Guidelines on the Use of Alternative Computer Models in Air Quality Assessment

Guidelines on the Use of Alternative Computer Models in Air Quality Assessment

1. Background

1.1 In Hong Kong, a three tier assessment approach to air quality assessment is adopted (refer to the “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts” for the definition of the different tiers). Different kinds of air quality models are employed to suit the purpose of each tier. These frequently used models (as listed in Schedule 1 of ‘Guidelines on Choice of Models and Model Parameters’; hereafter referred to as Schedule 1 models) form the basic set of modeling tools for local-scale air quality assessment in Hong Kong.

1.2 However, no single model is sufficient to cover all situations encountered in regulatory applications. To ensure that the best model available is used for each regulatory application and that a model is not arbitrarily applied, the project proponent (and/or its environmental consultants) should assess the capabilities of various models available and adopt one that is most suitable for the project concerned.

1.3 Examples of situations where the use of an alternative model is warranted include:

(i) the complexity of the situation to be modelled far exceeds the capability of the Schedule 1 models; and
(ii) the performance of an alternative model is comparable or better than the Schedule 1 models.

1.4 This paper outlines the demonstration / submission required in order to support the use of an alternative air quality model for regulatory applications for Hong Kong.

2. Required Demonstration / Submission

2.1 Any model that is proposed for air quality applications and not listed amongst the Schedule 1 models will be considered by EPD on a case-by-case basis. In such cases, the proponent will have to provide the followings for EPD's review:

(i) Technical details of the proposed model; and
(ii) Performance evaluation of the proposed model.

Based on the above information, EPD will determine the acceptability of the proposed model for a specific or general applications. The onus of providing adequate supporting materials rests entirely with the proponent.

2.2 To provide technical details of the proposed model, the proponent should submit documents containing at least the following information:

(i) mathematical formulation and data requirements of the model;
(ii) any previous performance evaluation of the model; and
(iii) a complete set of model input and output file(s) in commonly used electronic format.

2.3 EPD may have already acquired information on a proposed alternative model. To avoid wastage, the proponent should first check with EPD to determine if the supporting documents for the alternative model is already accessible to EPD and hence do not need to be submitted.

2.4 EPD reserves the right to require from the proponent of an alternative model any further information on the model for technical review.

Modelling Section, Air Science and Modelling Group
Environmental Protection Department
January 2023


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