Quarterdiurnal tide in the middle atmosphere (QuarTA)

太阳潮汐及其变率在很大程度上决定了中间层和低热层(MLT)的动力学。潮汐分量之一是四日潮(QTd)，在电离层零星E参数和雷达中偶尔会有报道，但很少有卫星观测。虽然对全日、半日和全日潮汐分量的分析比较频繁，但QDT得到的关注要少得多，主要是因为它的幅度较小，这使得观测变得更加困难。为了填补这一空白，将在Quarta内部详细分析QDT及其强迫机制。将利用流星雷达风，特别是利用德国科勒姆的长期数据集，结合其他北半球雷达观测，分析MLT动力学中的潮汐特征。QDT的全球结构将根据全球定位系统无线电掩星和电离层探空仪观测获得的零星E出现率进行分析。这些观测将由雷达观测到的风切变来解释，并通过数值模拟获得。为了深入了解QDT的强迫机制，我们将使用一个包括非线性相互作用过程和辐射强迫的中间大气机制环流模式。在敏感性实验中，不同的强迫机制将分别关闭和组合关闭。因此，在Quarta内部，通过将本地和全球观测与数值模拟相结合，我们期望对QDT的全球结构以及它的强迫过程有更多的洞察，这些过程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.