| 强迫流与不稳定流的相互作用 |
| |
| 引用本文： | 程艳红,陆汉城.强迫流与不稳定流的相互作用[J].大气科学,2006,30(4):609-618. |
| |
| 作者姓名： | 程艳红 陆汉城 |
| |
| 作者单位： | 解放军理工大学气象学院大气科学系,南京,211101 |
| |
| 基金项目： | 国家自然科学基金;科技部科研项目 |
| |
| 摘 要： | 通过数值试验的方法,研究非保守系统中的基流平衡被破坏和重建过程中,产生非平衡中尺度环流与不稳定能量造成的对流关系,着重探索在形成持续时间较长、尺度较大的深厚湿对流的物理过程中,强迫与不稳定的相互作用.研究结果表明:强迫流比不稳定流小一个量级.强迫流虽然本身的量值较小,但是强迫流是不稳定流的触发机制.如果环境场具有深厚的不稳定层(垂直或倾斜方向),并且环境场强迫出一定振幅的呈上升运动的强迫流,则在0～3小时以后,将在强迫流上升运动中心激发出不稳定流上升运动中心,或使已经存在的不稳定流上升运动中心向强迫流上升运动中心移动.
|
| 关 键 词： | 强迫流 不稳定流 相互作用 |
| 文章编号： | 1006-9895（2006）04-0609-10 |
| 收稿时间： | 2005-07-28 |
| 修稿时间： | 2005-07-282005-12-24 |
The Interaction Between Forced and Instable Convection |
| |
| CHENG Yan-Hong and LU Han-Cheng.The Interaction Between Forced and Instable Convection[J].Chinese Journal of Atmospheric Sciences,2006,30(4):609-618. |
| |
| Authors: | CHENG Yan-Hong and LU Han-Cheng |
| |
| Institution: | Departmentof Atmospheric Sciences, Instituteof Meteorology, PLA University of Science and Technology, Nanjing 211101 |
| |
| Abstract: | Slantwise convection caused by frontogenesis and moist symmetric instability also can lead to band rain.In virtual atmosphere,it is difficult to separate frontogenesis from moist symmetric instability,because they are associated with each other.In the process of deep moist convection with the characteristics of long duration and large scale,the interaction between forced and instable mesoscale convection become more complex.Based on the numerical method,the interaction between forced and instable convection in the process of the break and rebuilding of equilibrium state is discussed using mesoscale numerical-model output of Meiyu front heavy rain process in China.The instable convection is defined as the convection caused by conditional instability or conditional symmetric instability,and the ascending motion caused by the forced factor except the instable one is named as the forced convection.For moist atmosphere,the atmospheric instable factor is defined by convective condensation heat item.In theory,the ageostrophic omega equation should be used only with convective condensation heat item on the right side of the equation to compute the instable convection.But in practice,the parameterized scheme is used to compute the instable convection,the scheme is not only complex,but also with definite error.The numerical result of sensitivity test is used to resolve the instable convection.There are several kinds of reasons resulting in the forced convection,they are ageostrophic forced effect of atmospheric motion,terrain,environmental thermodynamic force and friction.The whole forced convection caused by all factors could not be computed accurately.So the mesoscale circumfluence caused by ageostrophic force is just considered,the ageostrophic omega equation only with ageostrophic force is used to compute the force convection.The MM5 mesoscale simulation system is chosen to make a numerical experiment for a typical Meiyu-front process standing from 23 to 24 June 1999.Three experiment schemes are designed.In the first scheme,the virtual Meiyu-front process is used as the control experimentation.In the second scheme,the initial atmospheric instability is enlarged,and no change has been made for other factors.In the third scheme,only the initial atmospheric instability is reduced.By using the second and third schemes as sensitivity experiments,the first as control experiment,the computation method is built for the numerical resolution of the instable convection,and the reciprocity of forced and instable convection is discussed.A conclusion is drawn about the interaction of the forced convection and instable convection.The quantity of instable convection is ten times of that of forced convection.If the deep instability in vertical or slantwise direction and the finite-amplitude ascending motion in the forced convection are given,the instable convection will appear in three hours after the production of forced convection,or if the instable convection exists before the production of forced convection,the existing convection center will move to the forced convection center.On the contrary,if the finite-amplitude forced convection caused by ambient field shows the descending motion or the weak ascending motion,it makes against the creation of the instable convection,and the relevant ascending motion centre could not be created in the actual vertical speed field.So whether ambient field can excite ascending motion to improve the instable energy release,and whether the layer of instable status shown in the ambient filed is thick are two key factors whether instable energy release causes instable convection.Instable status shown in the ambient field could not insure the instable convection to create strong deep moist convection.The forced convection is trigger mechanism of the instable convection. |
| |
| Keywords: | interaction forced convection instable convection |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《大气科学》浏览原始摘要信息 |
| 点击此处可从《大气科学》下载免费的PDF全文 |
|
