石家庄冬季典型污染过程气溶胶激光雷达观测

Aerosol lidar observation of typical pollution process in Shijiazhuang in Winter

基于2016年冬季石家庄市微脉冲气溶胶激光雷达观测资料,采用归一化梯度法和梯度法两种方法反演了大气污染边界层高度,并将结果与相同时段探空资料获得的边界层高度进行对比验证,同时选取典型个例对污染边界层高度的过程演变特征进行了分析,探索了不同污染等级下污染边界层结构.结果表明,归一化、梯度法反演结果均与探空位温确定的边界层高度存在一致性,相关系数分别为0.62、0.55,均通过了0.05的显著性检验,但归一化相对误差为19%,梯度法为34%,表明归一化梯度法优于梯度法且其反演结果是可靠的.空气质量优良日,归一化梯度法反演结果准确度降低,与位温确定边界层高度最大偏差约1000m;随着污染程度加重,反演结果与位温确定边界层高度差减小,污染期间,污染边界层高度总体低于1000m,污染最重时段降到400m左右.不同空气质量等级、不同高度气溶胶消光系数垂直递减率具有明显差异,污染天气400m高度垂直递减率最大,表明该层以下为较重污染聚积层,之后随高度升高消光系数明显减小,700m以上为清洁空气.

Based on the aerosol observations of the micropulse lidar in Shijiazhuang City in winter 2016,the normalized gradient method and the gradient method were used to invert the atmospheric pollution boundary layer height,and the results were compared with the boundary layer height determined by sounding data in the same period.Typical cases were selected to analyze the process evolution characteristics of the height of the polluted boundary layer,and investigate the structure of the polluted boundary layer at different air quality levels.The results indicate that,the retrievals of these two approaches were consistent with the boundary layer height determined by sounding data and the correlation coefficients were 0.62 and 0.55,which passed the significance test of 0.05.However,the relative error were 19%and 34%indicating that the normalized gradient method was better than the gradient method.When the air quality were Moderate and Good,the accuracy of results was reduced with a maximum deviation of nearly 1000m.As the degree of pollution increases,the difference decreases.During the period of pollution,the height of the pollution boundary layer was generally less than 1000m,and the lowest height was about 400m at the heaviest pollution.The aerosol extinction coefficients of different air quality levels and heights had different vertical decline rates.Maximum vertical decline rate was at 400m height in polluted weather.It indicated that the heavy pollution accumulation layer was below 400m,and then the extinction coefficient decreased significantly with height increased.It was clean air above 700m.