Simplified ATMoS-4.0 Dispersion Model

A very important part of the air quality management process is looking at the contribution of various sources to pollution (commonly measured as mass over volume) – an entity different from emissions (commonly measured as mass over time). The process of converting emissions to concentrations is achieved through dispersion modeling. There are a number of dispersion modeling with varying degree of complexity, running at urban, regional, and global scales, to accommodate calculations at temporal scales of hours, days, months, seasons, and years. This step can be time consuming depending on the selected spatial and temporal scales, chemical mechanisms, and available computational capacity. In the SIM-air modeling system, the conversion of emissions to concentrations is simplified for a rapid assessment and is conducted in Excel, using a source-receptor transfer matrix (SRTM). The transfer matrix has to be established using a dispersion model, with local meteorology, for the select domain and then transferred to Excel, to enable further analysis to health impacts and optimization. The main advantage of doing this is that the dispersion model is run only once to generate SRTM and use the same for multiple scenario analysis. A note of caution – this is an approximation of full scale dispersion modeling runs and requires matrix validation before doing any further analysis. Also, this process is applicable for long term (yearly) analysis only and should be applied for episodal or short-term (like daily) analysis. ATMoS is our in-house dispersion modeling system used to generate SRTM for many urban and regional settings. The version 4.0 is now available as a simplified dispersion model using minimum data inputs and can be run on PCs and Linux machines (with proper environment setups).