大气观测

2004年11月，由研究员J. William MUNGER和Chris P. NIELSEN (哈佛大学工程与应用科学学院) 以及郝吉明教授 (清华大学环境学院) 领衔，我们在北京以北的密云区设立了一座永久观测站，用来收集哈佛大学中国项目大气研究项目所需的独立数据。自投入使用以来，该观测站一直由清华大学方面主持运营，主要由哈佛大学中国项目的两位合作科学家：清华大学地球系统科学系的王聿绚教授和清华大学环境学院的王书肖教授负责。

密云观测站对几种主要痕量气体进行连续观测，包括一氧化碳、二氧化碳、臭氧、二氧化硫、一氧化氮／氮氧化合物，黑碳气溶胶和气象要素，同时即将新增对甲烷的观测。密云观测站坐落于北京以北100公里的郊区，远离其他污染源的干扰，从而可以准确测量出当地气象条件突变时，空气从相对干净到受到污染的过程中各种情况的变化。

研究团队已经将密云观测站观测到的数据同 GEOS-Chem模型结果进行了比较与整合，并且对臭氧、氮氧化合物，黑碳气溶胶、二氧化碳和一氧化碳比值，以及防控政策的效果进行了分析与评估。二氧化碳的详细数据已经中国碳循环研究详尽分析，并将发表在学术期刊和博士生Archana DAYALU的博士毕业论文中(由Bill MUNGER研究员和Steven C. WOFSY教授共同指导)。

哈佛大学中国项目的大气研究工作致力于就中国大气环境物理和化学两方面，从城市尺度到全球尺度，建立可通过观测验证的基础性研究框架。除了这里介绍的观测型研究方法以外，其他研究方法也包括建模研究(点击这里查看详情)以及自下而上的排放研究(点击这里查看详情)。

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声明：此处援引的部分论文出自美国国家科学基金会(NSF)ATM-1019134号或ATM-0635548号基金赞助项目(被引用论文中已注明)。这些论文中表达的任何观点、结论或建议均为作者本人观点，不代表美国国家科学基金会(NSF)的立场。

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Yu Zhao, Yutong Wang, Yiming Liu, Yueqi Jiang, Bo Zheng, Jia Xing, Yang Liu, Shuai Wang, and Chris Nielsen. 2023. “Sustained emission reductions have restrained the ozone pollution over China.” Nature Geoscience. Publisher's Version Abstract

Near-surface ozone pollution, associated with complex responses to changing precursor emissions and meteorological conditions, has become one of the biggest challenges in China’s air quality management. Here, we present the spatiotemporal evolution of ozone concentrations from 2010 to 2021 using measurements of the national air quality monitoring network. We evaluate the effectiveness of the national air pollution control programme, including Phase 1 (2013–2017) and Phase 2 (2018–2021), in reducing the ozone level over China, using an optimized machine learning approach, high-resolution emission estimates and an improved air quality model. We find that while emission changes in Phase 1 increased the ozone level over the five highly developed regions, further reductions of nitrogen oxide emissions in Phase 2 have generally constrained the ozone pollution. The changing effect of emission controls on ozone pollution is due to the shift in the prevailing regime for ozone formation and the weakened effects of aerosol declines, as emission reductions continue. We further find that current emission controls have been more effective in rural locales in four of the five regions, and more effective in summer than winter. Therefore, further control of ozone pollution should consider these regional and seasonal variations to identify the most important precursors for the pollution.

Xi Yang, Chris P. Nielsen, Shaojie Song, and Michael B. McElroy. 2022. “Breaking the “hard-to-abate” bottleneck in China’s path to carbon neutrality with clean hydrogen.” Nature Energy. Publisher's Version Abstract

Countries such as China are facing a bottleneck in their paths to carbon neutrality: abating emissions in heavy industries and heavy-duty transport. There are few in-depth studies of the prospective role for clean hydrogen in these ‘hard-to-abate’ (HTA) sectors. Here we carry out an integrated dynamic least-cost modelling analysis. Results show that, first, clean hydrogen can be both a major energy carrier and feedstock that can significantly reduce carbon emissions of heavy industry. It can also fuel up to 50% of China’s heavy-duty truck and bus fleets by 2060 and significant shares of shipping. Second, a realistic clean hydrogen scenario that reaches 65.7 Mt of production in 2060 could avoid US$1.72 trillion of new investment compared with a no-hydrogen scenario. This study provides evidence of the value of clean hydrogen in HTA sectors for China and countries facing similar challenges in reducing emissions to achieve net-zero goals.

Peter Sherman, Haiyang Lin, and Michael B. McElroy. 2022. “Projected global demand for air conditioning associated with extreme heat and implications for electricity grids in poorer countries.” Energy and Buildings. Publisher's Version Abstract

Human-induced climate change will increase surface temperatures globally over the next several decades. Climate models project that global mean surface temperature could increase by over 2˚C by 2050 relative to the preindustrial period, with even greater changes at the regional level. These temperature changes have clear and pertinent implications for extremes, and consequentially, heat-induced health issues for people living in particularly hot climates. Here, we study future projections in the demand for AC globally in the 2050s associated with extreme heat events. To do this, we employ an ensemble of CMIP6 models under high and low emissions scenarios. We find that the increasing frequency of extreme temperatures will cause a significant portion of the global population to be exposed to conditions that require cooling. This issue will be especially pervasive in poor countries such as India and Indonesia, which at present lack the AC units required to handle rapidly growing populations and increased frequencies of extreme temperatures. The electricity needed for cooling in these countries could reach as high as 75% of the current total annual electricity demand, which could place serious strain on the electricity grid infrastructure during peak cooling hours. We conclude that demand for cooling in the future will pose a significant challenge for poorer countries whose people will require AC units to handle extreme temperatures. In some countries, the grid infrastructure is insufficient at present to meet projected AC demands, and this need must be considered in future power systems planning.

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大气观测

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