Sensitivity of flow dynamics and orographic precipitation to changing ambient conditions in idealised model simulations
Sensitivity of flow dynamics and orographic precipitation to changing ambient conditions in idealised model simulations
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理想化模型模拟中流动动力学和地形降水对环境条件变化的敏感性
DOI：
10.1127/0941-2948/2011/0221
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发表时间：
2011
影响因子：
1.2
通讯作者：
S. Wassermann
中科院分区：
文献类型：
--
作者：
S. Wassermann
理想化的数值模拟使用的非静力学天气预报模式的小尺度模拟（COSMO）在三维（3D）配置进行了调查的环境条件，流动特征和地形降水模式之间的关系。通过改变风速、静稳定度、温度和相对湿度等模型输入参数，考虑了从条件不稳定流到上游减速流的不同流动效应。结果表明，潜热释放显着延迟的发病流动停滞，这可以理解使用湿稳定性的概念。然而，由于饱和和非饱和层的垂直变化，它是不可能的应用这一概念来确定重力波。干燥率（表示上游水汽通量转化为降水量）和降水最大值的位置在一定程度上可以用饱和无量纲山高M{sub m} = N{sub m}H/U来描述，其中H是山高，N{sub m}是饱和稳定度，U是无扰动风速。在绕流制度，降水最大值与扩展重力波，并位于下游的山顶。随着直接山体溢流的增加（减小M{sub m}），降水最大值转移到波峰上游的位置。当M{sub m}变为虚值时，从纯层状降水到嵌入对流的转变突然发生，表明条件不稳定。（orig.）
Idealised numerical simulations using the non-hydrostatic weather prediction model of the Consortium for Small-scale Modeling (COSMO) in a three-dimensional (3D) configuration were conducted to investigate the relationship between ambient conditions, flow characteristics, and orographic precipitation patterns. By changing the model input parameters of wind speed, static stability, temperature, and relative humidity, different flow effects from conditionally unstable flow to upstream deceleration are considered. It is shown that latent heat release significantly delays the onset of flow stagnation, which can be understood using the moist stability concept. However, due to the vertical variations of saturated and unsaturated layers, it is not possible to apply this concept for determining gravity waves. Both the drying ratio, expressing the conversion of the upstream moisture flux into precipitation, and the location of the precipitation maxima can be described to a certain extent by the saturated nondimensional mountain height, M{sub m} = N{sub m}H/U, where H is the mountain height, N{sub m} is the saturated stability, and U is the undisturbed wind speed. In the flow around regime, the precipitation maxima are associated with the extended gravity wave and are located downstream of the mountain crest. With increasing direct mountain overflow (decreasing M{sub m}), the precipitation maxima are shifted to a location upstream of the crest. The transition from purely stratiform precipitation to embedded convection occurs abruptly when M{sub m} becomes imaginary, indicating conditional instability. (orig.)