s which results in a "southern China flood and northern China drought" rainfall pattern. Understanding the mechanisms responsible for the weakening tendency has been a challenge for climate research community. Examinations on the long-term change of the EASM during the 20 century find no significant trends, indicating the pronounced weakening tendency of the EASM in recent decades is unprecedented. After documenting the prominent features of the interdecadal climate transition, a review is presented in this paper on the proposed explanations to the observed changes. The proposed factors include the Indian Ocean and far western Pacific warming, the tropical central-eastern Pacific warming, the weakening sensible heat source over the Tibetan Plateau, and the aerosol forcing, as well as internal variability. While parts of the monsoon circulation changes can be explained in terms of the proposed mechanisms, it is still beyond the scope of our current knowledge to present a complete picture. Much remains to be learned about the mechanisms that produce such multi-decadal changes in the EASM, but it seems still unclear whether human activities and global warming are playing significant roles. German Ostasien wird von einem typischen Monsunklima beherrscht. Der ostasiatische Sommermonsun (EASM) zeigt w01hrend des 20. Jahrhunderts eine erhebliche Variabilit01t über ein breites Spektrum von Zeitskalen hinweg. Ein gr0208erer Teil davon ist multidekadische Variabilit01t. Seit dem Ende der 1970er Jahre hat sich der EASM abgeschw01cht, was zu dem "Südchina-Flut - Nordchina-Dürre" Muster geführt hat. Das Verst01ndnis für die Ursachen dieser Abschw01chungstendenz stellt eine Herausforderung für die Klimatologie dar. Untersuchungen der langfristigen 02nderungen des EASM w01hrend des gesamten 20. Jahrhunderts zeigen keine signifikanten Trends, was bedeutet, dass die 02nderung in den letzten Jahrzehnten ohne Beispiel ist. Nach einer Dokumentation der wichtigsten Ph01nomene dieser interdekalen Klima01nderung bietet die vorliegende Arbeit einen 05berblick über die m02glichen Erkl01rungen für die beobachteten 02nderungen. Diese beinhalten unter anderem eine Erw01rmung des mittleren und 02stlichen Pazifiks, eine Abschw01chung der w01rmequelle über dem tibetischen Plateau, einen Antrieb durch Aerosol wie auch interne Variabilit01ten. w01hrend Teile der 02nderung der Monsunzirkulation hierdurch erkl01rt werden k02nnen, liegt eine vollst01ndige Erkl01rung des Ph01nomens noch jenseits unseres derzeitigen Wissensstands. Es muss noch viel über die Mechanismen verstanden werden, die solche interdekalen 02nderungen des EASM hervorrufen, wobei es noch unklar ist ob menschliche Aktivit01ten und die globale Erw01rmung eine signifikante Rolle spielen.

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[21]
Wang Tao, Wang Huijun, Ottera O H, et al.Anthropogenic agent implicated as a prime driver of shift in precipitation in eastern China in the late 1970s. Atmospheric Chemistry Physics, 2013, 13(24): 12433-12450.

[22]
王艳姣, 闫峰. 1960-2010年中国降水区域分异及年代际变化特征. 地理科学进展, 2014, 33(10): 1354-1363.利用1960-2010 年中国1840 个台站年降水量数据,采用经验正交函数(EOF)和旋转经验正交函数分解方法(REOF)对降水进行分区,并对各区降水的变化特征进行了研究。结果表明:基于多站点资料结合REOF方法实现的降水分区与中国降水实际区域分异特征比较符合,并与中国气候区划相一致。中国各区降水变化特征分析表明,东部各区降水在20 世纪70 年代末、80 年代末-90 年代初和21 世纪初发生雨带的南北移动过程,其中夏季雨带的移动主要受东亚夏季风和大气环流年代际变化的影响。西北地区降水以1985/1986 年为突变年,西北西部地区降水由前期偏少转为偏多,主要与来自阿拉伯海和里海异常偏多的水汽输送有关;西北东部地区降水由前期偏多转为偏少,主要与季风的年代际减弱有关。东北地区降水在80 年代初由前期接近正常转为偏多,90 年代末降水由前期偏多转为偏少,主要与季风和西北太平洋水汽输送的年代际变化相关。西南部各区降水阶段性变化明显,2000 年以前西南东北部地区降水与西部地区基本呈反向变化,主要受青藏高原地形、东亚季风和副热带高压等因素的影响,降水阶段性变化明显、成因复杂。

DOI

[Wang Yanjiao, Yan Feng.Regional differentiation and decadal change of precipitation in China in 1960-2010. Progress in Geography, 2014, 33(10): 1354-1363.]

[23]
吕俊梅, 琚建华, 江建民. 近一百年中国东部区域降水的年代际跃变. 大气科学, 2009, 33(3): 524-536.采用均生函数方法对1900～1950年中国东部测站降水资料进行补插, 通过与英国Climate Research Unit (CRU) 的网格点降水资料以及王绍武等 (2000) 重建的降水资料的对比分析, 构造1900～2006年中国东部华北、 长江中下游和华南地区的月平均降水指数序列, 并用一阶矩突变扫描式t检验对这三个区域降水的多时间尺度跃变特征进行分析。结果表明, 最近一百多年来长江中下游降水发生了5次年代际尺度的跃变, 华北以及华南的降水均发生了4次年代际尺度的跃变。各区降水同时在20世纪20年代初期、 40年代中期、 60年代中期以及70年代中期发生跃变。具体而言, 20年代初期长江中下游和华南的降水发生年代际减少, 而此时华北降水年代际增加; 40年代中期, 三个地区的降水都同时增加; 60年代中期, 华北降水减少, 相反地长江中下游和华南的降水发生年代际增加; 70年代中期, 华南和华北地区的降水出现年代际减少, 而长江中下游地区的降水在80年代初发生年代际增加。研究还表明, 降水跃变发生的时间尺度范围可以为我们预测跃变发生以后降水气候平均态的持续时间提供参考。

DOI

[Lv Junmei, Ju Jianhua, Jiang Jianmin.Interdecadal regime shifts of regional precipitation over eastern China during the last 100 years. Chinese Journal of Atmospheric Sciences, 2009, 33(3): 524-526.]

[24]
曾刚, 孙照渤, 王维强, 等. 东亚夏季风年代际变化: 基于全球观测海表温度驱动NCAR Cam3的模拟分析. 气候与环境研究, 2007, 12(2): 211-224.利用1950-1999年逐月全球观测海表温度驱动的NCARCam^3全球大气环流模式 50年模拟结果及1958-1999年ECMWF再分析资料，通过定义东亚夏季风指数，对比分析了东亚夏季风的年代际变化及其对应的大气环流特征，初步探 讨了20世纪70年代末东亚夏季风年代际减弱的可能机制。结果表明：模拟的东亚夏季风具有很明显的年代际变化，并在20世纪70年代末发生了突变，由强夏 季风转为弱夏季风，大气环流也相应发生了明显变化。在强夏季风时期，500hPa距平高度场上，在亚太地区从低纬度到高纬度为负、正、负距平分布，呈现出 一个西南东北向的波列；850hPa距平风场上，在孟加拉湾及南海附近为异常反气旋，在西北太平洋区域则为强大的异常气旋，日本北部有一异常反气旋存在。 西北太平洋副热带高压加强、南压、西伸。在垂直经向环流上，东亚Hadley环流减弱，对流层低层出现异常南风，东亚夏季风加强。在弱夏季风时期，大气环 流变化则基本相反。通过对模拟的东亚夏季风与观测海温关系的探讨，发现20世纪70年代末东亚夏季风年代际减弱可能与北印度洋和南海附近海温年代际增暖并 导致孟加拉湾、南海及日本附近产生异常气旋有关。

DOI

[Zeng Gang, Sun Zhaobo, Wang Weichyung, et al.Interdecadal variation of east Asian summer: Monsoon simulated by NCAR Cam3 driven by global SSTs. Climatic and Environmental Research, 2007, 12(2): 211-224.]

[25]
陈红, 薛峰. 东亚夏季风和中国东部夏季降水年代际变化的模拟. 大气科学, 2013, 37(5): 1143-1153.利用中国科学院大气物理研究所发展的第四代大气环流模式模拟了1970年代末东亚夏季风和相关的中国东部夏季降水年代际变化。结果表明,在给定的观测海温强迫下,模式能模拟出东亚夏季风的年代际减弱及 相关的环流场变化,包括东亚沿海的偏北风异常以及西太平洋副高的形态变化,模式还较好再现了中国东部夏季降水的雨型变化,即长江流域降水偏多,而华北和华南偏少,但位置略偏南。基于奇异值分解(SVD)的分析表明,热带海洋变暖是这次东亚夏季风的年代际减弱的主要因素,这与太平洋年代际振荡(PDO)在1970年代末期的位相转变有关。此外,模式还较好模拟了长江流域的变冷趋势,进而减弱了海陆温差,使东亚夏季风减弱。

DOI

[Chen Hong, Xue Feng.Numerical simulation of decadal variations in the east Asian summer monsoon and summer rainfall in eastern China. Chinese Journal of Atmospheric Sciences, 2013, 37(5): 1143-1153.]

[26]
Ding Yihu, Ren Guoyu, Zhao Zongci, et al.Detection, causes and projection of climate change over China: An overview of recent progress. Advances in Atmospheric Sciences, 24(6): 954-971.This article summarizes the main results and findings of studies conducted by Chinese scientists in the past five years.It is shown that observed climate change in China bears a strong similarity with the global average.The country-averaged annual mean surface air temperature has increased by 1.1℃over the past 50 years and 0.5-0.8℃ over the past 100 years.slightly higher than the global temperature increase for the same periods.Northern China and winter have experienced the greatest increases in surface air temperature.Although no significant trend has been found in country-averaged annual precipitation,interdecadal variability and obvious trends on regional scales are detectable,with northwestern China and the mid and lower Yangtze River basin having undergone an obvious increase,and North China a severe drought.Some analyses show that frequency and magnitude of extreme weather and climate events have also undergone significant changes in the past 50 years or so.Studies of the causes of regional climate change through the use of climate models and consideration of various forcings,show that the warming of the last 50 years could possibly be attributed to an increased atmospheric concentration of greenhouse gases,while the temperature change of the first half of the 20th century may be due to solar activity,volcanic eruptions and sea surface temperature change.A significant decline in sunshine duration and solar radiation at the surface in eastern China has been attributed to the increased emission of pollutants.Projections of future climate by models of the NCC(National Climate Center,China Meteorological Administration)and the IAP(Institute of Atmospheric Physics,Chinese Academy of Sciences),as well as 40 modeis developed overseas,indicate a potential significant warming in China in the 21st century,with the largest warming set to occur in winter months and in northern China.Under varied emission scenarios,the country-averaged annual mean temperature is projected to increase by 1.5-2.1℃ by 2020,2.3-3.3℃ by 2050,and by 3.9-6.0℃ by 2100,in comparison to the 30-year average of 1961-1990.Most models project a 10%-12%increase in annual precipitation in China by 2100,with the trend being particularly evident in Northeast and Northwest China,but with parts of central China probably undergoing a drying trend.Large uncertainty exists in the projection of precipitation,and further studies are needed.Furthermore,anthropogenic climate change will probably lead to a weaker winter monsoon and a stronger summer monsoon in eastern Asia.

DOI

[27]
周连童, 黄荣辉. 关于我国夏季气候年代际变化特征及其可能成因的研究. 气候与环境研究, 2003, 8(3): 274-290.利用我国160个台站1951～2000年夏季(6～8月)降水和气温观测资料,以及NCEP/NCAR海温、风场和水汽的再分析资料,分析了我国夏季风 降水和气温的年代际变化特征及其可能成因.分析结果表明,我国夏季降水有明显的年代际变化,在1976年前后发生了一次明显的气候跃变,从1977年到 2000年夏季长江流域的降水明显增加,而华北地区和黄河流域夏季降水明显减少,出现了严重干旱.分析结果还表明,我国西北地区降水的振荡位相要超前于华 北地区降水振荡位相5～8年,华北地区气候年代际时间尺度变化是从1977年起降水减少,气温上升;但西北地区从20世纪70年代开始,则温度升高,降水 增多.此外,分析结果也表明我国气温同样有年代际变化,但不如降水年代际变化明显.作者还从热带太平洋SST(海面温度)的年代际变化及其对中印半岛和东 亚上空水汽输送的影响,分析了上述我国气候年代际变化的可能成因.分析结果表明,热带中东太平洋的SST也有明显的年代际变化,从1976年以后热带中东 太平洋海水明显增暖,出现了明显的"类似El Nino型"的SST距平分布,呈现出"年代际的El Nino现象".这种海温异常分布减弱了亚洲夏季风,从而减弱了从热带太平洋、中国南海和孟加拉湾向东亚的水汽输送,造成水汽输送在长江流域辐合,使到达 华北地区的水汽大大减弱,因此引起长江流域降水明显增加,而华北地区明显减少,出现了持续性严重干旱.

DOI

[Zhou Liantong, Huang Ronghui.Research on the characteristics of inter-decadal variability of summer climate in China and its possible cause. Climatic and Environmental Research, 2003, 8(3): 274-290.]

[28]
张庆云, 吕俊梅, 杨莲梅, 等. 夏季中国降水型的年代际变化与大气内部动力过程及外强迫因子关系. 大气科学, 2007, 31(6): 1290-1300.根据中国160站月平均降水、NCEP/NCAR的再分析资料以及英国气象局哈德莱中心1900～1999年全球1°×1°格点月平均海表温度距平资料，利用物理量诊断、EOF分析等方法，探讨东亚季风区大气环流内部动力过程与大气外强迫因子（海温）年代际变化及对中国夏季降水型的影响。分析发现，中国东部地区、西北地区夏季降水型有各自不同的年代际变化趋势；中国东部夏季降水型及东亚夏季风环流年代际变化趋势与大气外强迫因子北太平洋中纬度海温年代际变化（PDO）关系密切；中国西北地区夏季降水年代际变化与大气内部动力过程中纬度西风带扰动动能年代际减弱有关。

DOI

[Zhang Qingyun, Lv Junmei, Yang Lianmei, et al.The inter-decadal variation of precipitation pattern over China during summer and its relationship with the atmospheric internal dynamic processes and extra-forcing factors. Chinese Journal of Atmospheric Sciences, 2007, 31(6): 1290-1300.]

[29]
白爱娟, 翟盘茂. 中国近百年气候变化的自然原因讨论. 气象科学, 2007, 27(5): 584-590.本文分析了近百年来中国气候变化的概况，讨论了影响中国气候变化的自然因素大气环流和海温，此外还叙述了有关大气气溶胶、大气污染等人为因素对中国气候变化影响的研究进展。结果指出：北极涛动、东亚季风这两个大气环流因素对中国气候异常变化有至关重要的作用，同时El Nino和La Nina事件和太平洋年代际振荡的海表温度异常变化也对中国气候产生了一定的影响。但是有关大气气溶胶和大气污染物对中国气候的影响作用还有待于进一步研究，自然原因仍然是影响中国气候变化的主要原因。

DOI

[Bai Aijuan, Zhai Panmao.On natural causes of climate change in China. Scientia Meteorologica Sinica, 2007, 27(5): 584-590.]

[30]
邓伟涛, 孙照渤, 曾刚, 等. 中国东部夏季降水型的年代际变化及其与北太平洋海温的关系. 大气科学, 2009, 33(4): 835-846.采用中国160站降水资料、NOAA ERSST海温资料以及ERA－40大气再分析资料, 分析了中国东部夏季降水型的年代际变化特征及其与北太平洋海温的可能联系。结果表明: 中国东部夏季降水型在近50年中经历了两次年代际变化, 第1次发生在20世纪70年代中后期, 北太平洋中纬度地区冬季海温由正距平向负距平转变, 太平洋年代际振荡(PDO, Pacific decadal oscillation) 由负位相向正位相转变, 通过影响东亚夏季风环流, 使东亚夏季风减弱, 中国东部夏季降水从北到南呈现出“＋－＋” 转变为“－＋－”的三极分布形态, 这次年代际变化体现了同一模态正负位相的转变; 第2次发生在20世纪80年代末90年代初, 北太平洋海温转变为日本以南西北太平洋的正距平分布, 同时菲律宾群岛附近海温偏暖, 西太平洋副热带高压偏南偏西, 使得中国东部夏季降水由北至南转变成“－＋”的偶极分布形态, 这次年代际变化体现了一种模态向另一种模态的转变。

DOI

[Deng Weitao, Sun Zhaobo, Zeng Gang, et al.Inter-decadal variation of summer precipitation pattern over eastern China and its relationship with the north Pacific SST. Chinese Journal of Atmospheric Sciences, 2009, 33(4): 835-846.]

[31]
Ding Yihui, Sun Ying, Wang Zunya, et al.Inter-decadal variation of the summer precipitation in China and its association with decreasing Asian summer monsoon. Part II: Possible causes. International Journal of Climatology, 2009, 29(13): 1926-1944.The present article is the second part of a study on the inter-decadal variability of the summer precipitation in East China, which mainly addresses the possible cause of this change. Firstly, an updated analysis of the long-term variations of snow cover, snow days and snow depth in the preceding winter and spring over the Tibetan Plateau (TP) was done by using station and satellite data. The a...

DOI

[32]
吕俊梅, 祝从文, 琚建华, 等. 近百年中国东部夏季降水年代际变化特征及其原因. 大气科学, 2014, 38(4): 782-794.本文利用测站降水观测资料分析过去一百多年中国东部华北、长江流域以及华南夏季降水的年代际变化特征发现，尽管这三个地区的夏季降水具有不同的年代际转折时期，但是均同时在1910年代初期、1920年代初期、1940年代中期、1960年代中期、1970年代末期以及1990年代初期发生了跃变。近一百年间不同年代际时期东部夏季降水的分布型主要以南正北负或者南负北正的偶极型为主，并且无论是偶极型分布还是三极型分布，两个相邻年代际时期中国东部降水分布型发生完全反向变化的概率较高（60%）。此外，夏季的PDO、冬季的AO以及春季的北极海冰也同时在1920年代末期、1940年代中期、1970年代末期以及1990年代中期左右发生了跃变，这几次跃变时期与中国东部三个不同地区夏季降水发生跃变的时期一致，表现出近百年来太平洋年代振荡（PDO）、北极涛动（AO）以及北极海冰这三个因子对中国东部夏季降水年代际变化的协同作用。<br>在年代际时间尺度上，夏季的PDO与华北夏季降水显著负相关。PDO的年代际变化能够在500 hPa位势高度场中激发出太平洋—日本（PJ）型年代际遥相关波列；同时在850 hPa风场中激发出类似于影响华北夏季降水年代际变化的大气环流型，从而影响华北降水的年代际变化。冬半年的AO与长江流域夏季降水存在显著正相关关系。冬季到春季正位相的AO导致亚洲大陆南部处于湿冷状态，土壤湿度的记忆性可将这种状态延续到夏季。因此，夏季海陆热力对比减弱，东亚夏季风发生年代际减弱，相应地长江流域的降水年代际增多。春季北极海冰与华南夏季降水显著负相关，北极海冰的年代际异常能在500 hPa位势高度场中激发出与静止Rossby波异常传播相联系的欧亚—华南年代际遥相关波列，从而影响华南降水的年代际变化。

DOI

[Lv Junmei, Zhu Congwen, Ju Jianhua, et al.Interdecadal variability in summer precipitation over east China during the past 100 years and its possible causes. Chinese Journal of Atmospheric Sciences, 2014, 38(4): 782-794.]

[33]
Lei Yonghui, Hoskins B, Slingo J.Exploring the interplay between natural decadal variability and anthropogenic climate change in summer rainfall over China. Part I: Observational evidence. Journal of Climate, 2011, 24(17): 4584-4599.

[34]
徐康, 祝从文, 何金海. 近50年环贝加尔湖区变暖对中国华北夏季降水的影响机理. 高原气象, 2011, 30(2): 309-317.<FONT face=Verdana>利用1951-2007年中国722站逐月降水观测资料、 NCEP/NCAR再分析资料及1958-2002年逐月欧洲中心的ERA-40再分析资料， 分析了近57年中国华北夏季降水的年代际变化特征， 重点讨论了全球变暖背景下环贝加尔湖地表气温升高对中国华北夏季降水长期变化的影响机理。结果表明， 华北夏季降水长期减少趋势与全球变暖存在密切联系， 环贝加尔湖地区的地表气温升高是影响中国华北夏季降水长期变化的关键因子之一。根据热成风原理， 该地区地表气温的持续升高导致蒙古国和中国华北区对流层温度经向梯度和纬向风垂直切变的减小， 从而对流层的大气斜压性减弱, 易维持暖性异常反气旋环流， 导致环贝加尔湖地区气旋活动的频率和华北地区夏季降水持续减少。<BR></FONT>

[Xu Kang, Zhu Congwen, He Jinhai.Impact of the surface air temperature warming around Lake Baikal on trend of summer precipitation in north China in the past 50 years. Plateau Meteorology, 2011, 30(2): 309-317.]

[35]
Wang Bin, Liu Jian, Kim H J, et al.Northern Hemisphere summer monsoon intensified by mega-El Niño/southern oscillation and Atlantic multi-decadal oscillation. Proceedings of the National Academy of Sciences, 2013, 110(14): 5347-5352.

[36]
Liu Jian, Wang Bin, Cane M A, et al.Divergent global precipitation changes induced by natural versus anthropogenic forcing. Nature, 2013, 493(7434): 656-659.As a result of global warming, precipitation is likely to increase in high latitudes and the tropics and to decrease in already dry subtropical regions(1). The absolute magnitude and regional details of such changes, however, remain intensely debated(2,3). As is well known from El Nino studies, sea-surface-temperature gradients across the tropical Pacific Ocean can strongly influence global rainfall(4,5). Palaeoproxy evidence indicates that the difference between the warm west Pacific and the colder east Pacific increased in past periods when the Earth warmed as a result of increased solar radiation(6-9). In contrast, in most model projections of future greenhouse warming this gradient weakens(2,10,11). It has not been clear how to reconcile these two findings. Here we show in climate model simulations that the tropical Pacific sea-surface-temperature gradient increases when the warming is due to increased solar radiation and decreases when it is due to increased greenhouse-gas forcing. For the same global surface temperature increase the latter pattern produces less rainfall, notably over tropical land, which explains why in the model the late twentieth century is warmer than in the Medieval Warm Period (around AD 1000-1250) but precipitation is less. This difference is consistent with the global tropospheric energy budget(12), which requires a balance between the latent heat released in precipitation and radiative cooling. The tropospheric cooling is less for increased greenhouse gases, which add radiative absorbers to the troposphere, than for increased solar heating, which is concentrated at the Earth's surface. Thus warming due to increased greenhouse gases produces a climate signature different from that of warming due to solar radiation changes.

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[37]
张冬峰, 高学杰, 罗勇, 等. RegCM4.0对一个全球模式20世纪气候变化试验的中国区域降尺度: 温室气体和自然变率的贡献. 科学通报, 2015, 60(17): 1631-1642.近几十年来,中国区域气候经历了以变暖和东部降水呈现＂南涝北旱＂分布特征为主的变化.这里基于一个区域气候模式（Reg CM4.0）历史模拟和归因试验的对比,探讨了温室气体排放和自然变率分别对上述特征形成及各大水文流域气候变化成因的可能贡献.试验中Reg CM4.0的分辨率取为50 km,积分时间为1961~2005年,两个试验的驱动场分别来自于BCC_CSM1.1全球气候模式的历史试验和归因试验结果.分析结果表明,1961~2005年观测中出现的气候变暖现象,在所有流域均主要是由于人为温室气体排放引起的,在大部分流域自然变率亦有所贡献,中国区域平均的变暖中,人为温室气体排放所产生的作用达到80%.中国东部降水的＂南涝北旱＂分布变化,则可能主要是自然变率起了主导作用,人为温室气体排放在一定程度上减弱了这种变化的强度;中国西北地区的降水增加,可能主要源于人为温室气体排放的贡献,自然变率的作用与其相反,是导致降水减少的.同时指出,分析结果中关于气温的结论相对可靠性较高,降水的结论尚存在较大不确定性,未来需开展进一步的深入研究.

DOI

[Zhang Dongfeng, Gao Xuejie, Luo Yong, et al.Downscaling a 20th century climate change of a global model for China from RegCM4.0: Attributable contributions of greenhouse gas emissions and natural climate variability. Chinese Science Bulletin, 2015, 60(17): 1631-1642.]

[38]
Hurrell J W, Holland M M, Gent P R, et al.The Community Earth System Model: A framework for collaborative research. Bulletin of the American Meteorological Society, 2013, 94(9): 1339-1360.The Community Earth System Model (CESM) is a flexible and extensible community tool used to investigate a diverse set of Earth system interactions across multiple time and space scales. This global coupled model significantly extends its predecessor, the Community Climate System Model, by incorporating new Earth system simulation capabilities. These comprise the ability to simulate biogeochemical cycles, including those of carbon and nitrogen, a variety of atmospheric chemistry options, the Greenland Ice Sheet, and an atmosphere that extends to the lower thermosphere. These and other new model capabilities are enabling investigations into a wide range of pressing scientific questions, providing new foresight into possible future climates and increasing our collective knowledge about the behavior and interactions of the Earth system. Simulations with numerous configurations of the CESM have been provided to phase 5 of the Coupled Model Intercomparison Project (CMIP5) and are being analyzed by the broad community of scientists. Additionally, the model source code and associated documentation are freely available to the scientific community to use for Earth system studies, making it a true community tool. This article describes this Earth system model and its various possible configurations, and highlights a number of its scientific capabilities.

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[39]
陈晓晨, 徐影, 许崇海, 等. CMIP5全球气候模式对中国地区降水模拟能力的评估. 气候变化研究进展, 2014, 10(3): 217-225.使用多种观测资料和43个参加耦合模式比较计划第五阶段（CMIP5）的全球气候模式模拟数据，评估分析了全球气候模式对中国地区1980&mdash;2005年降水特征的模拟能力。结果表明：多数CMIP5模式能够模拟出中国降水由西北向东南递增的分布特点，这与耦合模式比较计划第三阶段（CMIP3）的模式模拟结果类似，但华南地区降水模拟偏少，西部高原地区降水模拟偏多。模式能够较好地模拟出降水冬弱夏强的季节变化特征，但降水模拟系统性偏多。从EOF分析结果来看，多数CMIP5模式可以再现中国地区年平均降水的时空变化特征，集合平均的表现优于CMIP3。多模式集合在月、季、年时间尺度下模拟的平均值优于大部分单个模式的结果。CMIP5中6个中国模式的模拟能力与其他模式相当，其中FGOALS-g2、BCC-CSM1-1-m的模拟能力相对较好。

DOI

[Chen Xiaochen, Xu Ying, Xu Chonghai, et al.Assessment of precipitation simulations in China by CMIP5 multi-models. Advances in Climate Change Research, 2014, 10(3): 217-225.]

[40]
Lei Yonghui, Hoskins B, Slingo J.Natural variability of summer rainfall over China in HadCM3. Climate Dynamics, 2014, 42(1-2): 417-432.ABSTRACT Summer rainfall over China has shown decadal variability in the past half century, which has resulted in major north-south shifts in rainfall with important implications for flooding and water resource management. This study has demonstrated how multi-century climate model simulations can be used to explore interdecadal natural variability in the climate system in order to address important questions around recent changes in Chinese summer rainfall, and whether or not anthropogenic climate change is playing a role. Using a 1,000-year simulation of HadCM3 with constant pre-industrial external forcing, the dominant modes of total and interdecadal natural variability in Chinese summer rainfall have been analysed. It has been shown that these modes are comparable in magnitude and in temporal and spatial characteristics to those observed in the latter part of the twentieth century. However, despite 1,000 years of model simulation it has not been possible to demonstrate that these modes are related to similar variations in the global circulation and surface temperature forcing occurring during the latter half of the twentieth century. This may be in part due to model biases. Consequently, recent changes in the spatial distribution of Chinese summer rainfall cannot be attributed solely to natural variability, nor has it been possible to eliminate the likelihood that anthropogenic climate change has been the driving factor. It is more likely that both play a role.

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[41]
Hannachi A, Jolliffe I T, Stephenson D B.Empirical orthogonal functions and related techniques in atmospheric science: A review. International Journal of Climatology, 2007, 27(9): 1119-1152.Abstract Climate and weather constitute a typical example where high dimensional and complex phenomena meet. The atmospheric system is the result of highly complex interactions between many degrees of freedom or modes. In order to gain insight in understanding the dynamical/physical behaviour involved it is useful to attempt to understand their interactions in terms of a much smaller number of prominent modes of variability. This has led to the development by atmospheric researchers of methods that give a space display and a time display of large space-time atmospheric data. Empirical orthogonal functions (EOFs) were first used in meteorology in the late 1940s. The method, which decomposes a space-time field into spatial patterns and associated time indices, contributed much in advancing our knowledge of the atmosphere. However, since the atmosphere contains all sorts of features, e.g. stationary and propagating, EOFs are unable to provide a full picture. For example, EOFs tend, in general, to be difficult to interpret because of their geometric properties, such as their global feature, and their orthogonality in space and time. To obtain more localised features, modifications, e.g. rotated EOFs (REOFs), have been introduced. At the same time, because these methods cannot deal with propagating features, since they only use spatial correlation of the field, it was necessary to use both spatial and time information in order to identify such features. Extended and complex EOFs were introduced to serve that purpose. Because of the importance of EOFs and closely related methods in atmospheric science, and because the existing reviews of the subject are slightly out of date, there seems to be a need to update our knowledge by including new developments that could not be presented in previous reviews. This review proposes to achieve precisely this goal. The basic theory of the main types of EOFs is reviewed, and a wide range of applications using various data sets are also provided. Copyright © 2007 Royal Meteorological Society

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[42]
North G R.Empirical orthogonal functions and normal modes. Journal of the Atmospheric Sciences, 1984, 41: 879-887.Abstract An attempt to provide physical insight into the empirical orthogonal function (EOF) representation of data fields by the study of fields generated by linear stochastic models is presented in this paper. In a large class of these models, the EOFs at individual Fourier frequencies coincide with the orthogonal mechanical modes of the system-provided they exist. The precise mathematical criteria for this coincidence are derived and a physical interpretation is provided. A scheme possibly useful in forecasting is formally constructed for representing any stochastic field by a linear Hermitian model forced by noise.

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[43]
North G R, Bell T L, Cahalan R F, et al.Sampling errors in the estimation of empirical orthogonal functions. Monthly Weather Review, 1982, 110: 699-706.Abstract Empirical Orthogonal Functions (EOF's), eigenvectors of the spatial cross-covariance matrix of a meteorological field, are reviewed with special attention given to the necessary weighting factors for gridded data and the sampling errors incurred when too small a sample is available. The geographical shape of an EOF shows large intersample variability when its associated eigenvalue is “close” to a neighboring one. A rule of thumb indicating when an EOF is likely to be subject to large sampling fluctuations is presented. An explicit example, based on the statistics of the 500 mb geopotential height field, displays large intersample variability in the EOF's for sample sizes of a few hundred independent realizations, a size seldom exceeded by meteorological data sets.

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[44]
Torrence C, Compo G P.A practical guide to wavelet analysis. Bulletin of the American Meteorological Society, 1998, 79(1): 61-78.

[45]
PAGES. Science Plan and Implementation Strategy: IGBP Report No. 57. Stockholm: IGBP Secretariat, 2009.The IGAC Science Plan and Implementation Strategy lays out the scientific objectives and key research issues of the atmospheric chemistry project of the International Geosphere Biosphere Programme (IGBP) as both IGAC and IGBP enter their second phase. It also lays out a framework for addressing these objectives and issues, recognizing the need for collaboration with partner programmes and projects. The scientific focus of this document emerged from the first decade of IGAC research, much of which was conducted in the context of focused, intensive measurement campaigns. The scope of IGAC in its next phase includes both regional characterisation and the extension into issues that cross more expansive boundaries in space, time and discipline. While local and regional-scale atmospheric chemical composition will be a primary focus, it is now clear that issues such as intercontinental transport and transformation of chemically active species and the interactions between atmospheric chemistry and climate must also be addressed in order to better understand atmospheric chemical composition and to provide guidance to the public and policy-making community.

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