Simulation of the hierarchy structure in tropical disturbances by a three-dimensional model treating the cloud physical process

热带扰动一般具有层次结构。典型的例子是由1,000 km尺度的超星系团由1,000 km尺度的中尺度对流组成的季内振荡。本研究的目的是模拟这种层次结构的热带扰动，使用模式与山崎的参数化。在此参数化中，对云水、雨水和水蒸气进行了预测，并对中尺度对流进行了明确的解析。热带地区的网格长度可达40公里。因此，我们可以做一个与以往有质的不同的实验。地球表面覆盖着海洋，海洋的温度在纬向上是均匀的，相对于赤道是对称的。在模拟中，赤道附近的对流受到抑制，没有出现超星团；与季节内振荡有关的层次结构没有得到很好的模拟。而ITCZ主要沿10个N和10个S形成，且ITCZ扰动呈层次结构。即尺度在1000公里以上，由100公里尺度的中尺度对流构成。扰动一般向西移动，而中尺度对流几乎是静止的。在这方面，还模拟了层次结构的特点。此外，有人认为这些结果归因于该模型的几个固有效应。在未来，必须进行灵敏度实验。辐射冷却实验尤其重要，因为这影响到静稳定性，而静稳定性又对赤道附近对流的活动和扰动的移动方向有很大的影响。与季节内振荡相关的层次结构可能会在本课程中出现。

Tropical disturbances generally have the hierarchy structure. The typical example is the intraseasonal oscillation in which superclusters having the scale of 1, 000km are composed of mesoscale convection having the scale of lOOkm. The aim of this research is to simulate this hierarchy structure of tropical disturbances, using a model with Yamasaki's parameterization. In this parameterization, cloud water and rainwater as well as water vapor are predicted, and meso-scale convection can be resolved explicitly. The grid length is as fine as 40km in the tropics. Therefore, we can perform a qualitatively different experiment from previous ones. The surface is covered with the ocean whose temperature is zonally uniform and symmetric with respect to the equator.In the simulation, convection near the equator is suppressed and the supercluster does not appear ; the hierarchy structure associated with the intraseasonal oscillation is not well simulated. However, the ITCZ is formed along about 10ﾟN and 10ﾟS, and ITCZ disturbances show the hierarchy structure. That is, their scales are 1, 000km or more, and are composed of meso-scale convection with the scale of 100km. The disturbances generally move westward, while the meso-scale convection is almost stationary. Also in this respect, the characteristics of the hierarchy structure are simulated. Further, it is suggested that these results are attributed to several inherent effects of this model.In the future, sensitivity experiments must be carried out. In particular, an experiment for radiative cooling is important, because this affects the static stability, which in turn has a great influence on the activity of convection near the equator and the moving direction of disturbances. The hierarchy structure associated with the intraseasonal oscillation will probablyappear in this course.