基于logistic曲线识别混合层高度的新方法

A new method to identify mixing layer height based on logistic curve

基于成都市2013年6月至2014年2月Mie散射激光雷达探测数据的分析表明,混合层顶附近大气消光系数自下而上均存在显著下降区、整体缓变区以及二者之间的过渡区.利用logistic曲线对上述变化特征进行拟合,通过计算该曲线曲率最大值对应的高度,据此提出识别混合层高度的新方法.该方法的设计思想符合混合层的定义,即为湍流特征不连续界面以下湍流充分发展的气层;另外,相应的计算结果不仅和探空曲线得到的混合层高度总体一致,也与地面细颗粒物浓度的变化特征保持高度的相关.

Based on the analysis of the Mie scattering lidar in Chengdu from June2013to February2014,it is shown that there are three layers near the top of the mixing layer of the atmospheric extinction coefficient from bottom to top,the significant decreasing layer,the overall slow transformation layer and the transition layer between the two.Using the logistic curve to fit the variation characteristics of the extinction coefficient,a new method to identify the mixing layerheight is proposed by calculating the height of the curve's maximum curvature.The idea of the method accords with the definition of the mixing layer which is below the discontinuous interface of the turbulence characteristics.In addition,the results of the new method are not only consistent with the mixing layer height obtained by sounding curve,but also strongly related to the variation of fine particulate mass concentration.