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1.
PNA流型的年际变化及温、热带太平洋海温的作用 总被引：3，自引：0，他引：3
本文分析了PNA型环流的年际变化和影响因子,发现它存在两种优势周期振荡:一种是3—5年的振荡,另一种是10年左右的振荡.研究表明,前者与赤道太平洋海温的主要振荡周期相对应(同相关系),后者与北太平洋海温的主要振荡周期一致(反相关系).揭示了PNA型环流的变化与北太平洋海温比与赤道太平洋海温具有更密切的联系.并且由于北太平洋海温影响的频带与赤道太平洋海温的不同,它的作用有时与赤道太平洋海温的同相,有时则反相,使得ENSO与太平洋-北美地区大气环流和气候异常的关系变得复杂化.指出当考虑北太平洋海温的共同作用后 相似文献
2.
This study examines the PNA associated atmospheric diabatic heating by linearly isolating the influence of ENSO. The analysis
is based on the NCEP–NCAR and ERA-40 reanalyses and a 1,000-year-long integration of the CCCma coupled climate model. Both
the vertically integrated and three-dimensional diabatic heating are examined. The Rossby wave sources in association with
the PNA are also diagnosed. The PNA-related heating is confined outside the tropics and is dominated by anomalies in the eastern
Pacific, with a north–south dipole structure in mid-latitudes and the northern subtropics. The heating anomalies change sign
with height in mid-latitudes but have the same sign throughout the troposphere in the northern subtropics. Relatively weak
heating anomalies also appear in mid-latitudes, downstream of the heating dipole over North America and the western North
Atlantic. The heating anomalies are largely supported by the advections related to the mean state throughout the troposphere,
and partially damped by the advections related to the eddy effect, particularly at the upper troposphere over the North Pacific.
Broadly similar patterns are seen from the NCEP–NCAR and ERA-40 reanalyses. Yet anomalous heating centers are generally located
at relatively lower troposphere for the ERA-40 with respect to the NCEP–NCAR. The tropical heating anomalies are rather weak,
remarkably different from those related to ENSO variability. In addition, the Rossby wave source collocates with the atmospheric
diabatic forcing in the mid-high latitudes over the PNA sector, and shows no forcing source in the tropics. The results demonstrate
possible forcing in the mid-high latitudes, regardless of tropical heating for the PNA teleconnection. The modeled heating
and wave forcing anomalies in association with the modeled PNA compare reasonably well with the reanalysis-based estimates,
increasing confidence in the observational results. The analysis provides further evidence of the independence of the PNA
on ENSO from the diabatic heating point of view. 相似文献
3.
Reconstruction of Conceptual Prediction Model for the Three Rainfall Patterns in the summer of eastern China under global warming 总被引：1，自引：0，他引：1
With the influence of global warming,the global climate has undergone significant inter-decadal variation since the late 1970s.Although El Nio-Southern Oscillation(ENSO)has been the strongest signal for predicting global climate inter-annual variability,its relation with the summer rainfall in China has significantly changed,and its indicative function on the summer rainfall in China has weakened.This has led to a significant decrease in the accuracy rate of early conceptual prediction models for the Three Rainfall Patterns in the summer of eastern China.On the basis of the difference analysis of atmospheric circulation system configuration in summer,as well as the interaction of ocean and atmospheric in previous winter between two phases,i.e.before and after the significant global warming(1951 to 1978 and 1979 to 2012,respectively),we concluded that(1)Under different inter-decadal backgrounds,the atmospheric circulations that impacted the Three Rainfall Patterns in the summer of eastern China showed consistency,but in the latter phase of the global warming,the Western Pacific Subtropical High(WPSH)was on the strong side,the position of which was in the south,and the blocking high in the Eurasia mid-high latitudes was active,while the polar vortex extended to the south,and meridional circulation intensified.This circulation background may have been conducive to the increase of the circulation frequency of Patterns II and III,and the decrease of the circulation frequency of Pattern I,thus leading to more Patterns II and III and fewer Pattern I in the summer rainfall of eastern China.(2)In the former phase,the corresponding previous winter SST fields of different rainfall patterns showed visible differences.The impact of ENSO on North Pacific Oscillation(NPO)was great,and the identification ability of which on Patterns I and II of summer rainfall was effective.In the latter phase,this identification ability decreased,while the impact of ENSO on the Pacific/North American(PNA)teleconnection pattern increased,and the identification ability of the PNA on Patterns II and III also increased.Based on the new inter-decadal climate background,this study reconstructs the conceptual prediction model for the Three Rainfall Patterns in summer of eastern China by using the previous winter PNA and the Eurasian(EU)teleconnection indexes.The fitting effect was satisfying,though it is necessary to be further tested. 相似文献
4.
This study uses multiple sea surface temperature(SST) datasets to perform a parallel comparison of three super El Ni os and their effects on the stratosphere. The results show that, different from ordinary El Ni os, warm SST anomalies appear earliest in the western tropical Pacific and precede the super El Ni o peak by more than 18 months. In the previous winter,relative to the mature phase of El Ni o, as a precursor, North Pacific Oscillation-like circulation anomalies are observed. A Pacific–North America(PNA) teleconnection appears in the extratropical troposphere during the mature phase, in spite of the subtle differences between the intensities, as well as the zonal position, of the PNA lobes. Related to the negative rainfall response over the tropical Indian Ocean, the PNA teleconnection in the winter of 1997/98 is the strongest among the three super El Ni os. The northern winter stratosphere shows large anomalies in the polar cap temperature and the circumpolar westerly, if the interferences from other factors are linearly filtered from the circulation data. Associated with the positive PNA response in a super El Ni o winter, positive polar cap temperature anomalies and circumpolar easterly anomalies,though different in timing, are also observed in the mature winters of the three super El Ni os. The stratospheric polar vortex in the next winter relative to the 1982/83 and 1997/98 events is also anomalously weaker and warmer, and the stratospheric circulation conditions remain to be seen in the coming winter following the mature phase of the 2015/16 event. 相似文献
5.
Investigation is carried out of winter Northern Hemisphere (NH) 100 hpa teleconnection, indicating the existence of a PNA pattern whose wavetrain well resembles that at 500 hpa level. During the climax of the EI Nino episode (winter), the 100 PNA becomes strong, a fact that manifests itself more clearly than at the 500 hpa level. Moreover, study is made of the anomaly in the tropical monthly windfield and mean circulation on a seasonal basis in a range of phases of the EI Nino event. Results show that the 100 hpa geopotential height is lowered on a large scale in the spring and previous winter with the event happening as compared to a La Nina year, wherewith diagnosis is performed of the 1991/1992 EI Nino episode. 相似文献
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7.
利用全国160站1951—2008年11月温度、降水资料和同期秋季NCEP/NCAR 500 hPa高度场再分析资料,分析了我国东部季风区11月暖湿、暖干、冷湿、冷干年同期环流特征,并对同期、前期环流特征进行了差异t检验。结果表明:暖型 (冷型) 同期环流对应乌拉尔山阻塞高压不明显 (明显),欧亚中高纬度地区盛行纬向 (经向) 环流;干型 (湿型) 同期环流对应西太平洋副热带高压偏弱 (强)、偏东 (西)。差异t检验分布特征表明:在亚洲中高纬度地区,暖干、冷湿型 (暖湿、冷干型) 同期环流主要表现为南北 (东西) 气压场的差异;暖干、冷湿型的前期和同期环流特征分别具有EU (Eurasia) 和反EU遥相关距平结构,而暖湿、冷干型前期和同期环流特征分别具有反PNA (Pacific/North American) 和PNA遥相关距平结构。 相似文献
8.
本文应用统计方法讨论6～11月的准PNA型,得到如下结论: 秋季,低纬中太平洋热源异常,能发出位置与PNA型相类似的遥相关型——准PNA型。这种遥相关型呈二维Rossby波列,具有相当正压结构,在西风带中沿固定波导向极向东传播,从而影响中太平洋和北美天气。 夏季,由于热源位置的差异,则不存在与PNA型相类似的遥相关型。从而认为热源的扰动在遥相关型的成因上起着举足轻重的作用。 相似文献
9.
清华大学地球系统科学研究中心在一个标准耦合模式（SC）的基础上建立了交互集合耦合模式系统（IE）,该系统可以实现多个不同大气模式或者同一大气模式采取不同初值组成的多个分量集合之后与海、陆、冰模式进行耦合.本文利用同一大气模式七个不同初值分量与其它模式分量开展在线集合耦合试验,利用积分稳定之后100年的试验结果,分析了IE在减小海-气界面大气噪音的情况下,对北太平洋海表面温度（SST）变率和ENSO的模拟,并与SC模拟结果进行了对比.分析表明,IE减小了北太平洋中高纬度SST方差的85%以上,表明该区域SST变率主要受大气的影响,且主要是通过改变海表湍流热通量实现的.黑潮延伸体区和北太平洋中部副热带涡旋区域平均SST 8年左右的低频周期主要受来自大气内部动力过程的驱动.在集合耦合模拟中,无论是副热带涡旋区SST与ENSO的联系,还是ENSO与北太平洋中高纬度SST的联系都能模拟出来,而标准模式未能模拟出这些现象,意味着大气噪音过强将掩盖ENSO与太平洋热带外SST的联系.IE对与ENSO关联的“太平洋-北美”（PNA）遥相关型的合理模拟,并通过湍流热通量对海表温度的影响,是其能够更好模拟ENSO与北太平洋中高纬度SST关系的重要原因.本文通过分析验证了所建立的交互集合耦合模式系统的合理性,揭示了该系统在海-气相互作用研究领域方面具有一定应用前景. 相似文献
10.
研究了北半球１００ｈＰａ冬季遥相关现象，指出，北半球冬季１００ｈＰａ存在ＰＮＡ流型，它的波列与５００ｈＰａ流型很接近，当厄尔尼诺发展到盛期（冬季）时，１００ｈＰａ出现强ＰＮＡ型，这种对应关系比５００ｈＰａ好些，此外，还研究了厄尔尼发生、发展各阶段的１００ｈＰａ低纬风场以及１００ｈＰａ春，夏，秋，冬四季平均环流异常特征，发现在厄尔尼诺发生年春季，１００ｈＰａ高度比反厄尔尼诺年大范围偏低，发生前的冬季 相似文献