previously ignored sustainability issues and provide governments with the information necessary
to do so. It must be borne in mind, however, that
there are many pitfalls in the design of consolidated metrics [134], and only a correctly designed
metric will lead to sound decision making.
A standardized set of data for use with widely
accepted consolidated metrics would clarify the
design goals of monitoring campaigns, which is
important to the cost-efficiency of monitoring
[14]. Information derived would be more similar
from campaign to campaign, allowing monitoring
groups to more easily share data. Further development of consolidated metrics in the direction of
sustainability and the design of monitoring efforts
to serve this development would allow the air
pollution monitoring community to come to a
consensus on the types of data to be counted in
the metrics and the weighting of these data.
Development of Satellite Observations Satellite
observations can be used in combination with
models and in situ measurements to reduce statistical uncertainty in estimates [83]. Recent work by
van Donkelaar et al. [90] has made possible the
reliable estimation of long-term average PM 2.5 concentration based on satellite-derived data. Aerosol
Optical Depth (AOD) measurements made by the
MODIS (Moderate Resolution Imaging Spectroradiometer) and MISR (Multiangle Imaging Spectrometer) instruments on the Terra satellite were
combined with estimates of aerosol distribution
from the Goddard Earth Observing System chemical transport model (GEOS-chem). Previously, variations in meteorology, aerosol composition, and
distribution have prevented accurate estimates by
satellite observation beyond small regions, but
with the GEOS-Chem model, reliable estimates
were obtained across all midlatitude areas of the
globe. The concentration estimates with 10 km
2
spatial resolution were obtained.
Many epidemiological studies of PM 2.5 exposure are limited by a dearth of monitoring data,
and the improved satellite estimates from the van
Donkelaar et al. 2010 work [90], can now provide
some of these needed data [90]. The lack of data is
more pronounced in developing countries, and
these countries often have pronounced PM 2 . 5
management problems, making these estimates
particularly useful. van Donkelaar et al. [90] also
suggest that increased satellite coverage could
further improve the identification of temporal or
spatiotemporal trends. In contrast, other recent
attempts to estimate PM 2.5 concentrations using
satellite-observed AOD with fine spatial resolution determined that AOD is a poor tool for
assessing spatial PM2.5 patterns [135],
supporting previous suggestions that current satellite spatial resolution is not sufficient for the
intra-urban scale [82]. AOD was also found to
contribute little additional information when
incorporated into a predictive model that was
already accounting for land use, emissions
sources, meteorology, and regional variability
[135]. Thus, the most effective role of satellite
data is still being established, but this tool has
the potential to become a valuable and routine
part of air pollution monitoring, providing data
where there otherwise may be few and improving
data where routine rigorous monitoring is taking
place.
Martin [82] reviews the many recent improvements in the application of satellite observations
to assessments of air quality but includes a number of limitations in obtaining accurate pollutant
concentrations. Limitations included the need for
more ground-level NO 2 measurement to validate
satellite-observed NO 2 data and difficulty in
obtaining high-quality O 3 concentration estimates. Martin’s work asserts that in terms of
instrumentation, air quality monitoring via the
current satellites is at a peak but that substantial
progress could be made with a new generation of
instruments, with more satellites in a variety of
orbits (as opposed to all satellites being in sunsynchronous orbit as is currently the case). Specific instrument improvements include a minimization of pixel size, which will reduce the number
of pixels obscured by clouds. Work that can be
accomplished without additional satellites and a
new generation of instrumentation includes the
improvement of models critical to the interpretation of satellite observations. Better estimations
from these models will improve information
derived [82]. If the suggested developments can
be made, satellite observations will move closer to
Air Pollution Monitoring and Sustainability
415
to do so. It must be borne in mind, however, that
there are many pitfalls in the design of consolidated metrics [134], and only a correctly designed
metric will lead to sound decision making.
A standardized set of data for use with widely
accepted consolidated metrics would clarify the
design goals of monitoring campaigns, which is
important to the cost-efficiency of monitoring
[14]. Information derived would be more similar
from campaign to campaign, allowing monitoring
groups to more easily share data. Further development of consolidated metrics in the direction of
sustainability and the design of monitoring efforts
to serve this development would allow the air
pollution monitoring community to come to a
consensus on the types of data to be counted in
the metrics and the weighting of these data.
Development of Satellite Observations Satellite
observations can be used in combination with
models and in situ measurements to reduce statistical uncertainty in estimates [83]. Recent work by
van Donkelaar et al. [90] has made possible the
reliable estimation of long-term average PM 2.5 concentration based on satellite-derived data. Aerosol
Optical Depth (AOD) measurements made by the
MODIS (Moderate Resolution Imaging Spectroradiometer) and MISR (Multiangle Imaging Spectrometer) instruments on the Terra satellite were
combined with estimates of aerosol distribution
from the Goddard Earth Observing System chemical transport model (GEOS-chem). Previously, variations in meteorology, aerosol composition, and
distribution have prevented accurate estimates by
satellite observation beyond small regions, but
with the GEOS-Chem model, reliable estimates
were obtained across all midlatitude areas of the
globe. The concentration estimates with 10 km
2
spatial resolution were obtained.
Many epidemiological studies of PM 2.5 exposure are limited by a dearth of monitoring data,
and the improved satellite estimates from the van
Donkelaar et al. 2010 work [90], can now provide
some of these needed data [90]. The lack of data is
more pronounced in developing countries, and
these countries often have pronounced PM 2 . 5
management problems, making these estimates
particularly useful. van Donkelaar et al. [90] also
suggest that increased satellite coverage could
further improve the identification of temporal or
spatiotemporal trends. In contrast, other recent
attempts to estimate PM 2.5 concentrations using
satellite-observed AOD with fine spatial resolution determined that AOD is a poor tool for
assessing spatial PM2.5 patterns [135],
supporting previous suggestions that current satellite spatial resolution is not sufficient for the
intra-urban scale [82]. AOD was also found to
contribute little additional information when
incorporated into a predictive model that was
already accounting for land use, emissions
sources, meteorology, and regional variability
[135]. Thus, the most effective role of satellite
data is still being established, but this tool has
the potential to become a valuable and routine
part of air pollution monitoring, providing data
where there otherwise may be few and improving
data where routine rigorous monitoring is taking
place.
Martin [82] reviews the many recent improvements in the application of satellite observations
to assessments of air quality but includes a number of limitations in obtaining accurate pollutant
concentrations. Limitations included the need for
more ground-level NO 2 measurement to validate
satellite-observed NO 2 data and difficulty in
obtaining high-quality O 3 concentration estimates. Martin’s work asserts that in terms of
instrumentation, air quality monitoring via the
current satellites is at a peak but that substantial
progress could be made with a new generation of
instruments, with more satellites in a variety of
orbits (as opposed to all satellites being in sunsynchronous orbit as is currently the case). Specific instrument improvements include a minimization of pixel size, which will reduce the number
of pixels obscured by clouds. Work that can be
accomplished without additional satellites and a
new generation of instrumentation includes the
improvement of models critical to the interpretation of satellite observations. Better estimations
from these models will improve information
derived [82]. If the suggested developments can
be made, satellite observations will move closer to
Air Pollution Monitoring and Sustainability
415