For discussion FCR(95-96)69
on 3 November1995


Environmental Protection Department
New Subhead “Comprehensive air quality modelling system”

Members are invited to approve a commitment of $20 million for developing a comprehensive air quality modelling system.


The Environmental Protection Department (EPD) has no tools to carry out accurate territory-wide air quality impact assessments of major developments for the purpose of strategic planning and environmental policy formulation.


2. The Director of Environmental Protection (DEP) proposes to engage consultants to develop a comprehensive system of computer-assisted models capable of accurately predicting territory-wide air quality.


3. Deteriorating air quality poses hazards to human health. The major sources of air pollution in Hong Kong are motor vehicles, factories and power stations while construction activities also contribute a significant part. To limit the potential risks to the community, we need not only to tackle the present sources of air pollution, but also to ensure an adequate air quality impact assessment of development projects.

4. At present EPD operates a network of nine air quality monitoring stations within the urban area of Hong Kong to measure the air quality at specific locations. These monitoring stations however represent isolated point receptors. They only measure air quality at a specific location and at a specific time. They are unable to deal with the source of air pollution and the transport processes of air pollutants. As a result, they do not provide sufficient information to help project future air quality. In addition, we cannot assess the territory-wide air pollution level and the likely impact on air quality of major developments and pollution control measures based on the data of isolated locations. In view of the rapid urban growth in Hong Kong and neighbouring parts of China, we expect the current air quality situation to further deteriorate. It is therefore necessary to develop a tool capable of accounting for the sources, transport and transformation of air pollution in Hong Kong to allow planners to assess the air quality impact of different land use planning scenarios and policy changes with a view to arriving at the best option.

5. Due to Hong Kong’s complex topography, its proximity to the sea, and the configuration of its buildings, the assessment of air quality implications of major development proposals over the territory is very complicated. The air quality models presently available in the market can only cater for standard situations or individual local conditions and are not suitable for use in Hong Kong. We need to develop a comprehensive numerical air quality model specifically designed for Hong Kong to achieve the following objectives -

  1. to provide planners with accurate air quality projection for testing the environmental implication of landuse options at the strategic level; and
  2. to provide accurate air quality information to guide policy makers in formulating air management and control programmes.

6. Once available, the modelling system will be our standard assessment tool for strategic planning studies and formulation of environmental improvement measures. The system will take into account the complexity of Hong Kong’s topography, air flow and air pollutant emission and transformation patterns in a unified and comprehensive way.

7. The development of the system includes -

  1. establishing a system of numerical models to simulate the emission, dispersion and transformation of air pollution over Hong Kong;
  2. obtaining the necessary data and developing data-models to enable the execution and validation of the modelling system against measurements; and
  3. validating the modelling system and setting up the system on a host computer for air quality impact assessments in strategic planning and policy formulation.

8. DEP advises that the necessary resources for this work are currently not available within EPD and that it will not be cost-effective to carry out the work in-house within the required time-frame. He considers it necessary to engage consultants to develop the system.


9. DEP estimates that the consultants will take 18 months to develop the system at a non-recurrent cost of $20 million, broken down as follows -

$ million

(a) Establishing the modelling system


(b) Establishing an emission model and a geophysical database


(c) Analysis to construct a set of atmospheric data for a typical year


(d) Procuring the computer hardware for the model


(e) Conducting a validation study


(f) Miscellaneous expenses and contingencies




10. As regards 9(a), the estimated cost is for reviewing current meteorological and air quality situation in Hong Kong in order to determine the most suitable models for use, procuring, adapting, and developing the model for Hong Kong’s use, testing the models against measurements and running the models on a number of scenarios. It also includes $100,000 for computer software licence fees.

11. As regards 9(b), the estimated cost is for collecting and reviewing current available emission and geophysical data as well as comparing them with the emission models and geophysical database structures all over the world so as to set up an emission model and geophysical database most suitable for Hong Kong. The emission model will be used for making future projections.

12. As regards 9(c), the estimated cost is for analysing available data on the climatology of Hong Kong in relation to air pollution so as to construct a comprehensive picture of the air pollution climatology in Hong Kong and build up a set of atmospheric data of a typical year from different scenarios.

13. As regards 9(d), the estimated cost is for procuring a computer workstation of suitable configuration for housing the modelling system developed in the project.

14. As regards 9(e), the estimated cost is to cover materials, equipment, technical services, laboratory analysis and expenses for field studies for validating the system being developed. The database will be integrated into the modelling system.

15. As regards 9(f), the estimated cost covers fees and expenses incurred in providing training to EPD staff in the operation of the modelling system and setting up a panel of external advisors to ensure the technical integrity of the work, as well as a small amount for contingency.

16. The estimated cashflow is as follows -

$ million







Subject to Members’ approval of the proposal, we shall include sufficient provision in the annual Estimates for the purpose.

17. We estimate the recurrent cost of the proposal at $850,000 per annum. It will largely be required for operating and maintaining the system.


18. There is a need to assess environmental impacts of development programmes before embarking on an irreversible path of adopting a certain development strategy. This is even more pressing in rapid urban development. Major cities around the world have used comprehensive numerical air quality modelling systems to test and predict the effects of landuse planning and policy changes on air quality.

19. No other approach offers the same breadth of coverage, cost-effectiveness, non-intrusiveness and flexibility that a numerical modelling system can provide. We have to develop a tailor-made numerical modelling system for Hong Kong because of our unique geographical, meteorological and population-activity situations.

Planning, Environment and Lands Branch
October 1995

Last Updated on 2 December 1998