NUMERICAL EXPERIMENTS OF INFLUENCE OF TOPOGRAPHY ON ATMOSPHERIC MOTION

A 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 mounrain height and shape, stratification and basic inflow have influence on downslope winds and large-amplitude 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.