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1.
对流层上层定常波异常遥相关型的维持机制 总被引：1，自引：0，他引：1
用ＥＣＭＷＦ１９８０－１９８８年的资料和主成份分析方法研究了北半球冬季定常波月平均异常的空间结构和时间变化，分析了对应主要异常型的由辐散风和瞬变涡度通量的异常引起的涡度源异常，并用正压模式研究了涡度源异常在这些异常型维持中的作用。结果表明，瞬变的涡度通量辐合的异常有抵消辐散风所产生的涡度源异常的趋势；单独考虑辐散风异常作为强迫所产生的环流异常与遥相关型的结构和强度相差很大，但如果将瞬变涡度通量辐合的异常也包含到强迫源中，则强迫出来的环流异常会有很大改善 相似文献
2.
辐散风和瞬变的涡度通量的异常对定常波年际异常的强迫作用 总被引：2，自引：4，他引：2
研究了１９８２／１９８３年１２—２月对流层上层由辐散风和瞬变的涡度通量所产生的涡度源异常对定常波异常的强迫作用。结果表明，瞬变的涡度通量辐合的异常有抵消或耗散辐散风产生的涡度源异常的趋势；定常波的异常是在这两种强迫力的共同作用下维持的。同时还表明，对１９８２／１９８３年的情况，热带和赤道中东太平洋上的涡度源异常以及中纬度北太平洋上的涡度源异常都对太平洋／北美地区的大气环流异常起了重要的作用。 相似文献
3.
冬季一次引发华北暴雪的低涡涡度分析 总被引：5，自引：0，他引：5
利用NCEP FNL 1°×1°再分析资料和WRF模式,模拟了2010年1月2～3日我国华北地区的一次由涡旋造成的冬季降雪过程,并采用位涡和涡度方程对引发暴雪的涡旋发展机制进行了诊断分析。结果表明,这次降雪过程中,对流层中层高空浅槽东移、加深及发展,并引导低空和地面系统自西向东移动,高空位涡的下传强迫加强了对流层中低层涡旋的发展。平均通量和涡旋区域的辐合、辐散作用对涡旋涡度的增长贡献最大,扰动通量和类倾斜项的作用较小。在中层涡旋成熟期,环境场的风速小于中层涡旋的移动速度时,环境场相对于涡旋区域为辐散,涡旋涡度减小;当环境场风速大于涡旋的移动速度时,环境场相对于涡旋区域为辐合,涡旋涡度增加。在涡旋衰减期,向涡旋外输送的绝对涡度通量使得涡旋涡度逐渐减弱。这次过程中,高空位涡强迫、低空辐合和涡旋边界平均气流对扰动涡度的输送是涡旋发展的主要机制。 相似文献
4.
利用1980—2018年ERA-Interim全球再分析资料,对汉江上游汉中地区暴雨过程纬向风场及瞬变波活动Eliassen-Palm(下简称EP)通量特征进行诊断分析。结果表明:(1)尝试将瞬变波EP通量特征分析应用到汉江流域典型暴雨过程动力特征研究中,天气尺度瞬变波EP通量的辐散可以表征天气尺度扰动的强迫作用,根据热成风原理,角动量和热量的沉积耗散会进一步影响纬向环流的变化。大气中高层瞬变波活动特征可作为提前量反映汉江流域暴雨的发生。(2)暴雨发生前,30°N附近200 hPa有纬向风减速中心,对应200 hPa为EP通量辐散区,EP通量辐散区扩展加强有利于暴雨的发生,这种大气波动的垂直分布特征及其变化对暴雨发生有指示意义。 相似文献
5.
夏季沿亚洲副热带西风急流Rossby波传播及其与我国降水异常的联系 总被引：1，自引：0，他引：1
利用1960—2015年夏季(6—8月)NCEP 2.5°×2.5°全球逐日再分析资料,采用涡度源方程和Eliassen-Palm通量,对夏季沿亚洲副热带西风急流Rossby波活动的波源、能量传播及其与我国降水异常的关系进行了分析和研究。结果表明:夏季200 hPa大气准静止行星波产生的源地主要集中在地中海地区,亚洲副热带西风急流(ASWJ)中的准静止Rossby波在此激发并沿急流向东传播,东传过程中在急流轴南侧波流相互作用相对活跃。波作用通量的辐合辐散中心沿副热带西风急流交替分布,波流相互作用是ASWJ上西风强弱交替变化的动力机制。沿ASWJ交替分布的五个波作用通量辐合辐散关键区散度具有较强的关联性,表现为同一Rossby波列的不同部分,其中波源处Rossby波动能量的传播对其下游ASWJ的强弱影响最大,而急流关键区内纬向风的大小也与波作用通量散度场的强弱和分布密切相关。波源处以及位于我国青藏高原东部至黄土高原上空的波作用通量散度指数WFD-Ⅰ和WFC-Ⅱ与我国南、北方降水相关性较为显著,在WFD-Ⅰ为正异常年时,对应南方关键区降水偏多年份占比为62.5%,在WFD-Ⅰ为负异常年时,对应北方关键区降水偏多年份占比为80%;在WFC-Ⅱ为正异常年时,对应南方关键区降水偏少年份占比为66.7%,在WFC-Ⅱ为负异常年时,对应北方关键区降水偏少年份占比为81.8%。研究夏季波源处WFD-Ⅰ异常年导致我国降水异常的环流成因发现,WFD-Ⅰ为正异常年时,由上游波源地区激发的Rossby波向下游地区的能量频散偏强,位置偏南,波流相互作用导致我国南方上空高空急流加强,高低空辐散辐合配置加强,垂直上升运动增强,易造成我国南方地区降水异常偏多。WFD-Ⅰ为负异常年时,Rossby波能量的经向传播较强而纬向传播较弱,北方降水关键区受波通量辐散控制,高空西风急流加强,高低空辐散辐合配置和垂直上升运动增强,有利于我国北方地区降水的发展。 相似文献
6.
利用1958～1997年NCEP/NCAR一日四次的风场再分析资料,系统地分析了季节平均西风角动量（即u角动量）经向、垂直输送通量及其三个分量（平均经圈环流、定常波、瞬变涡输送通量）的气候特征,特别是讨论了12～2月、6～8月它们与东、西风带、副热带西风急流、极夜急流之间的联系。结果表明:（1）包含纬度因子的角动量通量与动量通量在高纬地区存在显著差别,高纬对流层上部的强动量输送中心在角动量通量中不明显。而u角动量强经向输送主要在中低纬对流层顶附近和冬半球高纬平流层顶附近,副热带西风急流和极夜西风急流均位于u角动量强向极输送中心及其高纬一侧的辐合区中。（2）发现三个输送分量对急流维持的作用随纬度、季节不同。北半球冬季（夏季）的副热带西风急流主要由平均经圈环流（强度相当的定常波和瞬变涡）强经向输送及辐合维持;南半球西风急流全年均由平均经圈环流和瞬变涡旋输送及辐合维持;冬半球中平流层极夜急流主要由定常波、瞬变涡旋输送及其辐合共同维持。（3）热带东风区是牵连角动量（即Ω角动量）的高值区,它主要由平均经圈环流向对流层上部输送;冬半球副热带及中纬西风区存在u角动量垂直输送的切变区,它主要由平均经圈环流和瞬变涡旋完成;热带对流层顶附近有u角动量的定常波弱向下输送。 相似文献
7.
利用1980-2018年ERA-5全球再分析资料，对汉江流域汉中地区典型暴雨发生前纬向风场变化及天气尺度瞬变波活动(Eliassen-Palm通量特征)进行分析。结果表明：瞬变波EP通量特征分析为汉江流域暴雨潜势预报提供一个有利的参考指标；暴雨发生前，33°N附近200hPa附近有纬向风减速中心，对应200hPa为EP通量辐散区，这种垂直分布模型是暴雨前期有利形势，随着纬向风减速趋势加强，EP通量辐散区扩展并加强，有利于暴雨的发生；7月较之8月，暴雨强度更强、暴雨范围更广、纬向风变化更明显、200hPa以上EP通量辐散更强。若简单地将盛夏暴雨整体进行研究，会影响对不同月份瞬变波活动及大气环流变化趋势的诊断，造成诊断偏差且难以准确反映瞬变波与暴雨的联系。因此在讨论盛夏季天气尺度瞬变波与对流层环流的相互作用时，应针对不同月份分开进行讨论。 相似文献
8.
一次暴雨的湿位涡分析及EVAD技术应用 总被引：10，自引：8，他引：2
利用NCEP/NCAR再分析资料和实测资料对2004年6月24-25日的一次江苏暴雨过程进行了分析,并且根据湿位涡守恒原理和倾斜涡度发展理论,对这次暴雨过程中的湿位涡进行了诊断分析,结果表明:此次暴雨由中尺度低涡、切变线直接触发产生;西南低空急流的稳定维持为这次暴雨的发生提供了重要的水汽条件;当负湿位涡向上的扰动高度增加、强度增强,高低空正负湿位涡区配合较好时常会出现强降水.另外,利用EVAD技术由多普勒雷达基数据定量计算了这次过程的平均散度场,通过分析其演变情况,发现:低层散度场由辐散逐渐向辐合过渡、高层散度场由辐合逐渐向辐散过渡时,预示着强降水将要发生,如果出现相反的变化趋势,则降水减弱或停止;低层由辐散向辐合、高层由辐合向辐散的转折出现时间早于强降水出现的时间,对强降水产生有预示作用,对预报员准确作出短时临近预报预警具有重要实际应用价值. 相似文献
9.
利用1980—2015年ERA-5全球再分析资料,对汉中地区典型暴雨发生前纬向风场变化及天气尺度瞬变波活动(Eliassen-Palm通量特征)进行分析。结果表明:瞬变波Eliassen-Palm(EP)通量特征分析为汉江流域暴雨潜势预报提供一个有利的参考指标;暴雨发生前,33°N附近200 h Pa有纬向风减速中心,对应200 hPa为EP通量辐散区,这种垂直分布模型是暴雨前期的有利形势,随着纬向风减速趋势加快,EP通量辐散区扩展并加强,有利于暴雨的发生;与8月相比,7月暴雨强度更强,暴雨范围更广,纬向风变化更明显,200 hPa的EP通量辐散更强。若简单地将盛夏暴雨整体进行研究,会影响对不同月份瞬变波活动及大气环流变化趋势的诊断,造成诊断偏差且难以准确反映瞬变波与暴雨的联系。因此在讨论盛夏季天气尺度瞬变波与对流层环流的相互作用时,应按月份讨论。 相似文献
10.
定常辐散场产生的涡源和定常波能量传播 总被引：1，自引：0，他引：1
根据ECMWF1980～1988年的全球资料，确定了南北两半球对流层上层定常的辐散风所形成的定常涡源的位置、定常波能量传播路径及它们的位置关系，讨论了涡源的形成机制。由此揭示了热带西太平洋积云对流加热、风暴路径上的潜热释放、欧亚大陆冷源及青藏高原热力和动力作用等主要外源在冬夏南北半球定常波形成中的作用。 相似文献
11.
THE FORCING OF ANOMALOUS DIVERGENT WIND AND TRANSIENT VORTICITY FLUXES TO THE ANOMALY OF STATIONARY WAVES 
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下载免费PDF全文 The forcing of anomalous divergent wind and transient vorticity fluxes to the anomaly ofstationary waves of DJF (December—January—February) 1982/1983 is studied.The results showthat the anomaly of the transient vorticity flux convergence tends to cancel or dissipate the anomalyof the vorticity sources generated by divergent wind.The stationary wave anomalies are maintainedby both of these forcings.It is also found that,for the DJF 1982/1983 case,both of the vorticitysource anomaly over the tropical and equatorial eastern Pacific and that over the midlatitude NorthPacific are important to maintain the atmospheric circulation anomaly over the Pacific/NorthAmerica region. 相似文献
12.
The spatial structure and temporal variations of the stationary wave anomalies in the uppertroposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980—1988 and PCA(principal component analysis)method.The vorticity source anomalies of the mainteleconnection patterns are analyzed,and their roles in the maintenance of the stationary waveanomaly teleconnection patterns are investigated with the harotropic model.The results show thatthe anomalies of transient vorticity flux convergences tend to cancel the anomaly of vorticitysources generated by divergent winds.The stationary wave anomaly patterns caused by divergentwind anomalies only are very different from observations.However,if the anomalous transientvorticity flux convergences are also included in the vorticity sources,the simulated patterns will begreatly improved. 相似文献
13.
In this paper, the dynamical effects of divergent wind on the intraseasonal variability of atmospheric circulation over East Asia are analyzed by using the function of Rossby-wave source and the energy exchanging function be-tween divergent component and rotational component of the flow.The results analyzed from the observed data show that the advection of vorticity by divergent wind caused by the heating due to the monsoon rainfall in the south to the Yangtze River and the strong convective activities around the Philippines may play an important role in the northward jump of westerly jet stream during the seasonal transition from spring circulation to summer circulation over East Asia. Due to the northward movement of the advection of vorticity by the divergent wind, the energy transformation from divergent component into rotational component can be caused over the Yellow River basin and Northwest China and will cause the intensification of the zonal flow there. Thus, the jet stream abruptly shifts northward to North China.Moreover, the analysed results also show that the advection of vorticity by divergent wind caused by the heating due to the strong convective activities around the Philippines also plays an important role in the intraseasonal varia-bility of the circulation over East Asia during the seasonal transition from summer to winter. With the southward movement of the advection of vorticity by the divergent wind, the energy transformation from divergent component into rotational component can be caused over East Asia, especially over the Yangtze-Huaihe River basin. Therefore, the jet stream gradually moves southward from North China to the Yangtze River basin. 相似文献
14.
宋玉成，黄荣辉ＴｈｅＤｙｎａｍｉｃａｌＥｆｆｅｃｔｓｏｆＤｉｖｅｒｇｅｎｔＷｉｎｄｏｎｔｈｅＩｎｔｒａｓｅａｓｏｎａｌｖａｒｉａｂｉｎｔｙｏｆｔｈｅＥａｓｔＡｓｉａｎＣｉｒｃｕｌａｔｉｏｎ￥ＳｏｎｇＹｕｃｈｅｎｇａｎｄＨｕａｎｇＲｏｎｇｈｕｉ（Ｉｎｓ... 相似文献
15.
Connection between the Silk Road Pattern in July and the following January temperature over East Asia 下载免费PDF全文
下载免费PDF全文 This study investigates a cross-seasonal influence of the Silk Road Pattern (SRP) in July and discusses the related mechanism. Both the reanalysis and observational datasets indicate that the July SRP is closely related to the following January temperature over East Asia during 1958/59–2001/02. Linear regression results reveal that, following a higher-than-normal SRP index in July, the Siberian high, Aleutian low, Urals high, East Asian trough, and meridional shear of the East Asian jet intensify significantly in January. Such atmospheric circulation anomalies are favorable for northerly wind anomalies over East Asia, leading to more southward advection of cold air and causing a decrease in temperature. Further analysis indicates that the North Pacific sea surface temperature anomalies (SSTAs) might play a critical role in storing the anomalous signal of the July SRP. The significant SSTAs related to the July SRP weaken in October and November, re-emerge in December, and strengthen in the following January. Such an SSTA pattern in January can induce a surface anomalous cyclone over North Pacific and lead to dominant convergence anomalies over northwestern Pacific. Correspondingly, significant divergence anomalies appear, collocated in the upper-level troposphere in situ. Due to the advection of vorticity by divergent wind, which can be regarded as a wave source, a stationary Rossby wave originates from North Pacific and propagates eastward to East Asia, leading to temperature anomalies through its influence on the large-scale atmospheric circulation. 相似文献
16.
Variability patterns of Rossby wave source 总被引：1，自引：0，他引：1
Mar��lia Harumi Shimizu Iracema Fonseca de Albuquerque Cavalcanti 《Climate Dynamics》2011,37(3-4):441-454
Rossby waves (RW) propagation due to a local forcing is one of the mechanisms responsible for wave trains configurations known as teleconnections. The term teleconnection refers to anomalies patterns that are correlated in several regions of the world, causing large-scale changes in atmospheric waves patterns and temperature and precipitation regimes. The aim of teleconnections studies is to provide a better understanding of atmospheric variability and their mechanisms of action in order to identify patterns that can be tracked and predicted. The purpose of this study was to characterize seasonal and spatial variability of atmospheric RW sources. The RW source at 200?hPa was calculated for the four seasons with reanalysis data of zonal and meridional wind. In the Northern Hemisphere (NH), the RW sources were located on East Asia, North America, North Atlantic and Pacific. The main RW sources in the Southern Hemisphere (SH) were located over Intertropical, South Pacific, South Atlantic and South Indian Convergence Zones. Extratropical regions were also identified, mainly to the south of Australia. The vortex stretching term (S1) and the advection of absolute vorticity by the divergent wind (S2) were analyzed to discuss the physical mechanisms for RW generation. In the NH, the source at East Asia in DJF changed to a sink in JJA, related to the dominance of S1 term in DJF and S2 term in JJA. In the SH, the vortex stretching term had the dominant contribution for RW source located to the south of Australia. The main forcing for RW sources at east of Australia was the advection of absolute vorticity by divergent flow. Over South America, both terms contributed to the source in DJF. The main modes of RW source variability were discussed by using empirical orthogonal functions analysis. RW variability was characterized by wave trains configurations in both hemispheres over regions of jet streams and storm tracks, associated with favorable and unfavorable areas for RW generation. 相似文献
17.
Summary Lower tropospheric (1000–500) hPa kinetic energy (KE), temporal variations of KE and nonlinear KE transfer of rotational and divergent flows and energy conversion between them, partitioning further into stationary and transient components in the Fourier spectral domain and the mechanism for the evolution of significant transient waves for the month July 1979 in the latitudinal belt 10° S–30° N are studied.Divergent zonal and eddy KE show their maxima at the lowest level 1000 hPa. Lower tropospheric monsoon motion provides a non-divergent level close to 850 hPa. The daily flow patterns bear little resemblence to the climatology over tropics at 500 hPa. Although the transient mode of synoptic scale waves is stronger than that of planetary scale waves they are comparable. Analysis of energetics over global tropics can get signature of transient activities embedded in the large scale system. Summer momentum flux in the lower troposphere is essentially associated with stationary planetary and transient synoptic scale waves. Waves 1, 3 and 6 are the most preferred transient waves. Divergent to rotational KE conversion is the most dominating mechanism for the maintenance of planetary and synoptic scale waves. All categories of waves contribute towards the maintenance of zonal flows. The primary source of energy for transient synoptic scale waves is the transient divergent rotational KE transfer whereas the interaction between zonal stationary and transient wave is likely to be secondary source. Transient KE and all transient interactions, stationary KE and all stationary interactions are found to be strongest at 500 hPa and 850 hPa respectively. Growth and decay of transient waves 1 and 3 are mainly controlled by divergent-rotational KE conversions whereas those of transient wave 6 are controlled by KE transfer due to zonal-wave interaction.With 13 Figures 相似文献
18.
The physical effects of topography and heat sources on the formation and maintenance of the summer mon-soon over Asia we discussed in this paper by using the transformed Eularian-mean equations and a quasigeostrophic 34-level spherical coordinate model.The computed results of the divergence of the E-P flux, the induced meridional circulation and the pertur-bation geostrophic wind speed induced by the forcing of topography and heat sources show that the diabatic heating effect over the Tibetan Plateau may play an important role for the formation and maintenance of the summer monsoon over Asia, which is much greater than the dynamical effect of topography.The computed results also show that, of the physical effects of topography and heat sources on the formation and maintenance of the summer monsoon over Asia, the effect of forced meridional circulation is larger than that of the divergence of E-P flux of the induced waves. 相似文献