Urban Boundary-Layer Stability and Turbulent Exchange during Consecutive Episodes of Particle Air Pollution in Beijing, China

Meteorological conditions for severe foggy haze episodes over north China in 2016–2017 winter

“…Owing to the weak radiation [31][32][33] during foggy haze episodes, the averaged near surface air temperature was smaller during pollution development-maintenance periods than during pollution dissipation periods. The relative humidity was usually larger during air pollution development-maintenance periods [3,25]. In this study, there were 8 out of 10 pollution episodes (the 2ed-7th and 9th-10th episodes) that had larger mean relative humidity, and 6 of them showed a difference of mean relative humidity over 10% between pollution development-maintenance and dissipation periods.…”

“…Numerous studies investigated the pollution emission and transportation episodes together with the corresponding meteorological conditions in North China [7][8][9][10][11][12], and they found out the favorable meteorological conditions for haze events include low surface wind [4,13], low planetary boundary layer height [14][15][16][17], high relative humidity [18][19][20], strong temperature inversion [20][21][22][23], high pressure ridge, and much subsidence [23][24]. It was also implied that stable planetary boundary layer is conducive to the formation of haze [14,16,25]. In addition, the characteristics of the terrain in North China also play an important role.…”