tailieunhanh - Air Quality Part 9

Tham khảo tài liệu 'air quality part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Estimation of uncertainty in predicting ground level concentrations from direct source releases in an urban area using the USEPA s AERMOD model equations 193 For the condition of ambient temperature in CBL the contribution of variance by vertical dispersion parameter and wind speed increased with downwind distance and decreased for all other parameters for both the surface roughness lengths considered. Similar pattern can be observed in SBL for the condition of lower ambient temperature with the exception that wind speed showed an opposite trend to that observed in CBL. However for the case of higher ambient temperature in SBL the contribution to variance increases for horizontal distribution and emission rate and decreases for vertical dispersion parameter and wind speed with increase in downwind distance. For both high and low values of ambient temperature the contribution by wind speed was significant in SBL compared to CBL. Thus one can state that the concentrations are more sensitive to higher temperatures and wind speed in SBL than in CBL. The sensitiveness in Monin-Obukhov length condition showed similar behavior to that of wind speed condition. It was observed that emission rate had more contribution to variance than vertical dispersion parameter in SBL for the cases having lower values of Monin-Obukhov length wind speed and ambient temperature. The remaining parameters defined in the assumption cells have negligible contribution to variance when compared to vertical dispersion parameter and total horizontal distribution function. 4. Conclusions The objective of the study was to perform uncertainty and sensitivity analyses in predicting the concentrations from the AERMOD equations. As it is difficult to perform uncertainty and sensitivity analyses using the original AERMOD model an approximate set of AERMOD equations were programmed in Excel. The predicted concentrations from the AERMODCBL and AERMODSBL models were compared to the predicted concentrations .

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