Three-dimensional numerical study of cell broadening during cold-air outbreaks
Three-dimensional numerical study of cell broadening during cold-air outbreaks
复制标题
冷空气爆发期间细胞展宽的三维数值研究
DOI：
10.1007/bf02430333
复制
发表时间：
1996
影响因子：
4.3
通讯作者：
A. Chlond
中科院分区：
文献类型：
--
作者：
G. Müller;A. Chlond
本文用三维数值模拟方法研究了冷空气爆发时边界层发展和对流型转变。模拟包括二次流过渡开始与相对较小规模的边界层卷发展过程中的初始阶段和中尺度细胞对流模式结束。计算网格的应用，其水平网格大小能够分辨率的小尺度的初始模式，其域的大小是足够大，以捕捉中尺度对流模式，超载，甚至国家的最先进的超级计算机。为了绕过计算机存储问题，模式域的水平尺寸和计算网格的水平分辨率被调整到占主导地位的对流结构的尺度。这使得对流单体的水平尺度增加到超过初始modeldomain.The模型的大小的值的模拟被施加到ARKTIS 1991年实验期间观察到的冷空气爆发的条件。模型揭示了所观察到的情况的最重要的特征。进行敏感性研究，以调查细胞增宽和各种物理过程之间的关系。人工切断液态水的形成，防止了对流尺度的扩大。由于凝结，特别是辐射云顶冷却的潜热加热被确定为导致单元加宽的过程。我们提出了一个概念模型，阐明了云顶冷却可能产生较大的长宽比的机制。
The boundary-layer development and convection-pattern transition typically occurring in cold-air outbreaks is studied using three-dimensional simulations. The simulations include the secondary-flow transition starting with the relatively small-scale boundary-layer rolls developing during the initial phase and ending with mesoscale cellular convection patterns. The application of a computational grid, whose horizontal mesh size enables the resolution of the small-scale initial patterns and whose domain size is large enough to capture mesoscale convection patterns, overcharges even state-of-the-art supercomputers. In order to bypass the computer storage problem, the horizontal size of the model domain and the horizontal resolution of the computational grid are adjusted to the scale of the dominant convective structures. This enables the simulation of convection cells whose horizontal scales increase up to values exceeding the size of the initial model domain.The model is applied to conditions of a cold-air outbreak observed during the ARKTIS 1991 experiment. The most important characteristics of the observed situation are revealed by the model. Sensitivity studies are performed in order to investigate the relation between cell broadening and various physical processes. The artificial cutoff of liquid-water formation prevents the enlargement of convective scales. Latent heating due to condensation and especially radiative cloud-top cooling are identified as processes leading to cell broadening. We propose a conceptual model that elucidates the mechanism by which cloud-top cooling may generate larger aspect ratios.