In 2018 summer, Professor Amos Pui-kuen TAI and his research team established an Ozone Garden to analyse the ozone impact of ground level ozone on vegetation in Hong Kong.
Hong Kong is a metropolitan city with a population of around 8 million people in a land area of ~1000 km2. However, more than 75% of the land area is classified as countryside with forests and farmland. Hong Kong has a sub-tropical climate and because of its mountainous terrain, it has a high biodiversity with some species that are endemic to Hong Kong. With urbanisation in south China and increased industrial activities, air pollution is becoming a serious problem in Hong Kong. Ozone pollution threatens human health and also ecosystems. For plants, ozone induces early leaf death and can negatively impact growth in both natural vegetation and crops. We therefore propose to establish a free-air experimental garden to monitor, quantify and understand the mechanisms of ozone damage on plants.
During this experiment, dubbed the “ozone garden”, we will grow cultivars of beans with different ozone sensitivities, which will act as bio-indicators of the local air pollution impacts on ecosystems. Such a free-air ozone garden has been built at multiple locations in the US and Europe, but will be the first of its kind in South China. The data obtained from this garden will be essential to not only demonstrate the impacts of air pollution on plants under locally specific environmental conditions, but can also be used to derive important parameters of ecophysiology and biometeorology that can be used to build a regionally relevant earth system model for predictive purposes.
To set up this ozone garden, we have found a small plot of land in the Chinese University of Hong Kong. This land was also used for growing soybeans and rice for research purposes. The next thing we did is to purchase an ozone analyzer. There are a lot of ozone monitors on the market but they are usually not sensitive enough. After some serious searching, we found a laboratory graded ozone analyzer Teledyne 400 ozone analyzer. It is cited in many high profile research papers, because it provides a very accurate measurement that is up to 0.01ppb precision. This amazing instrument also comes with a very expensive price tag, which we were fortunate to get funding for.
The T400 uses a UV analyzer to compare the sampled air and the scrubbed clean air to get the ozone concentration. To make sure it works in optimal conditions, we need to ensure that the humidity and temperature is controlled and limited to around 25-30 degree Celsius. In Hong Kong, summer temperatures can often be higher than 30 degrees C. As we don’t have funding to build an air conditioned room for it, we used a simple solution. We put the ozone analyzer inside a plastic box with styrofoam insulation and installed fans and a Peltier cooler to cool it down. After some days of engineering and design, we successfully managed to keep the box temperature under 30 degrees even when it was 36 degrees outside. We placed it under a shed and started recording the ozone.
Professor Amos Pui-kuen TAI (second right), Dr. Felix Pui-kin LEUNG (first left) and other research team members visited the experimental site for investigating ozone and plant interaction at the Institute of Atmospheric Physics, Chinese Academy of Science in Beijing in May 2018.
The research findings of Professor Steve Hung-lam YIM and his research team improved the knowledge of cloud-aerosol-turbulence interactions and also transboundary air pollution under the influence of extreme weather events. The new understanding supports weather and air quality forecasts more precise and representative.
This project developed the 3DREAMS in Hong Kong, which is the first-of-its-kind in Asia, to reveal the complicated, stochastic, and no-linear atmospheric boundary layer (ABL) processes in an urban environment. The Hong Kong Environmental Protection Department will develop a monitoring system similar to 3DREAMS. The CUHK team was awarded a consultancy project to conduct a measurement using 3DREAMS and hence provide professional references for the government proposed measurement plan. Our CUHK team PI, Prof. Steve Yim, was recently invited to be an individual expert on the World Health Organization (WHO) Global Air Pollution and Health – Technical Advisory Group (GAPH-TAG). Our collaboration with local government and the international organization shows the significant impact of our research.
Here provides more specific descriptions of our findings.
Firstly, upper-level wind measurements were conducted to explore the turbulent mixing in cloud-topped boundary layer. It assessed the contribution of cloud radiative cooling and determined the altitudinal dependence of the contribution of surface heating and vertical wind shear on turbulent mixing. The characteristics of the vertical distribution of cloud- and surface- driven turbulence in the sub-cloud layer was explored, improving the understanding of the ABL dynamics. This study has been published in Remote Sensing (IF: 4.5) (Huang et al., 2020).
In addition, our team identified three types of surface air pollution with five episodes during the typhoon Danas (16/7-19/7, 2019). The study found the important role of TAP in the increases in surface PM and O3 concentrations with significant vertical wind shear that transported pollutants to the ground level. Similar vertical aerosol distributions and wind profiles suggest the comparable TAP contributions at the two sites and thus infer the critical role of local O3 photochemical process in the O3 difference. This study provides evidence that during TAP induced by typhoon, vertical wind shear is a critical process for vertical transport of the upper level transboundary air pollution to the ground level. This study has been published in Environmental Pollution (IF: 6.8) (Huang et al., 2021).
Next, to comprehensively understand the aerosol-turbulence interaction in transboundary air pollution (TAP), a year-long intensive observation of upper-level wind and aerosol at multiple sites in Hong Kong was conducted using 3DREAMS. This study shows the heterogeneity of the ABL induced by orographic topography. The interactions between advected aerosol and local accumulated aerosol via different sizes of eddies was also revealed. This study emphasizes the spatial variation and diurnal variation of the ABL processes, and has been published in Geophysical Research Letters (IF: 4.6) (Huang et al., 2021).
Publications:
Huang, T., Yim, S. H. L., Yang, Y., Lee, O. S. M., Lam, D. H. Y., Cheng, J. C. H., & Guo, J. (2020). Observation of turbulent mixing characteristics in the typical daytime cloud-topped boundary layer over Hong Kong in 2019. Remote Sensing, 12(9), 1533.
https://doi.org/10.3390/rs12091533
Huang, T., Li, Y., Cheng, J. C., Haywood, J., Hon, K. K., Lam, D. H., ... & Yim, S. H. L. (2021). Assessing Transboundary‐local Aerosols Interaction over Complex Terrain Using a Doppler LiDAR Network. Geophysical Research Letters, e2021GL093238.
https://doi.org/10.1029/2021GL093238
Huang, T., Yang, Y., O’Connor, E. J., Lolli, S., Haywood, J., Osborne, M., ... & Yim, S. H. L. (2021). Influence of a weak typhoon on the vertical distribution of air pollution in Hong Kong: A perspective from a Doppler LiDAR network. Environmental Pollution, 276, 116534. https://doi.org/10.1016/j.envpol.2021.116534 Impact Factor: 8.071 (2020)
Professor Gabriel Ngar-cheung LAU, Emeritus Professor of Department of Geography and Resource Management (GRM), and Senior Advisor, former Director cum Programme Leader (Climate and Environmental Changes) of the Institute of Environment, Energy and Sustainability (IEES) at The Chinese University of Hong Kong (CUHK), has been elected as a recipient of 2020 Class of American Geophysical Union (AGU) Fellow. Since 1962, AGU has elected fewer than 0.1% of members to join this prestigious group of individuals.
Professor Gabriel Ngau-cheung LAU is a world-renowned climate scientist who specializes in in the diagnosis of atmospheric circulation system, large-scale air-sea interaction and regional phenomena related to climate change. He is also a contributing author of Nobel Peace Prize-winning Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), and a lead author of Fifth Assessment Report (AR5) which contributed to the Paris Agreement.
Citation
Professor Lau is honored for his innovative diagnoses leading to important advances in understanding of atmospheric low-frequency variability and El Niño teleconnection dynamics.
References :
Randall, D. A., Wood, R. A., Bony, S., Colman, R., Fichefet, T., Fyfe, J., ... & Taylor, K. E. (2007). Cilmate Models and Their Evaluation. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (FAR) (pp. 589-662). Cambridge University Press. https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch8.html
Christensen, J. H., Krishna Kumar, K., Aldrian, E., An, S. I., Cavalcanti, I. F. A., de Castro, M., Dong, W., Goswami, P., Hall, A., Kanyanga, J. K., Kitoh, A., Kossin, J., Lau, N. C., Renwick, J., Stephenson, D. B., Xie, S. P. & Zhou, T. (2013). Climate Phenomena and their Relevance for Future Regional Climate Change. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 1217-1308). xCambridge University Press. https://www.ipcc.ch/report/ar5/wg1/climate-phenomena-and-their-relevance-for-future-regional-climate-change/
About AGU Fellows program
AGU Fellows program recognizes members who have attained scientific eminence in the Earth and space sciences for achieving a breakthrough, discovery, or innovation in their field. The scientific breakthroughs and the paradigm shift that AGU Fellows have led is recognized and admired by their peers in the Earth and space sciences community, as well as by the general public.
Professor Gabriel Ngar-cheung LAU (top right hand corner, circled in grey) was recognized in the AGU 2020 Honors & Recognition Ceremony during the AGU Fall Meeting.
