The Spacing of Orographic Rainbands Triggered by Small-Scale Topography
The Spacing of Orographic Rainbands Triggered by Small-Scale Topography
复制标题
小尺度地形引发的地形雨带间距
DOI：
10.1175/2007jas2335.1
复制
发表时间：
2007
影响因子：
3.1
通讯作者：
G. Bryan
中科院分区：
文献类型：
--
作者：
D. Kirshbaum;R. Rotunno;G. Bryan
摘要采用理想化数值模拟和分析理论相结合的方法，研究了俄勒冈州西部沿海地区对流地形雨带的间距。根据观测到的沿海范围带状降水事件进行的模拟表明，大气对山脊上条件性不稳定流的响应强烈依赖于山脊迎风侧的亚脊尺度地形强迫。当此小尺度地形仅包含单尺度(λ)地形变异性时，波段间距与λ相同，但当同时存在地形尺度频谱时，波段间距范围在5至10公里之间，这一值与观测结果一致。在模拟的基础上，建立了一个无粘线性模式，为理解雨带的尺度选择提供了物理基础。这一分析模式捕捉到了地形云上游背风波的过渡过程。
Abstract A combination of idealized numerical simulations and analytical theory is used to investigate the spacing between convective orographic rainbands over the Coastal Range of western Oregon. The simulations, which are idealized from an observed banded precipitation event over the Coastal Range, indicate that the atmospheric response to conditionally unstable flow over the mountain ridge depends strongly on the subridge-scale topographic forcing on the windward side of the ridge. When this small-scale terrain contains only a single scale (λ) of terrain variability, the band spacing is identical to λ, but when a spectrum of terrain scales are simultaneously present, the band spacing ranges between 5 and 10 km, a value that is consistent with observations. Based on the simulations, an inviscid linear model is developed to provide a physical basis for understanding the scale selection of the rainbands. This analytical model, which captures the transition from lee waves upstream of the orographic cloud t...