Triple charge-coupled device cameras combined backscatter lidar for retrieving PM2.5 from aerosol extinction coefficient
Jing Gao, Jie Pan, Jingjing Wang, Yangjian Cai, Yuefeng Zhao
Abstract
The vertical aerosol extinction coefficient profile is the key to evaluating the aerosol radiation effect. In addition, it is also the premise of indirect inversion of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">M</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> concentration from the lidar signal. A novel lidar system combining tripe charge-coupled device (CCD) cameras and backscatter lidar is proposed to retrieve accurately the aerosol extinction coefficient. The relative humidity segmentation method is used to convert the aerosol extinction coefficient into <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">M</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> concentrations. The results show that the combination of triple CCDs and backscatter lidar can obtain a wider-range extinction coefficient profile. The variation trend of fitted <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">M</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> concentrations and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">M</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> concentrations measured by the in situ instrument show a high correlation. The correlation coefficient reaches 0.850.