Publication Date:
2016-12-08
Description:
To investigate regional haze formation, ceilometer observations at the Beijing (BJ), Shijiazhuang (SJZ), Tianjin (TJ) and Qinhuangdao (QHD) stations were conducted from October 12 to November 11, 2014, to obtain the boundary layer height (BLH) and the attenuated backscattering coefficients (ABC). Particles at the four stations were highly correlated, whereas precursors of particles exhibited weaker correlations. By analyzing the typical haze episode between October 21and 26, 2014, we found that warm advection at a height of 850 hPa from the Loess Plateau caused a gradual decline in the regional BLH. Moreover, water vapor transported from the southern NCP caused the column water vapor amount to increase from 0.015 kg m -2 to 0.042 kg m -2 in the boundary layer in BJ. As southerly transport prevailed during the transition period, ABC profiles in the BJ, TJ and QHD stations showed a bilayer pattern, and the second layer was between 500 and 1000 m. As a result, the ABC integrations of BJ and TJ increased by 74.2 and 139.7 %, respectively. During the polluted period, due to the weakened transport effect, the ABC integrations of the four stations decreased by 7.9, 18.2, 16.2 and 28.2 %, respectively. Contributions of the secondary inorganic species (sulfate, nitrate and ammonium) at BJ increased from 37.3 % to 56.9 %, and the mean particle size increased from 107.8 nm to 140.8 nm. Emissions in southern NCP should be mitigated during the transition period, whereas the inorganic precursors are the most important air pollutants during the polluted period.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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