Project No: 16202120

Title: Assessment of decadal NO2 variations over the Greater Bay Area in Southern China

Principal Investigator: Prof. Alexis LAU

Co-Investigator: Dr. Changqing LIN


Rapid economic development and urbanization in the Guangdong-Hong Kong-Macau Greater Bay Area (GBA) have caused major air pollution issues, including severe nitrogen dioxide (NO2) pollution. Nitrogen dioxides are an essential precursor in the formation of tropospheric ozone, acid rain and nitrate particles, and they significantly exert adverse impacts on human health. However, research on NO2 pollution is less than that on particulate matter pollution. Enhanced ground-based monitoring of NO2 concentration has been available since only 2013. Knowledge about the long-term spatiotemporal variation, causes, and environmental impacts of NO2 pollution is far from complete because of the lack of long-term measurements. The proposed study will develop an integrated approach by using a variety of advanced methods to investigate the decadal NO2 pollution in this region. These methods include but are not limited to polar-orbiting and newly developed geostationary satellite remote sensing, chemical transport model (CTM), drone-based sensor measurement, and ground-based LIDAR and radiosonde measurements. Satellite remote sensing technique measures the vertical column density of NO2 with an extensive spatial and temporal coverage. Recent developments in geostationary satellites offer new opportunities to observe the atmosphere with a high resolution of 1 hour. The emission-based CTM is capable of demonstrating three-dimensional NO2 pollution variation and the tracking the emission sources. Given the model’s uncertainty in simulating NO2 variation, a systematic evaluation is needed. Most previous model’s evaluations relied on ground measurements only. Observations of the NO2 vertical variation are still limited. This study uses the newly developed drone-based system equipped with miniaturized NO2 sensor to measure the NO2 vertical profile across the GBA for the model’s evaluation and improvement. The LIDAR and radiosonde measurements provide critical information on the planetary boundary layer height, which determines the convection and dispersion of NO2 pollution. In summary, the proposed study will take advantage of a variety of advanced measurements and modeling techniques to deduce and investigate the decadal NO2 pollution variation; to better understand the vertical variation of NO2 and its impact on surface NO2 pollution; to improve the chemical transport model’s ability in simulating the NO2 variation; and to investigate the effects of different emission sources and meteorological factors on the decadal NO2 pollution variation. We envision that enhanced understanding about long-term NO2 pollution can provide scientific evidence for the development of appropriate strategies for NO2 pollution control and serve the green development objective of the GBA.