Analysis On Terrain Decomposition And Distribution Rule Of Meteorological Elements

Terrain has a significant effect on the spatial and temporal distribution of meteorological elements, and it also has different influence on precipitation under different relief scale. It has been shown that the accuracy of weather forecast and early warning and the meshing algorithm of meteorological elements not only depends on the smallest unit of relief scale, but also depends on the local distribution rule of quantitative meteorological elements. The concept of terrain decomposition is presented by this paper. Decomposing the DEM data as geographical signal is meaningful since it provides different components. In addition,combined with relief amplitude and the method of geomorphologic classification, various terrain conditions represented by different components have been recognized. By the precipitation data of ground meteorological station, the variation of spatial scales between windward slopes and leeward slopes is confirmed in different regions,which helps distinguish the significant impact of different spatial scales on precipitation,and the quantitative description of precipitation differences between windward slopes and leeward slopes is completed.Aiming at the problems above, the paper mainly studied:(1) Based on Empirical Mode Decomposition (EMD), the basic concept and algorithm of terrain decomposition are addressed so that 10 components of terrain decomposition are computed. In addition, the technical difficulties of how to use EMD in two-dimensional DEM terrain decomposition is solved.(2) According to the relief amplitude calculated by different decomposition components, geomorphologic classification is determined by reasonable index system. The results indicates that the relief scale information contained in terrain decomposition are different under different geomorphologic conditions. Rolling terrain is reflected in component r2, small and medium relief mountains in R4, and high relief mountains in r6.(3) Using average precipitation data from ground meteorological station, the change rules of terrain decomposition components between windward slopes and leeward slopes is computed, which shows that the effects of slope on precipitation are influenced by geomorphology as much as by the wet and dry conditions. Finally,the effects of slopes of all typical relief mountains on precipitation is described and its quantitative expression is quantified.