84In particular, issues may arise when dealing with significant visibility contributions

from fires, coarse mass and fine soil (mostly wind-blown dust), and international transport (and

possibly other issues). Each of these issues should be addressed in the modeling protocol and

solutions should be discussed with the appropriate EPA Regional Office(s) on a case by case


7.0 How Can Additional Analyses Can Be Used to Support the

Attainment Demonstration?

By definition, models are simplistic approximations of complex phenomena. The

modeling analyses used to assess whether various emission reduction measures will bring an

individual area into attainment for the NAAQS contain many elements that are uncertain (e.g.,

emission projections, meteorological inputs, model response). These uncertain aspects of the

analyses can sometimes prevent definitive assessments of future attainment status. The

confidence in the accuracy of the quantitative results from a modeled attainment test should be a

function of the degree to which the uncertainties in the analysis were minimized. In general, by

following the recommendations contained within this guidance document, EPA expects that the

attainment demonstrations will mitigate the uncertainty as much as is possible given the current

state of modeling inputs, procedures, and science. However, while Eulerian air quality models

represent the best tools for integrating emissions and meteorological information with

atmospheric chemistry and no single additional analysis can match the expected reliability of

these models’ results, EPA believes that all attainment demonstrations will be strengthened by

additional analyses that can supplement the modeling analysis to enhance the assessment of

whether the planned emissions reductions will result in attainment.


n701 - n702 - n703 - n704 - n705 - n706 - n707 - n707 - n709 - n710 - n711 - n712 - n713 - n714 - n715 - n716 - n717 - n718 - n719 - n720 - n721 - n722 - n723 - n724 - n725 - n726 - n727 - n728 - n729 - n730 - n731 - n732 - n733 - n734 - n735 - n736 - n737 - n738 - n739 - n740 - n741 - n742 - n743 - n744 - n745 - n746 - n747 - n748 - n749 - n750


   Flag of Portugal 


 castellano: DISPER CUSTIC DESCAR RADIA    italiano:     


 français:    português:  






deutsch: DIS CUS  DES  RAD

castellano: DIS CUS DES  RAD   english: DIS CUS DES RAD  


 português: DIS CUS DES RAD   italiano:   DIS CUS  DES RAD


français:  DIS CUS DES RAD