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  GEO-CAPE Science: Atmosphere

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. See Instrument Design Studies for more information.

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NASA Official: Doreen Neil
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