中间层和低热层(MLT, Mesosphere and Lower Thermosphere)区域中经常出现的大风场/风场剪切在低层大气与热层和电离层的耦合过程中有重要作用。对大风场/风场剪切的特征和形成机制的研究成为目前大气动力学研究的热点问题。本项目将首先通过分析流星雷达和非相干散射雷达观测的风场资料，提取出背景风场和潮汐分量，研究它们在整个风场/风场剪切中的贡献。然后，我们将利用已经建立的模拟重力波非线性传播过程的二维和三维并行数值模式，分别以经验模式和观测资料给出的背景风场和潮汐作为模式的背景，模拟重力波在不同背景风场和潮汐中的非线性传播情况，研究背景风场、潮汐和重力波以及它们之间的非线性相互作用对大风场/风场剪切的贡献，并探索可能的物理机制。

Large winds/wind shears in the mesosphere and lower thermosphere (MLT) region have been received much attentions in recent years because of their importance in coupling the lower atmosphere and thermosphere/inonsphere. Firstly, we extract the mean wind and tides from the wind data observed by meteor radar and incoherent scatter radar. The contributions of mean wind and tides on the large winds/wind shears will be studied. Secondly, using the parallel model that solves the nonlinear propagation of gravity waves in two- and three-dimensions, we simulate the nonlinear propagation of gravity waves in the background atmosphere that are composed of mean wind and tides obtianed from empirical model and/or observations. Finally, according to the observations and simulation results, we investigate the relative contributions of mean wind, tides, gravity waves, and their nonlinear interactions to the large winds/wind shears. Moreover, the possible mechanisms, which are responsible for the formation of large winds/wind shears, will also be explored.