摘要:边界层高度是影响大气边界层发展和空气污染程度的重要因子，是环境和气候研究的重要参数。本文利用激光雷达对北京地区2011年5月至2012年4月的边界层高度进行探测分析，采用小波协方差方法反演边界层高度，评估了该方法的适用性。得到基于小波协方差方法自动判断边界层高度的最优参数组合，激光雷达与飞机探测结果对比一致性较好；与探空结果相关系数0.88，激光雷达反演的边界层高度略偏高。当激光雷达的垂直分辨率为30 m时，更加适合北京地区的步长和阈值分别为210 m和0.05；当激光雷达的垂直分辨率为15 m时，步长和阈值分别为135 m和0.05。分析期间，不同季节边界层高度日变化有明显的不同，夏季14：00（北京时）左右达到最高，较高的边界层高度可维持3~4 h，平均可达1.30 km；冬季较高边界层高度只能维持2 h左右，平均为1.08 km。有云与无云天气边界层日变化特征以及边界层高度存在显著的差异，云的存在减少了到达地面的直接辐射，抑制了湍流的发展，进一步抑制了边界层的发展；本文也将激光雷达反演边界层高度结果应用于观测时期边界层高度与地面污染的关系研究中，统计得到边界层高度与PM2.5浓度的相关系数为－0.340。
关键词:边界层高度/
小波协方差方法/
激光雷达/
飞机/
探空
Abstract:The planetary boundary layer (PBL) is an important parameter in the studies of environment and climate and it affects air pollution and evolution of atmospheric boundary layer. We analyze PBL heights retrieved using wavelet covariance transform (WCT) method from lidar backscatter profiles data from May 2011 to April 2012 and evaluate the performance of this method. PBL heights are validated using observations of one radiosonde on the ground and airborne instruments for the purpose to optimize the parameters required for lidar detection using the WCT method under different atmospheric conditions. The result shows that the PBL heights have a better agreement between lidar and airborne retrievals than between lidar and radiosonde retrievals with a correlation coefficient of 0.88. Lidar appears to slightly overestimate PBL height. If the vertical resolution of lidar is 30 m, the step length and threshold for Beijing area are 210 m and 0.05, respectively; the step length and threshold are 135 m and 0.05 respectively for the vertical lidar resolution of 15 m. PBL height shows a diurnal variation with an average maximum value of 1.3 km starting from 1400 BT (Beijing time) and lasts for three to four hours in the summer, while the average maximum value of 1.08 km lasts for about two hours in the winter. The result suggests that the direct radiation reaching the ground is reduced by cloud, which depresses the evolution of turbulence and PBL and results in lower PBL height. We also apply the PBL heights retrieved from lidar to the analysis of relationship between the concentration of PM2.5 and meteorological elements for the one-year period. The result shows that the correlation coefficient between PBL height and the concentration of PM2.5 is -0.340.
Key words:Planetary boundary layer (PBL) height/
Wavelet covariance transform method/
Lidar/
Aircraft/
Radiosonde
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