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Atmosphere

Science Studies

Air quality measurements are urgently needed to understand the complex consequences of increasing
anthropogenic pollutant emissions both regionally and globally. The current observation system for
air quality is inadequate to monitor population exposure and develop effective emission-control strategies.
The scales of variability of the processes leading to poor air quality require continuous,
high-spatial-resolution and high-temporal-resolution measurements possible only from geosynchronous Earth orbit.

GEO-CAPE’s Atmospheric Science Questions explore the influence of both gases and particles on air quality, atmospheric composition, and climate.

  1. What are the temporal and spatial variations of emissions of gases and aerosols that are important for air quality and climate?
  2. How do physical, chemical, and dynamical processes determine tropospheric composition and air quality over scales ranging from urban to continental, diurnally to seasonally?
  3. How does air pollution drive climate forcing and how does climate change affect air quality on a continental scale?
  4. How can observations from space improve air quality forecasts and assessments for societal benefit?
  5. How does intercontinental transport affect surface air quality?
  6. How do episodic events, such as wild fires, dust outbreaks, and volcanic eruptions, affect atmospheric composition and air quality?

These Science Questions guided the development of the Atmosphere Science Traceability Matrix [PDF],

and many Planning Studies have guided the evolution of the measurement requirements.

east coast view positioned satellite map image with capitol map zone out
In the planned configuration, atmospheric observations will be made from a geostationary orbit positioned near 100 W to
regularly view the domain extending from 10 N to 60 N and from the Pacific to the Atlantic Oceans.
Land and near-coastline regions will be sampled hourly; open ocean regions will be sampled daily.
The horizontal product resolution will be approximately 4 km x 4 km in the center of the domain, nominally 100 W and 35 N.
A higher spatial resolution cloud camera will be included to avoid cloud contamination in the retrieved products.

GEO-CAPE will provide measurements hourly for solar zenith angles < 70°, with 4 km x 4 km product horizontal spatial resolution at the center of the domain. Gases to be measured include: ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), formaldehyde (HCHO), methane (CH4), ammonia (NH3), and glyoxal (CHOCHO). Two pieces of information are desired in the troposphere with sensitivity to the lowest 2 km for O3 and CO to allow separation of the lower-most troposphere from the free troposphere. Aerosol properties of Optical Depth (AOD), Absorption Optical Depth (AAOD), Optical Centroid Height (AOCH) and Aerosol Index (AI) will also be measured.

Ozone is important in many aspects of atmospheric chemistry; thus, accurate measurements of O3 with
as much vertical resolution as possible in the troposphere are desirable. Vertical information can be
obtained from multi-spectral observations that rely on different physical processes in the atmosphere.

image of MISR instrument
Multi-spectral observations of tropospheric pollutants have been demonstrated for the ozone precursor
and outstanding atmospheric tracer, CO, by combining information from the CO spectral bands at 4.6
micrometers and 2.3 um. The combined information enables estimates of near-surface CO
concentrations and of CO above the boundary layer. Near-surface concentrations are essential to
characterize pollution sources. CO in the free troposphere is a tracer of transported pollution.
Together, these observations allow differentiation between local pollution
production and pollution transported from one location to
another. Finally, by obtaining the multi-spectral information at
each location throughout the day, GEO-CAPE identifies
vertical pollution transport, out of the boundary layer and into
the free troposphere. GEO-CAPE will use multispectral
approaches to provide daytime information on CO and O3.

Air quality measurements are urgently needed to understand the complex consequences of increasing
anthropogenic pollutant emissions both regionally and globally. The current observation system for
air quality is inadequate to monitor population exposure and develop effective emission-control strategies.
The scales of variability of the processes leading to poor air quality require continuous,
high-spatial-resolution and high-temporal-resolution measurements possible only from geosynchronous Earth orbit.

GEO-CAPE’s Atmospheric Science Questions explore the influence of both gases and particles on air quality, atmospheric composition, and climate.

  1. What are the temporal and spatial variations of emissions of gases and aerosols that are important for air quality and climate?
  2. How do physical, chemical, and dynamical processes determine tropospheric composition and air quality over scales ranging from urban to continental, diurnally to seasonally?
  3. How does air pollution drive climate forcing and how does climate change affect air quality on a continental scale?
  4. How can observations from space improve air quality forecasts and assessments for societal benefit?
  5. How does intercontinental transport affect surface air quality?
  6. How do episodic events, such as wild fires, dust outbreaks, and volcanic eruptions, affect atmospheric composition and air quality?

These Science Questions guided the development of the Atmosphere Science Traceability Matrix [PDF],

and many planning studies have guided the evolution of the measurement requirements.

east coast view positioned satellite map image with capitol map zone out
In the planned configuration, atmospheric observations will be made from a geostationary orbit positioned near 100 W to
regularly view the domain extending from 10 N to 60 N and from the Pacific to the Atlantic Oceans.
Land and near-coastline regions will be sampled hourly; open ocean regions will be sampled daily.
The horizontal product resolution will be approximately 4 km x 4 km in the center of the domain, nominally 100 W and 35 N.
A higher spatial resolution cloud camera will be included to avoid cloud contamination in the retrieved products.

GEO-CAPE will provide measurements hourly for solar zenith angles < 70°, with 4 km x 4 km product horizontal spatial resolution at the center of the domain. Gases to be measured include: ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), formaldehyde (HCHO), methane (CH4), ammonia (NH3), and glyoxal (CHOCHO). Two pieces of information are desired in the troposphere with sensitivity to the lowest 2 km for O3 and CO to allow separation of the lower-most troposphere from the free troposphere. Aerosol properties of Optical Depth (AOD), Absorption Optical Depth (AAOD), Optical Centroid Height (AOCH) and Aerosol Index (AI) will also be measured.

Instrument Design

Ongoing studies continue to refine GEO-CAPE measurement and instrument requirements.
Specific instruments for GEO-CAPE have not yet been selected. At this preliminary stage,
several concepts are being studied to ensure that a range of potential instruments can
meet GEO-CAPE requirements.

The Science Traceability Matrix [PDF]
shows the species to be measured by GEO-CAPE, the scientific objectives to which they respond,
and the corresponding measurement requirements. Ozone, aerosols, and an ensemble of precursors
are included to better understand the related sources, transport, chemistry, and climate forcing.
Methane is included because of its importance as a greenhouse gas. CO and O3 retrievals include
two pieces of information in the troposphere, including sensitivity below 2 km, in order to discriminate
near-surface pollution and to better characterize pollutant transport.
The measureĀ¬ment of aerosol optical depth (AOD) is complemented by aerosol absorption optical depth (AAOD),
aerosol index (AI), and height [aerosol optical centroid height (AOCH)]. A higher spatial resolution cloud
camera will be included to avoid cloud contamination in the retrieved products.

The attainment of a trace-gas quantity in the lowermost troposphere (LMT)
will be achieved through a multispectral approach to provide daytime information on CO and potentially ozone.
In addition to the ultraviolet (UV), ozone also has absorption features in the visible (VIS)
and thermal infrared (TIR) ranges that can provide information on its vertical distribution within the troposphere.
Because of its importance in so many aspects of atmospheric chemistry, an accurate measurement of O3 with as much
vertical resolution as possible in the troposphere is desirable. The ability to retrieve concentrations
in the LMT is important for the characterization of pollution sources, and when combined with a free troposphere profile,
also allows local production to be discriminated from transported pollution.

Several instrument concepts have been advanced which could meet the needs of GEO-CAPE Atmospheric Science,
ranging from a single instrument with a wide spectral range [PDF]
to combinations of complementary instruments which encompass the suite [PPT] of necessary measurements.
Many of these designs [PPT] have been supported by the Earth Science Technology Office.

Related Programs and Field Studies

DISCOVER-AQ, or Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality.

EPA AirNOW, daily AQI (air quality index) forecasts as well as real-time AQI conditions
for over 300 cities across the U.S., and links to more detailed State and local air quality websites.

TOLNet, Tropospheric Ozone Lidar Network, ground-based profiling of tropospheric ozone.

https://geo-cape.larc.nasa.gov/atmosphere/?preview=true

MPLNET, Micro-Pulse Lidar Network, a federated network of Micro-Pulse Lidar systems
to measure aerosol and cloud vertical structure continuously, day and night,
over long time periods for climate change studies and ground validation for satellites.

AERONET, AErosol RObotic NETwork, ground-based remote sensing aerosol network federation that provides a long-term,
continuous and readily accessible public domain database of aerosol optical, microphysical and radiative.

PANDORA: link and info TBD.

Related Programs and Field Studies: Ocean

Application Areas

The atmospheric component of GEO-CAPE will advance the monitoring, assessment, and forecasting
of air quality in the US. Primary partner agencies include the US EPA and NOAA because of their
roles in air quality monitoring and forecasting. Many of these applications of GEO-CAPE-type
data were discussed at a coordinated EPA-NASA workshop, as summarized in a presentation at the GEO-CAPE 2011 Community Workshop [PPTX].

All of the “science” questions posed in the GEO-CAPE Science Traceability Matrix [PDF]
are also fundamental “applications” questions. The NASA Air Quality Applied Sciences Team is prototyping many
of these applications. GEO-CAPE will provide information to the air quality community at spatial and temporal scales relevant for analysis of high-emission
corridors within urban areas, the photochemical cycles involving nonmethane hydrocarbons, nitrogen oxides (NOx), and O3, and the variability induced by
mesoscale meteorological phenomena (e.g., land/sea breezes).

Application Areas: Ocean