Outdoor air pollution has been a top global health concern for decades. However, questions like what causes the air pollution in cities, how the air pollution can affect public health, what we could do to improve the air quality forecast, and how the air quality would be like in the upper atmosphere, remain to be investigated. Motivated by these questions, my research has focused primarily on the atmospheric chemistry and the impacts of air pollutants (e.g., O3 and PM2.5) on public health and socio-economic characteristics of the population exposed. I've used a variety of model tools to investigate the chemical behaviors of air pollutants in the atmosphere and my research can be primarily branched out into the following aspects.

           My current research investigates detailed sources of the air pollutant—i.e., PM2.5, O3 and NO2—associated health impacts in various areas of the world using nested-grid capability the the chemical transport model GEOS-Chem and its adjoint.

• Europe: We've established a high-resolution (0.25°×0.3125°) adjoint calculation in Europe which allows us to examine the response of air pollution-related health impacts to a large number of sources. With remote sensing derived surface-level concentrations incorporated into, the adjoint sensitivity analyses are able to characterize km-scale spatial variability and the model biases can be further reduced. 

• China: We are working on the high-resolution adjoint calculation in China at the city level.

           To provide air quality forecast covering a longer time scale and a larger area in China, I participated in the establishment of the medium-range air quality forecast system as a principal member of the development team in Yangtze River Delta Center for Environmental Meteorology Prediction and Warning. The WRF-Chem based system has been providing 240-h air quality predictions every day over China since it was built in 2017. The forecast data is shared through the cloud platform of Shanghai Meteorological Service and the network of Chinese Meteorological Administration among cities every day.

           In our study of formation mechanism of air pollution in cities, we usually find that the urban canopy and local meteorological conditions are vital important in capturing the spatial and temporal variability of air pollutants, especially O3. In addition to affecting the accumulation, dispersion, and deposition of air pollutants, these factors affect chemical reactions in the atmosphere, which might greatly reduce the benefits brought by the emission reductions. By working with research team in SMS, IAP, and Nanjing University of Information Science & Technology, we investigated how the climate penalty and background concentration of O3 changed during the last decade, how the temperature-induced changes in isoprene emissions affect O3 concentrations,  how the oceanic air interacts with the urban O3 air quality, and how the regional transport affected the atmospheric composition and chemical behaviors of air pollutants during the pandemic, focusing on the city of Shanghai.

          Using the global chemical transport model GEOS-Chem and the Universal tropospheric-stratospheric Chemistry eXtension (UCX) mechanism, I worked with Professor Hong Liao in Chinese Academy of Sciences for my Ph. D. projects. We quantified the ignored nitrate contribution to summertime PM2.5 concentrations in the upper troposphere and lower stratosphere (UTLS) and the positive contribution of the chemical processes to summertime O3 concentrations in the UTLS over the Tibetan Plateau and South Asian Monsoon region.

          Beyond my model works, I also participated in several field observations, such as aerosol sampling in Guangzhou (Sun Yat-sen University), air quality monitoring in Dongtan, and the Shanghai Tower (SMS), and some lab work like measuring the composition of the volcanic ashes from the eruption of Mt. Pinatubo (Academia Sinica, Taiwan).