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首页> 外文期刊>Atmospheric chemistry and physics >Wave fluxes of equatorial Kelvin waves and QBO zonal wind forcing derived from SABER and ECMWF temperature space-time spectra
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Wave fluxes of equatorial Kelvin waves and QBO zonal wind forcing derived from SABER and ECMWF temperature space-time spectra

机译：由SABER和ECMWF温度时空谱推导的赤道开尔文波和QBO纬向风的通量。

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The quasi-biennial oscillation (QBO) of the zonal mean zonal wind is a dynamical phenomenon of the tropical middle atmosphere. Influences of the QBO can even be found at mid and high latitudes. It is widely accepted that the phase descent of alternating tropical easterlies and westerlies is driven by atmospheric waves of both global scale (equatorial wave modes like Kelvin, equatorial Rossby, Rossby-gravity, or inertia-gravity waves), as well as mesoscale gravity waves. However, the relative distribution of the different types of waves to the forcing of the QBO winds is highly uncertain. This is the case because until recently there were no high resolution long-term global measurements in the stratosphere. In our study we estimate Kelvin wave momentum flux and the contribution of zonal wind forcing by Kelvin waves based on space-time spectra determined from both Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature measurements as well as temperatures from European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. Peak values of total Kelvin wave zonal wind forcing found are about 0.2 m/s/day. There is good agreement between SABER and ECMWF results. Altitude-time cross sections are shown and the results are compared to the total wave forcing required to balance the background atmosphere. Sometimes Kelvin wave forcing is sufficient to explain almost the whole total wave forcing required for the momentum balance during the transition from QBO easterly to westerly winds. This is especially the case during the periods of strong westerly wind shear when the zonal wind is between −20 and 10 m/s at the equator in the altitude range 20 to 35 km. During other parts of the phases of strong westerly wind shear, however, the contribution of Kelvin waves can be comparably low and the missing wave forcing, which is often attributed to mesoscale gravity waves or intermediate scale waves, can be the by far dominant contribution of the QBO forcing. It is also found that seasonal variations of Kelvin wave accelerations could play an important role for the maintenance of the QBO westerly wind jets in the lower stratosphere.
机译：纬向平均纬向风的准两年一次振荡（QBO）是热带中层大气的动力学现象。 QBO的影响甚至可以在中高纬度地区发现。普遍认为，热带东风和西风交替的相位下降是由全球范围的大气波（开尔文，赤道罗斯比，罗斯比重力或惯性引力波等赤道波模式）以及中尺度引力波驱动的。但是，不同类型的波浪对QBO风强迫的相对分布是高度不确定的。之所以如此，是因为直到最近，平流层还没有高分辨率的长期全球测量数据。在我们的研究中，我们根据通过宽带发射辐射法（SABER）测得的大气探测声以及欧洲中等温度中心的温度确定的时空频谱，估算开尔文波动量通量和开尔文波对纬向强迫的贡献。 -范围天气预报（ECMWF）运营分析。发现的总开尔文波纬向风强迫的峰值约为0.2 m / s /天。 SABRE和ECMWF结果之间有很好的一致性。显示了高度-时间截面，并将结果与​​平衡背景大气所需的总波浪强迫进行了比较。有时，开尔文波浪强迫足以解释从QBO向东向西风过渡期间动量平衡所需的几乎所有总波浪强迫。在强西风切变期间，当在20至35 km的高度范围内赤道纬向风在-20和10 m / s之间时，尤其如此。然而，在强西风切变的其他阶段，开尔文波的贡献可能相对较低，而通常归因于中尺度重力波或中尺度波的缺失波强迫可能是迄今为止的主要贡献。 QBO强制。还发现开尔文波加速度的季节性变化可能对平流层下层QBO西风气流的维持起重要作用。

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