Re ECF Project: 2008-12

Project Title: The Impacts of South China Monsoon Climate Variability and El Niño on Hong Kong Air Quality

Applicant: The City University of Hong Kong (Dr. Wen ZHOU)

Total Approved Grant: $249,880

Duration: 16/4/2009 to 15/4/2011

Project Status/Remarks: Completed

To study the relationships between climate conditions and air quality in Hong Kong. The differential and synergistic effects of summer/winter monsoon climate, and the El Nino/La Nina will be investigated for their impacts on Hong Kong air quality. An air quality warning system will also be developed based on the relationship between air pollution index (API) and South China Monsoon circulations.

Summary of the Findings/Outcomes:
The research provides a science-based knowledge of variations in air quality in a changing climate. Air quality of Hong Kong appears to be significantly influenced by the South China Monsoon and ENSO. The key results are described in the following:

  1. The cross correlation was conducted to indentify the relationship between the ENSO and different air pollutants. The analysis indicates that a negative sign in the correlation coefficient was found when the ENSO leads air pollutant concentrations by 2 months.
  2. For each season except summer, the lower quartile of the visibility shows positive trends that have potential implications for the endangerment of human health in Hong Kong. It is also important to note that a quantile-based trend assessment provides a relatively complete change in distribution and asymmetric trends for various quantile. However, other approaches are not suitable to indentify trends, especially in cases where changes in tail distribution are evident, while no significant changes are observed in other quantiles.
  3. During the El Niño years, changes in the visibility show the opposite signal between summer and autumn. In El Niño summer, a relatively better visibility is shown, while autumn time visibility is diminished in the decaying year of El Niño events. However, there are no significant changes in the visibility for the La Nina years.
  4. The rank analysis indicates that lower air quality levels occurred during both the strong SCS summer monsoon and strong EAWM season. In addition, relatively lower air quality days are more likely to have occurred in the post-2005 period than the pre-2005 period.
  5. Based on the conditional API risk assessment, specific vulnerabilities were diagnosed. During the strong SCS summer monsoon, it was found that a1.5- to 2-fold increase in the API risk. However, the impact of the EAWM on the API risk is less clear.
We believe that this research provides useful information for the station-specific air quality management and developing the air quality warning systems.