Space and Atmospheric Sciences division, Physical Research Laboratory, Ahmedabad, India.
EWRE Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India.
Sci Rep. 2020 Apr 3;10(1):5862. doi: 10.1038/s41598-020-62710-8.
Fine particulate matter (PM, aerodynamic diameter ≤2.5 µm) impacts the climate, reduces visibility and severely influences human health. The Indo-Gangetic Plain (IGP), home to about one-seventh of the world's total population and a hotspot of aerosol loading, observes strong enhancements in the PM concentrations towards winter. We performed high-resolution (12 km × 12 km) atmospheric chemical transport modeling (WRF-Chem) for the post-monsoon to winter transition to unravel the underlying dynamics and influences of regional emissions over the region. Model, capturing the observed variations to an extent, reveals that the spatial distribution of PM having patches of enhanced concentrations (≥100 µgm) during post-monsoon, evolves dramatically into a widespread enhancement across the IGP region during winter. A sensitivity simulation, supported by satellite observations of fires, shows that biomass-burning emissions over the northwest IGP play a crucial role during post-monsoon. Whereas, in contrast, towards winter, a large-scale decline in the air temperature, significantly shallower atmospheric boundary layer, and weaker winds lead to stagnant conditions (ventilation coefficient lower by a factor of ~4) thereby confining the anthropogenic influences closer to the surface. Such changes in the controlling processes from post-monsoon to winter transition profoundly affect the composition of the fine aerosols over the IGP region. The study highlights the need to critically consider the distinct meteorological processes of west-to-east IGP and changes in dominant sources from post-monsoon to winter in the formulation of future pollution mitigation policies.
细颗粒物（PM，空气动力学直径≤2.5μm）对气候有影响，降低能见度，并严重影响人类健康。印度-恒河平原（IGP）是世界总人口的七分之一的家园，也是气溶胶负荷的热点地区，在冬季观测到 PM 浓度强烈增加。我们进行了高分辨率（12km×12km）大气化学输送建模（WRF-Chem），以揭示该地区冬季向冬季过渡期间的潜在动力学和区域排放的影响。该模型在一定程度上捕捉到了观测到的变化，揭示了 PM 的空间分布在后季风期间具有增强浓度（≥100μg/m）的斑块，在冬季期间演变为整个 IGP 地区的广泛增强。卫星观测火灾的敏感性模拟表明，IGP 西北部的生物质燃烧排放在后季风期间起着至关重要的作用。然而，相反，在冬季，大气温度的大幅下降、更浅的大气边界层和较弱的风导致停滞状态（通风系数降低约 4 倍），从而将人为影响限制在更接近地面的范围内。从后季风到冬季的过渡过程中控制过程的这些变化深刻地影响了 IGP 地区的细气溶胶组成。该研究强调需要在制定未来污染缓解政策时，认真考虑从西到东的 IGP 不同的气象过程和从后季风到冬季主要来源的变化。
