Quarterdiurnal tide in the middle atmosphere (QuarTA)

太阳潮汐及其变化强烈地决定着中层和低热层的动力学。潮汐分量之一是四分之一日潮汐（QTD），偶尔在电离层零星E参数和雷达以及少数卫星观测中报告。虽然全日、半日和半日潮汐分量的分析比较频繁，但QDT得到的关注要少得多，主要是由于它的振幅较小，这使得观测更加困难。为了填补这一空白，将在Quarta中详细分析QDT及其强迫机制。将利用流星雷达风，特别是利用德国科尔姆的长期数据集，结合其他北方半球雷达观测，分析MLT动力学中的潮汐特征。QDT的全球结构将通过GPS无线电掩星获得的零星E发生率并辅以电离层观测来分析。这些观测结果将由雷达观测到的风切变和数值模拟得出的结果加以解释。为了深入了解QDT的强迫机制，我们将使用一个中层大气的机械环流模式，它包括非线性相互作用过程以及辐射强迫。在敏感性实验中，不同的强迫机制将被单独或组合地关闭。在Quarta中，通过将本地和全球观测与数值模拟相结合，我们期望能够更深入地了解QDT的全球结构及其强迫过程，这些尚未得到足够详细的分析。

The dynamics of the mesosphere and lower thermosphere (MLT) is strongly determined by solar tides and their variability. One of the tidal components is the quarterdiurnal tide (QTD), which has occasionally been reported in ionospheric sporadic E parameters and radar and few satellite observations. While the diurnal, semidiurnal, and also terdiurnal tidal components have been analyzed more frequently, the QDT hast attained much less attention, mainly owing to its smaller amplitudes, which makes observations more difficult. To fill this gap, within QuarTA the QDT and its forcing mechanisms will be analyzed in detail. The characteristics of the tide in MLT dynamics will be analyzed using meteor radar winds, in particular making use of the long-term data set at Collm, Germany, in combination with other Northern Hemisphere radar observations. The global structure of the QDT will be analyzed in sporadic E occurrence rates obtained from GPS radio occultations complemented by ionosonde observations. These observations will be interpreted by wind shear observed by radar and obtained from numerical modelling. To get insight into the forcing mechanisms of the QDT, we shall use a mechanistic circulation model of the middle atmosphere, which includes nonlinear interaction processes as well as radiative forcing. In sensitivity experiments, the different forcing mechanisms will be turned off both separately and in combination. Within QuarTA, from combining local and global observations with numerical modelling, we therefore expect to get more insight into the global structure of the QDT as well as into its forcing processes, which have not yet been analyzed in sufficient detail.