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1.
欧亚大陆春季融雪量与东亚夏季风的可能联系 总被引：4，自引：3，他引：1
通过对观测资料的分析, 本文研究了春季欧亚大陆融雪量与东亚夏季风的关系, 并初步讨论了其可能联系机制。研究表明, 春季融雪量EOF (Empirical Orthogonal Function) 第一模态表现出年代际变化特征, 这与东亚夏季风和中国夏季降水的年代际转型具有非常好的一致性。而EOF第二模态与东亚夏季风在年际尺度上具有同位相变化关系, 当春季融雪量在东西伯利亚和巴尔喀什湖附近异常偏多时, 后期在东亚地区容易出现由高纬至低纬的“负—正—负”经向波列结构。融雪量异常偏少时, 情况则相反。文中初步分析了春季融雪量异常与后期夏季东亚地区大气环流出现经向波列结构的可能联系机制, 指出东西伯利亚以及巴尔喀什湖附近异常偏多的春季融雪量能够在该地区促使位势高度场表现为正异常, 随着时间的演变, 巴尔喀什湖附近地区的高压向东移动发展, 东西伯利亚地区的高压一部分向低纬移动, 可能造成夏季东亚地区的经向波列结构, 进而对东亚的天气和气候产生影响。 相似文献
2.
欧亚中高纬春季地表感热异常与长江中下游夏季降水的可能联系 总被引：1，自引：1，他引：0
利用国家气候中心提供的中国区域753站降水观测资料、ECMWF逐月地表感热通量再分析资料和NECP/NCAR再分析资料,讨论了欧亚大陆中高纬春季地表感热异常与长江中下游夏季降水之间的联系及其相关的物理机制。分析发现欧亚大陆中高纬春季地表感热异常与长江中下游地区夏季降水存在显著的正相关:感热偏强期,长江中下游夏季降水偏多;感热偏弱期,长江中下游夏季降水偏少。春季感热异常偏强时,夏季东亚副热带西风急流主体位置偏东、强度偏强、范围偏大,长江中下游地区主要受辐合上升气流控制,水汽输送条件好,降水异常偏多。而春季感热偏弱时,情况大致相反,则夏季降水异常偏少。研究表明欧亚大陆中高纬春季地表感热通量异常变化对我国长江中下游夏季降水预测具有一定的指示意义。 相似文献
3.
有关南半球大气环流与东亚气候的关系研究的若干新进展 总被引：14，自引：15，他引：14
南半球大气环流是全球大气环流的重要组成部分,也是影响气候变化和亚洲季风系统的一个重要因素.中国气象学家很早就注意到南半球大气环流对东亚夏季风降水的影响.近年来,有关南半球气候变率的研究目前正受到世界气象学家越来越多的关注.南半球中高纬大气资料的丰富及南极涛动的确定,使得认识南半球高中纬环流的年际变动规律及其与东亚气候关系成为可能.本文主要介绍近年来有关南极涛动的年际变化与沙尘天气发生频次及东亚冬春季气候的关系,古气候资料揭示的南极涛动与华北降水的关系,以及南半球大气环流与长江中下游夏季降水的关系和南极涛动变率的可预测性等方面的研究进展.并对未来研究方向作了初步的展望. 相似文献
4.
利用统计方法对春季(4~5月)南半球环状模(SAM)与夏季(6~8月)中国降水的关系作了分析,发现春季南半球环状模指数(SAMI)与夏季长江中下游降水之间存在显著的正相关关系。春季SAM偏强的同期对流层下层在欧亚大陆存在一以蒙古高原和天山山脉为中心的异常反气旋对,从中国东北到华南中纬度地区均为异常的偏北气流控制。这种环流异常形式可以持续到夏季并加强,致使东亚夏季风减弱;春季SAM偏强,夏季西太平洋副热带高压西部脊强度加强,位置偏西,这些异常环流都有利于长江中下游地区降水偏多。另外,春季SAM偏强,夏季长江中下游地区水汽含量增大,向上的垂直运动得到加强,为该地区降水偏多提供了基本的水汽条件。春季SAM偏弱时,夏季东亚大气环流和水汽条件相反。因此,春季SAM为夏季长江中下游汛期降水提供了一有用的前期信号。 相似文献
5.
南半球环流变化对东亚夏季风的影响 总被引：14，自引：2，他引：12
南半球环流是影响东亚夏季风季节内、季节到年际变化的重要因子之一.作者系统综述了南半球环流各系统包括连接两半球的越赤道气流、马斯克林高压和澳大利亚高压、南极涛动和南极海冰等对东亚夏季风环流和中国夏季降水的影响.特别是,近年来的研究揭示了南极涛动是影响东亚夏季风年际变化的强信号.当南极涛动偏强时,马斯克林高压和澳大利亚高压和相关的越赤道气流也趋于偏强.同时,西太平洋副热带高压偏西偏南,强度增强,长江流域降水偏多,其两侧降水偏少.这对中国夏季降水的预测有重要的应用价值.最后提出了一些相关的科学问题以供进一步研究.
相似文献
6.
El Ni?o对东亚夏季风和夏季降水季节内变化的影响 总被引：3，自引：0，他引：3
基于1979~2012年候平均再分析资料,合成分析了El Ni?o对东亚夏季风和夏季降水季节内变化的影响。结果表明,在El Ni?o衰减年夏季,西太平洋副热带高压(副高)明显偏强,位置偏向西南。副高的这种异常特征随夏季的季节进程有明显变化,初夏异常较弱,盛夏期间异常达到最强。此外,根据东亚夏季风降水呈现阶段式北进的特征,将夏季分为华南前汛期、江淮梅雨期、华北和东北雨期以及华南后汛期来分析东亚夏季风和降水的季节内变化。在上述各个时期,大气对流层低层表现为一致的环流异常型,副高及其以南区域为异常反气旋,其北部为异常气旋。这种异常环流型加强了副高南部偏东风及其北部偏北风,增强了热带水汽输送和高纬度地区冷空气的入侵,二者结合造成主汛期地区降水增加。需要强调的是,上述环流异常型随东亚夏季风逐步向北推移,导致东亚各地区的主汛期降水增加,非主汛期降水减少,降水分布更为集中。 相似文献
7.
South China spring rainfall (SCSR) is a unique feature during the seasonal transition from the winter half-year to summer half-year. Abnormal SCSR has great impacts on crop harvests. Seeking previous predictability sources, particularly persistent precursors, is of practical importance in the seasonal prediction of SCSR. The present study investigates the relationship between SCSR and preceding-summer warm pool ocean heat content (WPHC). The SCSR-WPHC relationship is not stationary and has a remarkable interdecadal change around 1983. Before 1983, SCSR and preceding-summer WPHC have a close relationship, with a temporal correlation coefficient (TCC) of ?0.54. After 1983, the relationship disappears, with a TCC of ?0.18. It is further found that the WPHC-associated sea surface temperature anomaly (SSTA) pattern in the simultaneous spring during the two periods presents dissimilar evolutionary features. Before 1983, a La Ni?a-like SSTA presents a fast transition during the winter and alters to a developing El Ni?o during the following spring. The warm SSTA is confined to a limited region over the eastern Pacific. Therefore, the rainfall and circulation responses over the equatorial Maritime Continent are relatively weak. In turn, the Rossby wave response in terms of the cyclonic anomaly to the Maritime Continent diabatic heating is weak and confined to the South China Sea and Philippine Sea, which leads to high pressure and suppressed rainfall over south China, establishing an intimate SCSR–WPHC relationship. However, after 1983, because the La Ni?a-like SSTA pattern can persist for more than a year, the rainfall diabatic heating over the Maritime Continent during springtime is enhanced, resulting in a much larger cyclonic response over East Asia but insignificant rainfall anomalies over south China. Therefore, the SCSR–WPHC relationship becomes weak. Wavelet analysis suggests that the change in the dominant period of WPHC variation is probably responsible for the different SSTA evolutions and corresponding atmospheric responses. 相似文献
8.
Comparison of Products from ERA-40, NCEP-2, and CRU with Station Data for Summer Precipitation over China 总被引：4，自引：0，他引：4
Summer precipitation products from the 45-Year European Centre for Medium-Range Weather Forecast (ECMWF) Reanalysis (ERA-40), and NCEP-Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (NCEP-2), and Climatic Research Unit (CRU) TS 2.1 dataset are compared with the corresponding observations over China in order to understand the quality and utility of the reanalysis datasets for the period 1979–2001. The results reveal that although the magnitude and location of the rainfall belts differ among the reanalysis, CRU, and station data over South and West China, the spatial distributions show good agreement over most areas of China. In comparison with the observations in most areas of China, CRU best matches the observed summer precipitation, while ERA-40 reports less precipitation and NCEP-2 reports more precipitation than the observations. With regard to the amplitude of the interannual variations, CRU is better than either of the reanalyses in representing the corresponding observations. The amplitude in NCEP-2 is stronger but that of ERA-40 is weaker than the observations in most study domains. NCEP-2 has a more obvious interannual variability than ERA-40 or CRU in most areas of East China. Through an Empirical orthogonal function (EOF) analysis, the main features of the rainfall belts produced by CRU agree better with the observations than with those produced by the reanalyses in the Yangtze-Huaihe River valley. In East of China, particularly in the Yangtze-Huaihe River valley, CRU can reveal the quasi-biennial oscillation of summer precipitation represented by the observations, but the signal of ERA-40 is comparatively weak and not very obvious, whereas that of NCEP-2 is also weak before 1990 but very strong after 1990. The results also suggest that the magnitude of the precipitation difference between ERA-40 and the observations is smaller than that between NCEP-2 and the observations, but the variations represented by NCEP-2 are more reasonable than those given by ERA-40 in most areas of East China to some extent. 相似文献
9.
秋季南极涛动异常对冬季中国南方降水的影响 总被引：2，自引：0，他引：2
本文针对秋季南极涛动（AAO）和冬季中国南方降水的关系作了研究,发现两者之间存在显著的反向年际变化关系。AAO正（负）异常年,副热带西风急流显著增强（减弱）,欧洲西部槽、乌拉尔山高压脊和东亚沿岸大槽均偏强（偏弱）,阿留申低压、南支槽和西太平洋副高偏弱（偏强）,西南急流上的扰动不活跃（活跃）,我国大部分地区出现异常偏北风（偏南风）和OLR弱正距平,导致南方降水偏少（偏多）。两半球存在东亚—南半球高纬地区和纵贯太平洋南北的两个遥相关型,海洋性大陆对流活动可能是秋季AAO影响南方冬季降水的一个机制。因此,秋季南极涛动的异常很可能对预测我国南方冬季降水有显著指示意义。 相似文献
10.
东亚夏季风年际变率及其与中、高纬度大气环流以及外强迫异常的联系 总被引：8，自引：2，他引：6
利用欧洲中心35年(1968-2002年)月平均再分析资料(ERA-40),通过矢量经验正交分析方法,研究了东亚夏季风年际变率的第2、3优势模态及其与中、高纬度大气环流和外强迫异常之间的联系.这两个优势模态均与北半球中、高纬度大气环流异常有密切的关系,累计解释协方差超过了东亚夏季风的第1模态.东亚夏季风变率的第2模态解... 相似文献
11.
East Asian summer monsoon circulation structure controlled by feedback of condensational heating 总被引：1，自引：0，他引：1
The East Asian summer monsoon (EASM) features strong humid low-level southerly flows and abundant rainfall over the subtropical East Asia. This study identified how condensational heating generated by the EASM rainfall can affect the EASM circulation by contrasting two 10-member ensembles of atmospheric General Circulation Model experiments with Community Climate Model version 3/National Center for Atmospheric Research respectively with and without feedback of condensational heating over the East Asian domain. Major results inferred from the experiments are as follows. Condensational heating is found to absolutely dominate diabatic heating over East Asia. Exclusion of the feedback of condensational heating leads to a significant weakening of summertime tropospheric warming over land and thus a large reduction of the land-sea thermal contrast between entire Asian continent and surrounding oceans. Associated with this, the lower-level EASM flows are weakened, South Asian High at 200 hPa migrates southward with reduced intensity and breaks over East Asia with southerly flows prevailing in the upper troposphere, in contrast to northerly flows in reality. Consequently, local EASM meridional cell disappears and the baroclinic structure featured by the EASM circulation that is dynamically determined by convective condensational heating over East Asia is altered to a barotropic structure. Therefore, it is concluded that the feedback of condensational heating acts to largely enhance lower-level flows of the EASM and essentially determine its baroclinic structure and meridional cell, once the solar radiation and inhomogeneity of the Earth’s surface form low-level monsoon flows in East Asia by enhancing land-sea thermal contrast. 相似文献
12.
Based on an improved objective cyclone detection and tracking algorithm, decadal variations in extratropical cyclones in northern East Asia are studied by using the ECMWF 40 Year Reanalysis (ERA-40) sea-level pressure data during 1958-2001. The results reveal that extratropical cyclone activity has displayed clear seasonal, interannual, and decadal variability in northern East Asia. Spring is the season when cyclones occur most frequently. The spatial distribution of extratropical cyclones shows that cyclon... 相似文献
13.
利用我国地面观测站降水资料以及欧洲中期数值预报中心 (ECMWF) 的月平均再分析资料, 研究了在全球平均表面气温偏冷和偏暖阶段, 我国东部降水开始和结束时间以及雨带南北移动的变化, 并分析了与东部降水变化相关联的大气环流特征。结果表明:近40年, 20世纪60—70年代全球平均表面气温处于一个相对偏冷时期, 而80—90年代处于偏暖时期; 在这样的变暖背景下, 我国东部地区年总降水量呈现出“南涝北旱”异常特征, 与冷位相比较, 在暖位相阶段长江流域年总降水量明显增加, 而华北地区降水量减少, 其中长江流域降水的增加主要是由夏季降水增加引起的, 3月长江中下游降水增加也很重要, 北方的降水减少主要是由从盛夏到初秋的降水减少引起的。平均而言, 暖位相阶段我国南方强降水开始时间较早、结束较晚, 持续时间较长, 而北方强降水开始较晚, 持续时间较短。从春末到夏季, 冷位相时我国东部强降水带表现出从华南、经过长江流域向华北移动的特征, 而在暖位相时强降水主要集中在长江流域, 从华南向华北移动的特征不明显。雨带的这种异常变化与东亚大气环流有关, 在暖位相时夏季东亚大陆低压比冷位相时弱, 而鄂霍次克海高压偏强, 西太平洋副热带高压位置偏南, 使夏季东亚副热带地区的西南风减弱, 梅雨锋加强, 导致雨带滞留在长江流域, 使长江流域降水增加、北方降水减少。 相似文献
14.
大气热源年代际异常与20世纪70年代末期东亚夏季风年代际减弱 总被引：2，自引：1，他引：1
利用1958-2001年ERA-40再分析资料计算大气热源,统计分析了亚洲季风区及其邻近海域大气热源年代际变异的典型模态;利用线性斜压干模式,模拟了夏季大气对大气热源年代际异常的响应,揭示了大气热源年代际异常与1970s末期东亚夏季风年代际减弱的关系。结果表明:近50 a来亚洲及其邻近海域夏季整层大气热源变异主要表现为年代际变化特征,其年代际位相转换发生在1970s中后期,这与东亚夏季风年代际减弱的时间一致;菲律宾附近海域和中国西南地区是与东亚夏季风年代际减弱有直接联系的两个热源异常关键区;东亚夏季风年代际减弱最直接地表现为这两个关键区热源异常的共同作用,而赤道中东太平洋、赤道印度洋大气热源增强则通过大气遥响应机制影响菲律宾附近海域低层大气环流异常对东亚夏季风变异起相反的贡献。 相似文献
15.
The interannual variation of East Asia summer monsoon (EASM) rainfall exhibits considerable differences between early summer [May–June (MJ)] and peak summer [July–August (JA)]. The present study focuses on peak summer. During JA, the mean ridge line of the western Pacific subtropical High (WPSH) divides EASM domain into two sub-domains: the tropical EA (5°N–26.5°N) and subtropical-extratropical EA (26.5°N–50°N). Since the major variability patterns in the two sub-domains and their origins are substantially different, the Part I of this study concentrates on the tropical EA or Southeast Asia (SEA). We apply the predictable mode analysis approach to explore the predictability and prediction of the SEA peak summer rainfall. Four principal modes of interannual rainfall variability during 1979–2013 are identified by EOF analysis: (1) the WPSH-dipole sea surface temperature (SST) feedback mode in the Northern Indo-western Pacific warm pool associated with the decay of eastern Pacific El Niño/Southern Oscillation (ENSO), (2) the central Pacific-ENSO mode, (3) the Maritime continent SST-Australian High coupled mode, which is sustained by a positive feedback between anomalous Australian high and sea surface temperature anomalies (SSTA) over Indian Ocean, and (4) the ENSO developing mode. Based on understanding of the sources of the predictability for each mode, a set of physics-based empirical (P-E) models is established for prediction of the first four leading principal components (PCs). All predictors are selected from either persistent atmospheric lower boundary anomalies from March to June or the tendency from spring to early summer. We show that these four modes can be predicted reasonably well by the P-E models, thus they are identified as the predictable modes. Using the predicted PCs and the corresponding observed spatial patterns, we have made a 35-year cross-validated hindcast, setting up a bench mark for dynamic models’ predictions. The P-E hindcast prediction skill represented by domain-averaged temporal correlation coefficient is 0.44, which is twice higher than the skill of the current dynamical hindcast, suggesting that the dynamical models have large rooms to improve. The maximum potential attainable prediction skills for the peak summer SEA rainfall is also estimated and discussed by using the PMA. High predictability regions are found over several climatological rainfall centers like Indo-China peninsula, southern coast of China, southeastern SCS, and Philippine Sea. 相似文献
16.
This study investigates the relationship between the soil temperature in May and the East Asian summer monsoon （EASM） precipitation in June and July using station observed soil temperature data over Northwest China from 1971 to 2000.It is found that the memory of the soil temperature at 80-cm depth can persist for at least 2 months,and the soil temperature in May is closely linked to the EASM precipitation in June and July.When the soil temperature is warmer in May over Northwest China,less rainfall occurs over the Yangtze and Huaihe River valley but more rainfall occurs over South China in June and July.It is proposed that positive anomalous soil temperature in May over Northwest China corresponds to higher geopotential heights over the most parts of the mainland of East Asia,which tend to weaken the ensuing EASM.Moreover,in June and July,a cyclonic circulation anomaly occurs over Southeast China and Northwest Pacific and an anticyclonic anomaly appears in the Yangtze and Huaihe River valley at 850 hPa.All the above tend to suppress the precipitation in the Yangtze and Huaihe River valley.The results also indicate that the soil temperature in May over Northwest China is closely related to the East Asia/Pacific （EAP） teleconnection pattern,and it may be employed as a useful predictor for the East Asian summer monsoon rainfall. 相似文献
17.
Temporal Variations of the Spring Persistent Rains and South China Sea Sub-high and Their Correlations to the Circulation and Precipitation of the East Asian Summer Monsoon 
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下载免费PDF全文 National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish the onset-pentad time index of the spring persistent rains （SPR） and the decay-pentad time index of the South China Sea （SCS） sub-high. These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asian summer monsoon （EASM）. Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibetan Plateau （TP） strengthens, which makes abnormal anti-cyclonic circulation （cyclonic convergent circulation weakens） appear over southeastern China. When the decay of SCS sub-high delays, abnormal flood prevails over the middle and lower reaches of the Yangtze River （MLYR） and to the south. That is mainly caused by EASM weakening while SCS sub-high strengthening, then the abnormal southwesterly over South China and the abnormal northerlies of anti-cyclonic circulation around the TP converge over the Yangtze Valley. The two indexes have high correlations with multivariate ENSO index （MEI） in March, indicating that the climate abnormity in East Asia is related to global climate abnormity tightly. The two time indexes are independent of each other, which is favorable for the prediction of the anomalies of the circulation and precipitation of EASM. From this point of view, we must take the global climate background into account when we analyze and predict the East Asian summer circulation and precipitation. 相似文献
18.
The correlation analysis has been used to study the relationship between spring soil moisture over China and East Asian summer monsoon (EASM). It is shown that EASM has a strong positive correlation with spring soil moisture over southwest China and the Great Bend region of the Yellow River. A standard soil moisture index (SMI) has been defined using the observed soil moisture of the two regions. The results show that SMI has a strong correlation with EASM. The years of strong (weak) SMI are associated with stronger (weaker) summer monsoon circulation. In the years of strong SMI, the west Pacific subtropical high is much northward in position and weaker in intensity; the westerlies zone is also more to the north. All of these make EASM circulation move northward and cause the rainfall belt to relocate to North China and Northeast China. SMI can reflect the variation of the summer rainfall anomaly over eastern China. In the years of strong SMI, the rainfall belt is mainly located over the northem part of China.However, during the weak years, the summer rainfall belt is largely located over the mid- and lower- reaches of the Yangtze River. Additionally, the SMI has obvious oscillations of quasi 4-6 years and quasi 2 years. Moreover, negative SMI predicts EASM better than positive SMI. 相似文献
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利用1960~2010年ERA-20C再分析资料和中国东部站点降水观测资料,探讨了我国东部春季极端降水与欧亚大陆地表感热通量的联系和可能影响途径。结果发现,当春季欧亚大陆中纬度巴尔喀什湖以西及贝加尔湖以南区域地表感热通量偏弱（强）,我国东部沿海地区地表感热通量偏强（弱）时,我国东部春季极端降水呈现南少（多）北多（少）的反相分布特征。当春季欧亚大陆中纬度关键区地表感热偏弱,低纬度关键区地表感热通量偏强时,春季副热带西风急流偏弱、位置偏北,我国东部北方地区大气斜压不稳定和对流不稳定偏强,北方地区极端降水偏强,而南方地区大气斜压不稳定和对流不稳定偏弱,南方地区极端降水偏弱。当春季欧亚大陆中纬度关键区地表感热偏强,低纬度关键区地表感热通量偏弱,我国东部极端降水的情况大致相反。 相似文献
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东亚夏季风异常活动的多模态特征:不同再分析资料的比较分析 总被引：2，自引：1，他引：1
利用1979～2002年ERA-40、ERA interim、JRA-25和NCEP-DOE AMIP-Ⅱ(简称为NCEP-2)再分析资料,采用扩展经验正交分解(EEOF)、相关分析等方法,对比分析了不同资料所揭示的东亚夏季风异常活动的多模态特征,在此基础上探讨了东亚夏季风异常活动各模态对应的大气环流异常分布型及其与中国夏季降水的可能联系。结果表明:(1)四套再分析资料所揭示的东亚夏季风异常活动均存在三种差异显著的空间模态,且各套资料对东亚夏季风异常活动空间多模态特征具有很好的一致性,仅NCEP-2的结果与其他资料略有差异。(2)第一模态体现了夏季风年际异常在中国南方和北方的反相变化,并具有显著的3～6年和准8年周期;与正(负)时间系数相对应,850 hPa风场、500 hPa高度场、SLP均显示东亚沿岸存在从西北太平洋经过日本以南到达鄂霍次克海的“-+-”(“+-+”)经向三极型结构;相应的降水变化在长江中下游为显著的负(正)异常,而在我国东北东部、东南沿海及云南西部则为正(负)异常。(3)第二模态反映了夏季风活动主导模态的一致性变化且在1993年左右发生年代际转折,并呈现准12年周期的强弱交替分布。当对应的时间系数为正(负)时,850 hPa风场在环贝加尔湖地区受强大的异常反气旋(气旋)控制;500 hPa高度场上,中高纬地区表现为异常的纬向波列结构,具体表现为起源于欧洲大陆西部经西西伯利亚平原向东南方向延伸至东北亚地区的“+-+”(“-+-”)的波列;SLP在我国大陆主要为正(负)异常,东亚夏季风整体减弱(加强);对应的夏季降水异常场呈现“南涝北旱”(“南旱北涝”)的分布形势。(4)第三模态表明了夏季风异常活动的东西反相变化,且有12～16年的准周期变化。对应正(负)的时间系数,115°E 以东地区盛行异常偏南(北)风,而115°E 以西地区主要盛行异常偏北(南)风;500 hPa高度场、SLP均显示出东亚沿岸地区、鄂霍次克海至日本以南洋面的“-+”(“+-”)波列以及欧亚大陆北部的准纬向遥相关波列;夏季降水在我国大部分地区偏多(偏少),显著变化主要位于黄淮及附近地区。 相似文献