1. What are the aerosol components responsible for haze?
a. How do the relative contributions of the aerosol components differ from
the best to typical to worst haze days?
b. How consistent are the relative and absolute aerosol component
contributions to haze from day to day, episodically, seasonally, from year
c. Are there geographic, land-use, elevation, or other site characteristics
that group sites with similar patterns of responsible components?
d. How do the relative contributions of aerosol components of haze compare
to relative emission rates of primary pollutants and precursor gases for
secondary pollutants near the site, in the sub-region and region?
2. What is the role of meteorology in the causes of haze?
a. What are the differences in meteorological conditions for best, typical,
and worst case haze days?
b. What are the empirical relationships between meteorological factors and
haziness and do they depend on time of year, the dominant aerosol
components, or other factors?
c. How well can best and worst haze days be predicted by meteorological
d. Are there geographic, land-use, elevation, or other site characteristics
that group sites with similar relationships between meteorology and
e. How well can the yearly variations in haziness be accounted for by
variations in meteorological conditions?
3. What are the emissions sources responsible for haze?
a. Are there geographic areas that when air is transported across on its way
to visibility protected FCIAs are often associated with best, typical and
worst case haze days?
b. What are the emission characteristics (from emissions inventories) within
transport areas associated with hazy conditions, and are they consistent
with the aerosol components responsible for the haziness?
c. What do aerosol characteristics on best, worst and typical days indicate
about emission sources (i.e. source types or specific sources)?
d. What can spatial and temporal pattern analyses indicate about the
locations and time periods associated with sources responsible for haze?
e. What connections can be made between highly sporadic emission sources
(e.g. dust storms & large forest fires) and haze conditions?
f. In light of the results addressing previous questions (a to e), what can
be inferred about the magnitude of impact from emissions outside of the
g. What refinements to the default natural visibility levels (Refer to
Guidance for Estimating Natural Visibility Conditions Under the Regional
Haze Rule) are justified for any FCIA or group of FCIAs based on ambient
monitoring and emissions data and the technical literature (i.e. without
doing air quality modeling)?
4. Are there any detectable and/or statistically significant multi-year
trends in the causes of haze?
a. Are the aerosol components responsible for haze changing?
b. For any detectable changes in aerosol components responsible for haze,
are the changes the results of meteorological changes and/or emissions
c. Where emissions are known to have changed substantially (based on
emission inventory data) is there corresponding change in haze levels?