Retrieval of Boundary Layer Height and Its Influence on PM 2.5 Concentration Based on Lidar Observation over Guangzhou

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Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height (PBLH) over Guangzhou from September 2013 to November 2014 over Guangzhou. Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly. In addition, the PBLH diurnal variations and the relationship between PM_2.5 concentration and PBLH during polluted and clean episodes were studied. Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m. The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were ~1100 m and ~650 m, respectively. The PBLH was significantly lower in the dry season than in the wet season, with the average highest PBLH in the dry season and the wet season being ~1050 m and ~1200 m respectively. Compared to the wet season, the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation. Episode analysis indicated that the PBLH was ~50% higher during clean episodes than during haze episodes. The average highest PBLH in the haze episodes and clean episodes were ~800 m and ~1300 m, respectively. A significant negative correlation between PBLH and PM_2.5 concentration(<i>r</i>=-0.55^**) is discovered.According to China "Ambient Air Quality Standard", the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions, while the corresponding PM_2.5 concentration were ~2-2.5 times higher.