Response of winter fine particulate matter concentrations to emission and meteorology changes in North China

Abstract

The winter haze is a growing problem in North China, but the causes are not well understood. The chemistry version of the Weather Research and Forecasting model (WRF-Chem) was applied in North China to examine how PM 2.5 concentrations change in response to changes in emissions (sulfur dioxide (SO 2 ), black carbon (BC), organic carbon (OC), ammonia (NH 3 ), and nitrogen oxides (NO x )), as well as meteorology (temperature, relative humidity (RH), and wind speeds) changes in winter. From 1960 to 2010, the dramatic changes in emissions lead to +260 % increases in sulfate, +320 % increases in nitrate, +300 % increases in ammonium, +160 % increases in BC, and +50 % increases in OC. The responses of PM 2.5 to individual emission species indicate that the simultaneous increases in SO 2 , NH 3 , and NO x emissions dominated the increases in PM 2.5 concentrations. PM 2.5 shows more notable increases in response to changes in SO 2 and NH 3 as compared to increases in response to changes in NO x emissions. In addition, OC also accounts for a large fraction in PM 2.5 changes. These results provide some implications for haze pollution control. The responses of PM 2.5 concentrations to temperature increases are dominated by changes in wind fields and mixing heights. PM 2.5 shows relatively smaller changes in response to temperature increases and RH decreases compared to changes in response to changes in wind speed and aerosol feedbacks. From 1960 to 2010, aerosol feedbacks have been significantly enhanced due to higher aerosol loadings. The discussions in this study indicate that dramatic changes in emissions are the main cause of increasing haze events in North China, and long-term trends in atmospheric circulations may be another important cause since PM 2.5 is shown to be substantially affected by wind speed and aerosol feedbacks. More studies are necessary to get a better understanding of the aerosol-circulation interactions.

Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain

“…For SO 4 2− , the change is the lowest compared with those of the other two inorganic aerosols, with the relative differences lower than 5%. In spite of the different simulations with that reported in Gao et al (), our results multiplied by 5 times (considering the linearity response to the NH 3 emission) are consistent with those reported as 189.6, 84, and 5.3% for NO 3 − , NH 4 + , and SO 4 2− , respectively. The total response of PM 2.5 to the NH 3 changes (Figure ) is in the range of 25 to 55% (5–11% per 20% NH 3 increase) over the NCP.…”

“…The poor agreements during some periods may be due to the uncertainties in the meteorological simulations. Different from that reported in Gao et al (2016), the uniform relative increase in NH 3 emission for each grid is chosen in this study for examining the sensitivity of formation of inorganic aerosols to the NH 3 perturbation. The clean period, which is defined as the concentration of PM 2.5 lower than 75μg/m 3 , has been chosen instead of the nonpolluted days for comparison with the polluted case in a super-ideal manner.…”

China's Clean Air Action has suppressed unfavorable influences of climate on wintertime PM<sub>2.5</sub> concentrations in Beijing since 2002

“…The Fast-j radiation scheme (Wild et al, 2000) was selected to calculate photolysis rates. These 135 configurations have been shown in previous studies (Gao et al, 2016a(Gao et al, , 2016b to be capable of reproducing winter haze episodes in North China.…”

Hybrid Mass Balance/4D‐Var Joint Inversion of NOx and SO2 Emissions in East Asia

“…Quantification of long-term NO x and SO 2 emission are important for evaluation of air quality regulations (e.g., de Foy et al, 2016). Their emissions are also used in chemical transport models to study the formation of PM 2.5 (e.g., Tao et al, 2017;Zhang et al, 2015) and causes of haze (e.g., Gao et al, 2016;Zhang et al, 2016).…”