Much attention has been paid to terrain effects on planetary scale. Few works have addressed these impacts at finer
scales. In this study, the terrain effect on a backflow weather occurred over North China during December 22 to 23, 2002
was investigated using the Pennsylvania State University-NCAR Fifth-Generation Mesoscale Model (MM5), version 3.
Numerical simulation results show that the mountains in the western North China play a very important role in the
backflow precipitation. The cold air from North East Plain was obstructed by the Taihang Mountain. The flat topography
of the plain reduced the thickness of the cold air, its vertical velocity, and the intenseness of the precipitation. The results
indicate that the cold air was accumulated in the windward of the mountain. This accumulation resulted in increased
thickness of the cold air. Humid air could climb up to the top and amplify the precipitation.