Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

Abstract

Abstract. The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China) project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties, including the scattering coefficient (σ sp ), the hemispheric back scattering coefficient (σ bsp ), the absorption coefficient (σ ap ), as well as the single scattering albedo (ω), are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σ sp, 550nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm −1 , respectively. The average σ ap for the two periods is respectively 47±38 and 43±27 Mm −1 . The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σ sp and σ bsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of σ sp , σ ap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better under-

A parameterization of low visibilities for hazy days in the North China Plain

“…The high aerosol surface and volume concentrations also confirm the aerosol polluted status. This has also been demonstrated by Ma et al (2011), in which high average scattering coefficients (σ sp,550 nm ) of 874±282 Mm −1 were observed during two heavily polluted episodes in 2009 summer. The effective aerosol radii were mainly distributed in the range of 105∼437 nm, with a mean value of 192 nm.…”

An Investigation of Aerosol Scattering and Absorption Properties in Wuhan, Central China

“…This value was lower than the value of 0.826 reported in Guangzhou [14], 0.88 at SDZ, 0.81 in summer Beijing [41], 0.82 in spring at the Wuqing site [21], and 0.81 in Shanghai [26]. The low SSA can reflect high loading of absorbing aerosols.…”

“…The σ and σ increased until reaching the night peak and maintained high between 1:00 LZT and 7:00 LZT. This situation can be attributed to that stable nocturnal PBL formation leading to low atmospheric aerosol diffusion after sunset (18:00 LZT), and pollutants were bounded in the shallow PBLH to result in higher aerosol concentrations at the surface [21,22,26]. At the same time, the phenomenon of aerosol dry deposition can also enhance the concentration of aerosols at night.…”

“…The values of SSA increased from 7:00 LZT to 13:00 LZT, indicating that light absorption aerosols such as BC dissipated faster than light scattering particulates. Some studies reported that the noon peak could have resulted from the breakout of a large number of secondary aerosols due to the photochemical reactions of gaseous precursors and the increased loading of light-scattering aerosols at noon [8,18,21,26].…”

“…In China, the rapid growth of economic and urbanization construction has led to heavy emissions of anthropogenic pollutants in recent decades. To thoroughly understand the aerosol radiative forcing characteristics in China, numerous surface aerosol experiments have been conducted [17][18][19][20][21][22][23]. However, most of these studies have been conducted in the Beijing-Tianjin-Hebei region [5,15,18,[21][22][23], the Pearl River Delta [14,17,24,25], the Yangtze River Delta [26] and the northwest semi-arid areas [27][28][29].…”