Complex Interplay Between Organic and Secondary Inorganic Aerosols With Ambient Relative Humidity Implicates the Aerosol Liquid Water Content Over India During Wintertime
Complex Interplay Between Organic and Secondary Inorganic Aerosols With Ambient Relative Humidity Implicates the Aerosol Liquid Water Content Over India During Wintertime
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DOI：
10.1029/2021jd036430
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发表时间：
2022-07-16
影响因子：
4.4
通讯作者：
Gunthe, Sachin S.
中科院分区：
文献类型：
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作者：
Gopinath, Amar Krishna;Raj, Subha S.;Gunthe, Sachin S.
气溶胶液态水含量（ALWC）是大气气溶胶中普遍存在的成分，通过气溶胶表面反应调节大气化学，降低大气能见度。然而，在印度地区，ALWC对气溶胶化学和相对湿度（RH）的复杂依赖性仍然缺乏表征。在这里，我们将气溶胶化学成分的现有测量结果与热力学模型ISORROPIA2.1结合起来，揭示了印度大陆地区冬季细模气溶胶ALWC的全面情况。调节ALWC的因素主要依赖于相对湿度，因此在高相对湿度时，气溶胶干质量和吸湿性的影响显著，而吸湿性的影响随相对湿度的降低而显著降低。观察到ALWC显示出急剧的非线性上升，超过了取决于颗粒吸湿性的环境RH临界值。通过耦合Weather Research Forecasting-Chem simulation和ISORROPIA2.1进一步分析，发现印度上空ALWC的空间异质性显著，与气溶胶质量负荷和相对湿度高的区域密切相关。因此，印度恒河平原被观测到是一个高ALWC的热点，这解释了该地区冬季雾霾和烟雾的普遍情况。我们的研究结果再次强调，在有利的气象条件下，由强烈污染引起的高气溶胶质量对调节气溶胶-气候相互作用至关重要。观测结果表明，需要采取局部污染控制策略，旨在减少特定化学成分的气溶胶排放，这些化学成分通过该地区冬季ALWC的增加而导致PM的增强。
Aerosol Liquid Water Content (ALWC), a ubiquitous component of atmospheric aerosols, modulates atmospheric chemistry through aerosol surface reactions and reduces the atmospheric visibility. However, the complex dependency of ALWC on aerosol chemistry and relative humidity (RH) in the Indian region remains poorly characterized. Here, we combine available measurements of aerosol chemical composition with thermodynamic model, ISORROPIA2.1, to reveal a comprehensive picture of ALWC in fine mode aerosols during the winter season over the Indian continental region. The factors modulating ALWC are primarily dependent on the RH, such that the effect of aerosol dry mass and hygroscopicity are significant at high RH while the effect of hygroscopicity significantly reduces with decreasing RH. ALWC is observed to display a sharp non-linear rise, beyond a critical value of ambient RH dependent on the particle hygroscopicity. Further analysis by coupling Weather Research Forecasting-Chem simulation with ISORROPIA2.1 revealed significant spatial heterogeneity in ALWC over India, strongly associating with regions of high aerosol mass loading and RH. The Indo-Gangetic Plain is consequently observed to be a hotspot of higher ALWC, which explains the prevalent conditions of haze and smog during winter in this region. Our findings re-emphasize that high aerosol mass resulting from intense pollution is vital in modulating aerosol-climate interaction under favorable meteorological conditions. Observations suggest the need for localized pollution control strategies, directed at the reduction in aerosol emissions of specific chemical composition observed to contribute to the enhancement in PM through an increase in ALWC during wintertime in the region.