Numerical simulation of orographic rainbands
Numerical simulation of orographic rainbands
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地形雨带的数值模拟
DOI：
10.1029/2002jd001593
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发表时间：
2003
影响因子：
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通讯作者：
S. Cosma
中科院分区：
文献类型：
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作者：
S. Anquetin;Fabien Minsicloux;J. Creutin;S. Cosma
[1] 这项研究基于模拟暖雨事件和雷达数据的统计分析，旨在强调导致地势组织浅层对流的主要物理机制。调查地区塞文山脉-维瓦莱 (Cevennes-Vivarais) 位于法国东南部。塞文山脉实验（1986-1988 年秋季）的雷达图像揭示了降雨分布的特征性和重复性结构，该结构以狭窄的带状或羽流形式组织，在静止的南风地中海流的情况下，其方向为南北向。 1986 年 11 月 14 日的事件已被选择并构成本次数值研究的数据集。这项工作与 Miniscloux 等人之前的工作密切相关。 [2001] 详细介绍了从塞文实验数据库提取的雷达数据集的地质统计分析结果。主要结果强调了降雨模式的物理特征和动态。继 Cosma 等人最近的工作之后。 [2002]，高分辨率（Δ = I km）模拟继续使用非静水三维（3D）大气模型 MesoNH，以重现在 Ceveunes 地区观测到的雨带。数值模型正确地再现了雨带的结构和动力学。地统计分析已应用于模拟雨场。模型稍微高估了雨带内雨团向北的平流速度（观测为75 km h -1 ，而观测为60 km h -1 ），并且模拟雨带在N 180°方向上比观测雨场更窄、更有组织性。通过比较可以对数值方法的选择和物理参数化的真实性进行限定和验证。 3D 模拟场的分析证实了 Cosma 等人所证明的负责降雨组织的物理机制。 [2002]通过理想化模拟。统计分析强调了低层辐合带下存在平均地形特征，该低层辐合带由一系列东西向的山脊和贯穿的山谷组成。雨带产生于这些地形特征的上游，并由于障碍物周围的水流偏转及其渗透到山谷中所产生的汇聚而在背风处增强。模拟触发发生在比观察到的触发更靠南的地方，并且一旦模型中适当地描述了地形，触发就会激活。
[1] This study, based on a statistical analysis of simulated warm rain event and radar data, aims at highlighting the main physical mechanisms that lead to organize shallow convection on the relief. The region of investigation, the Cevennes-Vivarais, is located in the southeast part of France. Radar images from the Cevennes experiment (fall 1986-1988) reveal a characteristic and repetitive structure of the rain distribution organized in narrow bands or plumes, oriented south-north in the case of stationary southerly Mediterranean flow. The event of 14 November 1986 has been selected and constitutes the data set of this numerical study. This work is closely associated with the previous work by Miniscloux et al. [2001] which presents in detail the results of a geostatistical analysis of the radar data set extracted from the Cevennes experiment data base. The main results highlight the physical characteristics and the dynamics of the rain patterns. Following the recent work of Cosma et al. [2002], high-resolution (Δ = I km) simulations have been continued with the nonhydrostatic three-dimensional (3D) atmospheric model MesoNH, in order to reproduce the observed rainbands over the Ceveunes region. The numerical model correctly reproduces the structure and the dynamics of the rainbands. The geostatistical analysis has been applied for the simulated rain fields. The model slightly overestimates the northward advection velocity of the rain cells within the bands (75 km h -1 against 60 km h -1 for the observation), and the simulated rainbands are narrower and more organized around the N 180° direction than the observed rain field. The comparison allows the qualification and validation of the choice of the numerical methodology and realism of the physical parameterizations. The analysis of the 3D simulated fields confirms the physical mechanisms responsible for the rain organization demonstrated by Cosma et al. [2002] through idealized simulations. The statistical analysis highlights the presence of mean topographic features under low-level convergence zones composed of a succession of ridges and penetrating valleys orientated east-west. The rainbands are generated upstream of these topographic features and enhanced on the leeside due to the convergence created by the flow deflection around the obstacle and its penetration into the valleys. The simulated triggering takes place further to the south than the observed one, and the triggering is active as soon as the relief is suitably described in the model.