地形对于气流运动影响的数值研究

NUMERICAL EXPERIMENTS OF INFLUENCE OF TOPOGRAPHY ON ATMOSPHERIC MOTION

建立了二维、非静力平衡的数值模式，研究地形对上游气流的阻挡以及大振幅背风波谷与下坡风的形成。结果表明：地形的阻挡效应受地形高度、大气层结及地形非对称性等因子的影响。数值试验与理论分析都证明地形越高、层结越稳定时阻挡作用越强；同样条件下，迎风坡坡度大的地形容易对气流形成阻挡。此外，分析了地形高度、大气层结、地形非对称性以及基本入流大小对背风波谷及下坡风强度影响的规律，并通过一次实际观测对数值模拟结果进行了检验。

two-dimensional, nonhydrostatic numerical model is designed to examine the blocking phenomenon in upstream side of topography and large-amplitude mountain wave trough and downslope winds in the downstream side. It's indicated that the topography blocking effects are affected by the factors such as mountain height, stratification and asymmetry of mountain profile. Numerical experiments and theoretical analysis show that the blocking usually occurs when the mountain is higher and stratification is much more stable. It also favourably occurs when the mountain upstream side is much steeper. In addition, the mountain height and shape. stratification and basic inflow have influence on downslope winds and largeuamplitude wave trough in the lee side. The processes are studied with a case on 11 January, 1972. It's shown that the large-amplitude trough and intense downslope windstorm are liable to be induced by higher mountain with steeper slope on lee side when stratification is more stable and inflow is more intense.