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Atmospheric Composition

Atmospheric composition determines air quality and affects weather, climate, and critical constituents such as ozone. Exchanges with the atmosphere link terrestrial and oceanic pools within the carbon cycle and other biogeochemical cycles. Solar radiation affects atmospheric chemistry and is thus a critical factor in atmospheric composition. The ability of the atmosphere to integrate surface emissions globally on time scales from weeks to years couples several environmental issues including global ozone depletion and recovery and its impact on surface ultraviolet radiation, climate forcing by radiatively active gases and aerosols, and global air quality. Thus, atmospheric chemistry and associated composition are a central aspect of Earth system dynamics.

The research strategy for furthering our understanding of atmospheric composition is geared to providing an improved prognostic capability for the recovery of stratospheric ozone and its impacts on surface ultraviolet radiation, the evolution of greenhouse gases and their impacts on climate, and the evolution of tropospheric ozone and aerosols and their impacts on climate and air quality. Toward this end, research within the atmospheric composition focus area addresses the following science questions:

  • How is atmospheric composition changing?
  • What trends in atmospheric constituents and solar radiation are driving global climate?
  • How do atmospheric trace constituents respond to and affect global environmental change?
  • What are the effects of global atmospheric chemical and climate changes on regional air quality?
  • How will future changes in atmospheric composition affect ozone, climate, and global air quality?

NASA expects to provide: the necessary monitoring and evaluation tools to assess the effects of climate change on ozone recovery and future atmospheric composition; improved climate forecasts based on our understanding of the forcings of global environmental change; and air quality forecasts that take into account the feedbacks between regional air quality and global climate change.

Research seeks to develop quantitative understanding of:

  • Changes in atmospheric composition and the timescales over which they occur,
  • Forcings (anthropogenic and natural) that drive the changes,
  • Response of atmospheric trace constituents to global environmental change and the subsequent effects on global climate, and
  • Effects of global atmospheric chemical and climate changes on regional air quality.

Atmospheric Composition Roadmap
Chart: As depicted on the above roadmap, achievements in these areas via advances in observations, data assimilation, and modeling enable improved predictive capabilities for describing how future changes in atmospheric composition affect ozone, climate, and air quality. [+ larger image]

Drawing on global observations from space, augmented by suborbital and ground-based measurements, NASA is uniquely poised to address these issues. This integrated observational strategy is furthered via studies of atmospheric processes using unique sub-orbital platform-sensor combinations to investigate, for example: (1) the processes responsible for the emission, uptake, transport, and chemical transformation of ozone and precursor molecules associated with its production in the troposphere and its destruction in the stratosphere; and (2) the formation, properties, and transport of aerosols in the Earth's troposphere and stratosphere. The research strategy in the atmospheric composition focus area encompasses an end-to-end approach for instrument design, data collection, analysis, interpretation, and prognostic studies.

Through the implementation of a robust program of research over the past two decades, we have made significant progress in our current level of understanding of the variability of, forcings on, responses to, and consequences of changes in atmospheric composition. However, many questions remain. For example, halogen chemistry is known to be largely responsible for stratospheric O3 loss, but the roles of chemistry vs. dynamics remain to be precisely quantified. The connection between climate change and ozone chemistry has been recognized, but uncertainties remain regarding the effects on the timing and extent of ozone recovery. In the troposphere, we have observed varying trends in ozone; however its geographical evolution and trends remain to be quantified. Similarly, the spatial and temporal variations in the oxidizing capacity require further characterization. Global observations have shown transport of tropospheric ozone over large (hemispheric) distances. However, the extent to which regional pollution can be attributed to such long-range transport remains to be quantified. In the climate area, radiatively important changes in atmospheric water vapor have been observed, but these temporal variations are not quantitatively understood so that future changes can be predicted. Observational advances have yielded important information on the geographical and vertical distribution of atmospheric aerosols. Nevertheless significant further study is required before we can fully quantify aerosol evolution, composition, vertical distribution, and radiative impacts at a level where the information can be used in climate models.