soundings (Chapter 2), sea surface temperature (Chapter 3), land cover (Chapter 4), aerosols (Chapter 7), and Earth's radiation budget (Chapter 9).

  • Diversity of satellite observations and sampling strategies and support for ground-based networks. An effective climate observing system depends on diverse satellite observations and sampling strategies, including measurements made by ground-based networks. The measurement tools must be responsive to the requirements imposed by the variables to be observed. While NPOESS and EOS have focused primarily on polar-orbiting satellites, satellite observations from other orbits (low inclination, geostationary) are also necessary (see Chapter 2, Chapter 3, Chapter 8, and Chapter 9). Some critical sensors will be flown by international partners, and so it will be important to integrate scientific findings on a more global basis (as discussed in Chapter 1, Chapter 3, Chapter 4, Chapter 5, Chapter 7 and Chapter 8).

    Surface- or ground-based networks to support process studies are also required, as discussed in Chapter 4, Chapter 5, and Chapter 7; concern for the neglect of these is expressed in Chapter 4. High-resolution measurements in both time and space (as discussed in Chapter 4, Chapter 5, Chapter 6, and Chapter 7) are a critical element of many process studies. As the observing systems improve, it is likely that undersampling (in time and space) will come to dominate the errors in the system (see Chapter 1, Chapter 2, Chapter 7, and Chapter 8). Innovative strategies, such as the use of satellite constellations, may be important for some applications, as expressed in Chapter 3.

  • Preserving the quality of data acquired in a series of measurements. It takes a special effort to preserve the quality of data acquired with different satellite systems and sensors, so that valid comparisons can be made over an entire set of observations. There are few examples of continuous data records based on satellite measurements where data quality is consistent across changes in sensors, even when copies of the sensor design are used. Sensor characterization and an effective, ongoing program of sensor calibration and validation are essential in order to separate the effects of changes in the Earth system from effects owing to changes in the observing system. Providing for overlap across successive sensors is critical, especially given the regular insertion of new technology driven by the need to reduce costs and/or improve performance. Concern about preventing data gaps, ensuring data continuity, and developing overlap strategies is expressed in Chapter 3, Chapter 4, Chapter 5, Chapter 7, Chapter 8, and Chapter 9. Data systems should be designed to meet the needs for periodic reprocessing of the entire data set. An aggressive, science-driven program to ensure long-term data quality and continuity is very important.

  • The role of data analysis and reprocessing. Improvements in understanding will come from continued, thorough analysis of new and ongoing observations. An active program of data analysis and reprocessing will add value to existing data sets by expanding the purposes for which they can be used and will enable development of new algorithms and new data products. Such analysis will also provide the basis for investment in new technologies for needed improvements such as innovative sensors.

  • Technology development and improved measurement capabilities. New sensors are needed to reduce costs and to improve measurement capabilities. For example, higher-resolution sensors could help resolve some of the still open questions discussed in Chapter 4, Chapter 5, and Chapter 7. Moreover, because all critical climate-related variables may not yet have been identified, and some, such as soil moisture (Chapter 6), cannot yet be measured effectively from space, continued technology and science investment is required. By coordinating its technology efforts with those of IPO/NPOESS, NASA could address these issues and help provide increased capabilities for the operational meteorological system.

Status of NASA and IPO/NPOESS Integration
  • Division of responsibility in the integration of research and operational missions. Climate research and monitoring raise issues that transcend the capabilities of any single federal agency. There is currently no effective structure in place in the federal government that can address such multiagency issues as the balance between satellite and ground observations, long-term and exploratory missions, and research and operational needs. The committee concurs with the several recent NRC reports that have expressed concern over the lack of overall authority and accountability, the division of responsibility, and the lack of progress in achieving a long-term climate observing system (see, for example, NRC 1998a,b and 1999a,b; see also footnote 3 in Chapter 1). The challenges in integration of NASA/ESE research satellite missions and IPO/NPOESS operational satellite missions highlight the critical issues.

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