共查询到20条相似文献，搜索用时 125 毫秒
1.
《大气和海洋科学快报》2021,(3)
平流层准两年振荡(QBO)是赤道平流层(～100-1 hPa)变率的主要模态,可对中高纬地区的环流产生重要影响,但目前利用通用大气环流模式(GCM)对其进行准确模拟仍然是一个挑战.本文利用IAP大气环流模式(IAP-AGCM)的中高层大气模式版本(IAP-AGCML69)对QBO进行模拟,并对其动量收支情况进行分析.研究发现,QBO主要是由对流活动引起的重力波强迫(参数化)引起的,但该动量强迫被平流层赤道上升流所引起的平流过程显著削弱.模式可分辨尺度的波动强迫对赤道上空的QBO的总纬向风倾向有正贡献,在上平流层,其量值大小与参数化的重力波强迫相当.以上结果提供了对QBO形成机制以及模式模拟差异可能原因的认识. 相似文献
2.
3.
4.
热带准两年振荡影响北半球冬季大气环流的诊断分析 总被引：11，自引：3，他引：8
利用NCEP/NCAR再分析资料,首先讨论了热带纬向风准两年振荡(QBO)的东、西风位相的划分标准.结果发现,赤道50 hPa的风与西风深厚度关系最密切,即赤道50 hPa的纬向平均风为西(东)风时往往代表平流层下层为一层深厚的西(东)风.在此基础上诊断分析了1958/1959～1997/1998年共40个冬季中热带纬向风QBO对北半球中高纬度地区纬向平均环流和准定常行星波传播的影响.诊断分析表明,热带QBO对北半球冬季大气环流的影响主要表现在平流层和对流层上层.热带QBO的东风位相年与西风位相年相比,中高纬地区的绕极西风环流明显减弱,中低纬地区则出现相反变化,从而在平流层的纬向平均环流分布上呈现偶极子形式.纬向平均流的这种年际变化可以很好地用中高纬度准定常行星波传播的异常加以解释,QBO的东风位相年和西风位相年相比,中高纬准定常行星波向极地的传播更强,从而在高纬度平流层产生异常的E-P通量辐合,波-流相互作用的结果使得西风减弱.但是热带纬向风QBO的影响在1958/1959～1997/1998年的前后20年有所差异.后20年相对于前20年而言,东西风位相的差异有所减小,Hol-ton-Tan振荡明显减弱;就行星波传播而言,东风位相年下,前20年行星波向上传播较弱,而后20年则以大约70°N为分界点,以南向上传播较强,以北向上传播较弱.这种差异可能跟中高纬度纬向西风的自身变化有关. 相似文献
5.
6.
北半球冬季行星波的传播及其输运作用 总被引：20，自引：0，他引：20
利用变换欧拉平均方程讨论了行星波动力学。观测和模拟结果都表明,在北半球冬季准定常行星波的经向传播存在两支波导。一支为高纬度波导,另一支则为低纬度波导。这些结果与理论分析相当一致。通过对EP通量进一步的研究表明,平流层爆发性增温是沿高纬度波导传播的异常行星波与平均气流相互作用的结果。而热带风场的准两年周期振荡（QBO）是低纬度平流层下层大气纬向平均流的一个重要年际变化,它可以影响行星波沿低纬度波导的传播;此外,由一个行星波一平均流耦合模式模拟的结果表明,这个热带风场的变化还可以通过波流相互作用调制行星波沿高纬度波导的传播。 行星波对臭氧的输运作用在文中也进行了分析。行星波强迫出的剩余平均环流表明,耗散的行星波有强的输运作用;向北的涡动热量输送可以强迫出一个正的输运环流,其在低纬度上升并在高纬度下沉。同时研究还表明,热带风场的QBO对行星波传播的调制对输运环流也有重要影响,模式结果表明,在QBO的东风位相期间行星波引起的输运作用明显增强,其结果可用于解释平流层高纬度臭氧的年际变化。 相似文献
7.
在以赤道低平流层纬向风垂直切变为依据划分平流层QBO位相的基础上，讨论了赤道低平流层纬向风QBO与对流层环流及东亚季风的关系。结果表明：强冬季风和弱夏季风对应着赤道低平流层纬向风的东风切变位相，强夏季风和弱冬季风对应着赤道低平流层西风切变位相，赤道低平流层纬向风QBO对对流层环流有一定影响，冬春季节平流层与对流层的相互作用比夏秋季节明显。 相似文献
8.
热带平流层臭氧准两年周期振荡的特征及数值模拟 总被引：19，自引：1，他引：19
利用HALOE的观测资料、对热带地区平流层臭氧垂直分布的年际变化及其准两年周期振荡（QBO）进行研究，并同赤道上空平均的纬向风场的准两年周期振荡进行了模拟研究。资料分析结果表明，平流层臭氧浓度高值区的位置在南北方向上和垂直方向上的有明显的准两年周期，臭氧浓度高值中心的南北移动和上下移动又引起局地臭氧总量的周期性变化和准两年周期振荡南北半球不对称。而臭氧浓度中心位置的准两年周期变化与赤道上空平均纬向风的准两年周期振荡密切相关。资料分析还表明，赤道上空平流层中臭氧浓度QBO的位相随高度变化多次。模拟试验表明，纬向风QBO引起垂直经圈环流的变化，在平流层有三对余差环流圈。它们对O3在不同纬度和高度的输送是引起O3准两年周期振荡的重要动力原因。其中，余差环流在平流层中层（25－35km)的环流圈起着重要的作用。 相似文献
9.
利用变换欧拉平均方程讨论了行星波动力学，观测和模拟结果都表明，在北半球冬季准定常行星波的经向传播存在两支波导。一支为高纬度波导，另一支则为低纬度波导。这些结果与理论分析相当一致。通过对EP通量进一步的研究表明，平流层爆发性增温是沿高纬度波导传播的异常行星波与平均气流相互作用的结果。而热带风场的准两年周期振荡（QBO）是低纬度平流层下层大气纬向平均流的一个重要年际变化，它可以影响行星波沿低纬度波导的传播；此外，由一个行星波－平均流耦合模式模拟的结果表明，这个热带风场的变化还可以通过波流相互作用调制行星波沿高纬度波导的传播。行星波对臭氧的输运作用在中也进行了分析，行星波强迫出的剩余平均环流表明，耗散的行星波有强的输运作用；向北的涡动热量输送可以强迫出一个正的输运环流，其在低纬度上升并在高纬度下沉。同时研究还表明，热带风场的QBO对行星波传播的调制对输运环流也有重要影响，模式结果表明，在QBO的东风位相期间行星波引起的输运作用明显增强，其结果可用于解释平流层高纬度臭氧的年际变化。 相似文献
10.
大气重力波是一种普遍存在于大气层中的波动现象,与多种不同尺度天气现象均有密切联系,研究平流层重力波的时空分布特征及其可能影响机制对于全球大气环流、大尺度气候变化和各类中尺度天气系统的研究具有重要意义.利用基于PANGAEA数据中心提供的2002—2015年逐月平流层重力波参数资料和SPARC数据中心提供的1992—1997年逐月纬向风资料,分析了平流层重力波参数的时空分布特征,并讨论了影响平流层重力波变化的可能机制.结果表明,对于重力波参数的纬向平均分布,平流层重力波扰动温度和垂直波长随高度增加而增大,而水平波数和绝对动量通量则相反.在夏半球的中低纬度和冬半球的高纬度存在重力波参数的大值区,在赤道附近全年存在重力波参数的低值区.平流层重力波参数水平分布表现为纬向上的带状分布,强度随季节发生变化.在相同纬度,重力波参数的大值中心出现在大陆,特别是山脉地区.平流层纬向风和重力波参数二者的分布具有一致性,说明背景风对大气的扰动是影响重力波参数的可能机制之一. 相似文献
11.
《大气和海洋科学快报》2021,14(3):100021
The quasi-biennial oscillation (QBO), a dominant mode of the equatorial stratospheric (~100–1 hPa) variability, is known to impact tropospheric circulation in the middle and high latitudes. Yet, its realistic simulation in general circulation models remains a challenge. The authors examine the simulated QBO in the 69-layer version of the Institute of Atmospheric Physics Atmospheric General Circulation Model (IAP-AGCML69) and analyze its momentum budget. The authors find that the QBO is primarily caused by parameterized gravity-wave forcing due to tropospheric convection, but the downward propagation of the momentum source is significantly offset by the upward advection of zonal wind by the equatorial upwelling in the stratosphere. Resolved-scale waves act as a positive contribution to the total zonal wind tendency of the QBO over the equator with comparable magnitude to the gravity-wave forcing in the upper stratosphere. Results provide insights into the mechanism of the QBO and possible causes of differences in models.摘要平流层准两年振荡 (QBO) 是赤道平流层 (~100–1 hPa) 变率的主要模态, 可对中高纬地区的环流产生重要影响, 但目前利用通用大气环流模式 (GCM) 对其进行准确模拟仍然是一个挑战.本文利用IAP大气环流模式 (IAP-AGCM) 的中高层大气模式版本 (IAP-AGCML69) 对QBO进行模拟, 并对其动量收支情况进行分析.研究发现, QBO主要是由对流活动引起的重力波强迫 (参数化) 引起的, 但该动量强迫被平流层赤道上升流所引起的平流过程显著削弱.模式可分辨尺度的波动强迫对赤道上空的QBO的总纬向风倾向有正贡献, 在上平流层, 其量值大小与参数化的重力波强迫相当.以上结果提供了对QBO形成机制以及模式模拟差异可能原因的认识. 相似文献
12.
根据1953～1991年赤道平流层纬向风资料分析,得出我国东部地区7月份主要雨带位置与赤道平流层30～50 hPa平均纬向风准两年振荡（以下简称赤道平流层QBO）有较好的关联。在西风位相条件下,我国7月主要雨带位置较偏北;在东风位相条件下,我国7月主要雨带位置易偏南。它们之间的关系主要是通过对对流层环流的影响相联系的。利用赤道平流层纬向风的变化规律并结合冬季北太平洋对流层环流特征,对我国7月主要雨带类型的预报,有一定实用意义。 相似文献
13.
The momentum flux of stratospheric gravity waves generated by Typhoon Ewiniar (2006) is examined using a Weather Research and Forecasting (WRF) model. In the stratosphere, zonal momentum flux with a positive sign by eastward-propagating waves is significant during the northward moving of the typhoon, while both zonal and meridional momentum fluxes with positive signs are significant during the typhoon decaying stage in which the typhoon moves northeastward. The magnitude of the momentum flux is greater during the mature stage of the typhoon than the decaying stage, and the phase speeds of the dominant momentum flux are less than 30 m s?1 with a peak at 10–16 m s?1. Positive momentum flux decreases with height overall in the stratosphere for both zonal and meridional components. The resultant gravity-wave drag forcing plays a role to decelerate the easterly background wind in the stratosphere. This drag forcing is relatively large above z = 40 km and below z = 20 km, and lower stratospheric wave drag is expected to affect the typhoon dynamics by modifying the background wind shear and inducing the secondary circulation in the troposphere. 相似文献
14.
低平流层准两年变率研究 总被引：6，自引：2，他引：4
分析ＮＣＡＲ／ＮＣＥＰ４０年分析资料得出,赤道低平流层纬向风年际变率的平均周期约２８．２个月,最大振幅的２０ｈＰａ,西（东）风距平平垂直下传平均速度１．２１（１．０４）ｋｍ／月。用１０ｈＰａ和７０ｈＰａ月平均纬向风标准化距平之差反映整层准两年变率的相位。低平流层两半球中纬气温有与之配合的振荡,西（东）风切变时,中纬气温偏低（高）。赤道纬向风准两年变率引起的经圈环流异常是联系低续续向风与中纬气温准年 相似文献
15.
16.
Mauro Dall’Amico Lesley J. Gray Karen H. Rosenlof Adam A. Scaife Keith P. Shine Peter A. Stott 《Climate Dynamics》2010,34(2-3):381-398
In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979–2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend. 相似文献
17.
赤道低平流层纬向风垂直切变与ENSO变率的关系 总被引：1，自引：0，他引：1
利用NCEP／NCAR 40a再分析资料研究了赤道低平流层纬向风垂直切变与ENSO变率间的关系。结果得出，赤道低平流层纬向风的垂直切变呈现明显的准两年振荡，SOI和Nino3区SSTA的准两年周期成分与赤道低平流层纬向风垂直切变分别呈现反位相和同位相关系。赤道低平流层西（东）风切变位相时，OLR、1000hPa高度，2000hPa高度和温度、850hPa温度等要素的距平分布与其在El Nino(La Nina)时段的分布相似。 相似文献
18.
A zonal-vertical two-dimensional equatorial model is used to study the possibility that the long period oscillation of the zonal mean flow occurring in the lower equatorial stratosphere (QBO) is caused by local thermal ac-tivities at the tropical tropopause. The model successfully reproduces QBO-like oscillations of the zonal mean flow, suggesting that the local heating or cooling at the tropical tropopause is probably the main reason of QBO’s genera-tion. The analysis of the dependence of the oscillation on the wave fencing indicates that the oscillation is not sensible to the forcing scale. The model can reproduce QBO-like oscillations with any forcing scale if the fencing period and amplitude take appropriate values, proving that the internal gravity waves generated by local thermal source take much important roles in QBO. 相似文献
19.
Observations have shown that the monsoon is a highly variable phenomenon of the tropical troposphere, which exhibits significant variance in the temporal range of two to three years. The reason for this specific interannual variability has not yet been identified unequivocally. Observational analyses have also shown that EI Niño indices or western Pacific SSTs exhibit some power in the two to three year period range and therefore it was suggested that an ocean-atmosphere interaction could excite and support such a cycle. Similar mechanisms include land-surface-atmosphere interaction as a possible driving mechanism. A rather different explanation could be provided by a forcing mechanism based on the quasi-biennial oscillation of the zonal wind in the lower equatorial stratosphere (QBO). The QBO is a phenomenon driven by equatorial waves with periods of some days which are excited in the troposphere. Provided that the monsoon circulation reacts to the modulation of tropopause conditions as forced by the QBO, this could explain monsoon variability in the quasi-biennial window. The possibility of a QBO-driven monsoon variability is investigated in this study in a number of general circulation model experiments where the QBO is assimilated to externally controlled phase states. These experiments show that the boreal summer monsoon is significantly influenced by the QBO. A QBO westerly phase implies less precipitation in the western Pacific, but more in India, in agreement with observations. The austral summer monsoon is exposed to similar but weaker mechanisms and the precipitation does not change significantly. 相似文献
20.
The quasi-biennial oscillation (QBO) in the zonal wind in the tropical stratosphere is one of the most predictable aspects of the circulation anywhere in the atmosphere and can be accurately forecast for many months in advance. If the stratospheric QBO systematically (and significantly) affects the tropospheric circulation, it potentially provides a predictable signal useful for seasonal forecasting. The stratospheric QBO itself is generally not well represented in current numerical models, however, including those used for seasonal prediction and this potential may not be exploited by current numerical-model based forecast systems. The purpose of the present study is to ascertain if a knowledge of the state of the QBO can contribute to extratropical boreal winter seasonal forecast skill and, if so, to motivate further research in this area. The investigation is in the context of the second Historical Forecasting Project (HFP2), a state-of-the-art multimodel two-tier ensemble seasonal forecasting system. The first tier, consisting of a prediction of sea surface temperature anomalies (SSTAs), is followed by the second tier which is a prediction of the state of the atmosphere and surface using an AGCM initialized from atmospheric analyses and using the predicted SSTs as boundary conditions. The HFP2 forecasts are successful in capturing the extratropical effects of sea surface temperature anomalies in the equatorial Pacific to the extent that a linear statistical correction based on the NINO3.4 index does not provide additional extratropical skill. By contrast, knowledge of the state of the stratospheric QBO can be used statistically to add extratropical skill centred in the region of the North Atlantic Oscillation. Although the additional skill is modest, the result supports the contention that taking account of the QBO could improve extratropical seasonal forecasting skill. This might be done statistically after the fact, by forcing the QBO state into the forecast model as it runs or, preferably, by using models which correctly represent the physical processes and behaviour of the QBO. 相似文献