Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

Abstract

This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean number of HDs were 68.7 and 4.9 days for the Sichuan-Basin (SCB) and the rest of SCC region, respectively. The seasonally averaged HDs over SCB reached its maximum in winter (34.7 days), followed by autumn (17.0 days) and spring (11.6 days), and with the minimum observed in summer (5.5 days). The inter-annual variations of HDs in 18 main cities revealed that Zigong, Neijiang, and Yibin, which are located in the southern of SCB, have been the most polluted areas over the SCC region in the past decades. A notable increasing trend in annual HDs over the majority of SCC region was found during 1980–1995, then the trend sharply reversed during 1996–2005, while it increased, fluctuating at some cities after 2006. Seasonally, the increased trend in spring and autumn seems to be the strongest during 1980–1995, whereas the decreased trend in spring and winter was stronger than other seasons during 1996–2005. In addition, a remarkable increasing trend was found in winter since 2006. Using correlation analysis between HDs and emission and meteorological factors during different periods, we found that the variability of local precipitation days (PDs), planetary boundary layer height (PBLH), near-surface wind speed (WS), and relatively humidity (RH) play different roles in influencing the haze pollution change during different historical periods. The joint effect of sharp increase of anthropogenic emissions, reduced PDs and WS intensified the haze pollution in SCB during 1980–1995. In contrast, decreased HDs during 1996–2005 are mainly attributable to the reduction of PM2.5 emission and the increase of PDs (especially in winter). In addition, the decrease of PDs is likely to be responsible for the unexpected increase in winter HDs over SCB in the last decade.

Effect of large topography on atmospheric environment in Sichuan Basin: A climate analysis based on changes in atmospheric visibility

“…Frontiers in Earth Science frontiersin.org severe in the basin in winter, followed by spring and autumn, and least severe in summer (Cai et al, 2018). Overall, on the basis of the preceding analysis, diffusion conditions for pollution are poor in the SCB under the particular large topography, and become progressively better with increasing altitude.…”

PM2.5 ∕ PM10 ratio prediction based on a long short-term memory neural network in Wuhan, China

“…where h (in meters) is the thickness of the mixing layer; U 10 (in meters per second) is the average wind velocity at a height of 10 m, which is 6 m s −1 ; a s and b s are the mixing layer coefficients; f is the ground rotation parameter; is the ground rotation angular velocity, with a value of 7.29×10 −5 rad s −1 ; and ϕ (in degrees) is the geographic latitude. The aerosol hygroscopic growth factor f (RH), where RH is the relative humidity, describes the extent to which the aerosol extinction cross section or scattering coefficient increases with increasing RH, depending on a variety of factors, such as the temperature absorption properties of the aerosol (Cai et al, 2018). The common formula for calculating f (RH) is…”

“…Although the relationship between the AOD and PM has been proven by many scholars, since the PM concentration level is usually measured at the surface, the correlation between them is affected by the planetary boundary layer height (PBLH) and relative humidity (RH) (Stirnberg et al, 2018;Chen et al, 2017). When studying the seasonal PM 10 -AOD correlation in northern Italy, Arvani et al (2016) found that the introduction of PBLH and RH correction can significantly improve the bin-averaged PM-AOD correlation.…”

Chinese blue days: a novel index and spatio-temporal variations

“…Haze pollution has been a fatal problem, affecting people's daily lives and causing serious economic losses (Ramanathan andRamana 2005, Gultepe et al 2007). As such, the variations in haze days have been studied intensively (Ding and Liu 2014, Chen and Wang 2015, Su et al 2015, Zhang et al 2015, Han et al 2016, Cai et al 2018.…”