Modeling analysis of the seasonal characteristics of haze formation in Beijing
Modeling analysis of the seasonal characteristics of haze formation in Beijing
复制标题
北京雾霾形成季节特征的模拟分析
DOI：
10.5194/acp-14-10231-2014
复制
发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Chai, F.
中科院分区：
文献类型：
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作者：
Han, X.;Zhang, M.;Chai, F.
应用区域大气模式系统RAMS-CMAQ(区域大气模式系统-社区多尺度空气质量)，结合气溶胶光学特性方案，模拟了2011年北中国平原的气象场、主要气溶胶组分(硫酸盐、硝酸盐、氨氮、黑碳、有机碳、沙尘和海盐)和地面能见度。选取2011年2月和7月的模拟结果进行分析，以深入了解北京不同季节的灰霾形成机制。模拟结果表明，北半球大部分地区的能见度都在10公里以下，在2、7月份的污染过程中，北京、天津、河北全省和山东西北部等特大城市的能见度降到了5公里以下。PM2.5的重质量浓度范围为120-300微克米(-3)，并集中在能见度较低的地区。北京冬季灰霾的形成机制与夏季不同。冬季PM2.5质量浓度较高，组分较复杂。虽然夏季PM2.5的质量浓度低于冬季，但吸湿性无机盐的质量浓度与冬季相当，相对湿度正如预期的那样更高。因此，吸湿气溶胶的吸水量在夏季起着关键作用。此外，分析表明，当PM2.5质量负荷大于100mgm(-3)时，其对能见度的影响很小。只有当PM2.5的质量负荷下降到一定的阈值区间时，能见度才会迅速增加。这表明，在采取减排措施控制灰霾发生的同时，PM2.5的质量负荷必须降至这一阈值区间以下。对北京市灰霾发生阈值与相对湿度之间的关系进行了指数函数拟合，拟合出的曲线可为理解和控制北京灰霾的形成提供新的理论依据。
The air quality modeling system RAMS-CMAQ (Regional Atmospheric Modeling System-Community Multiscale Air Quality), coupled with an aerosol optical property scheme, was applied to simulate the meteorological field, major aerosol components (sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt), and surface visibility over the North China Plain (NCP) in 2011. The modeled results in February and July 2011 were selected and analyzed to obtain an in-depth understanding of the haze formation mechanism in Beijing for different seasons. The simulation results showed that the visibility was below 10 km for most regions of the NCP, and dropped to less than 5 km over the megacities of Beijing and Tianjin, the whole of Hebei Province, and the northwest part of Shan-dong Province during pollution episodes in February and July. The heavy mass concentration of PM2.5 ranged from 120 to 300 mu g m(-3) and was concentrated in the areas with low visibility. The haze formation mechanism in Beijing in winter was different from that in summer. The mass concentration of PM2.5 was higher, and the components more complicated, in winter. While the mass concentration of PM2.5 in summer was lower than that in winter, the mass concentrations of hygroscopic inorganic salts were comparable with those in winter, and the relative humidity was, as expected, higher. Therefore, the water uptake of hygroscopic aerosols played a key role in summer. Moreover, the analysis showed that the influence of the PM2.5 mass burden on visibility was very weak when its value was larger than 100 mu g m(-3). Only when the mass burden of PM2.5 decreased to a certain threshold interval did the visibility increase rapidly. This indicates that, when emission reduction measures are taken to control haze occurrence, the mass burden of PM2.5 must be cut to below this threshold interval. The relationship between the threshold of haze occurrence and the relative humidity in Beijing was fitted by an exponential function, and the resulting fitting curves could provide a new theoretical basis to understand and control haze formation in Beijing.