投影寻踪法在建立积雪深度模型上的应用

针对融雪期积雪深度变化问题的高维非线性、非正态特点,利用投影寻踪法将积雪深度变化多指标问题转化为单一投影指标问题,采用遗传算法优化投影方向得出最佳投影值,最终得到对积雪深度变化影响较大的因子,实现在低维空间上反应积雪深度变化的目的。实例分析结果表明:影响积雪深度变化的各因素贡献力依次为:土壤地表温度净辐射空气温度土壤体积含水量风速空气相对湿度降水水汽压。通过建立MLP神经网络积雪深度模型表明:利用投影寻踪法提取的积雪深度主要影响因子是可靠的,且提取的主要影响因子为简化积雪深度模型提供理论依据。

Application of Projection Pursuit Method in Building Snow Depth Model

In the snow melt period, snow depth variation has the features of high dimension, nonlinear and non-normal distribution. In this study, the multi index problem on snow depth change was transformed into the problem of single projection index by the projection pursuit method with optimized the projection direction by genetic algorithm. So the snow depth change dimention has been reduced with the method. The result shows that the factors effect sequence on snow depth dynamic change follows: the ground temperature > net radiation > air temperature > soil moisture > wind speed > relative humidity > total precipitation > vapor pressure. MLP neural network was used to build the snow depth model, which can simulate snow depth. The result shows that using projection pursuit method to get the snow depth of major impact factor is reliable, and major impact factor can simplify the snow depth model.