Study on the quasi-biennial oscillation using a general circulation model.

利用大气环流模式(GCM)研究了赤道低平流层准两年振荡(QBO)。利用CCSR/NIES GCM对QBO进行了数值模拟，从强迫作用的新结果看，重力波对QBO的作用似乎比开尔文波和Rossby重力波更重要。因此，我们利用一个由GCM导出的二维模型来检验重力波对QBO的可能作用。在二维模型中很容易得到类QBO的振荡。然而，振荡的周期太短，大约为100天。这是由于二维模型中的强重力波引起的。第二年，我们用1/5扇区的GCM模型进行了QBO模拟。在平流层水平分辨率为T106，垂直分辨率为1公里，以解决模式中的波动问题。我们在GCM中获得了类QBO振荡，这在世界上尚属首次。然而，与真实的QBO有一些差异，振荡的高度比QBO的高，周期短，大约400天(真正的QBO大约800天)。如上所述，这一结果在世界上是第一次试验。这是使用完整的GCM进行QBO工作的很好的一步。

We investigate the quasi-biennial oscillation (QBO) in the equatorial lower stratosphere using a general circulation model (GCM). The CCSR/NIES GCM is used.From the new result about the forcing to the QBO, it seems that gravity waves are more important to the QBO than Kelvin wave and Rossby-gravity wave. So we tested the possible role of the gravity wave to the QBO using a two-dimensional model which derived from the GCM.A QBO-like oscillation is easily obtained in the two-dimensional model. However, the period of the oscillation is too short, about 100 days. It is due to strong gravity wave in the two-dimensional model. It is because the model is two-dimensional and no-rotation.In the second year, we performed the QBO simulation using the GCM which is 1/5 sector model. The horizontal resolution is T106 and vertical resolution is 1km in the stratosphere in order to resolve the wave in the model. We have obtained a QBO like oscillation in the GCM.It is the first result in the world. However, there are some discrepancies to the real QBO.The height of the oscillation is higher than that of the QBO.The period is short, about 400 day ( about 800 days in the real QBO ).As mentioned above, this result is first trial in the world. It is a great step to the QBO work using a full GCM.