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Integrating Research and Operational Missions in Support of Climate Research

That Earth's climate has changed and that it will continue to do so is well appreciated. Nevertheless, there are persistent questions regarding present climate trends on a decadal or centenary time scale and the appropriate policies for responding to climate change. Within this framework, there is the need both to determine the processes controlling climate change and variability and to monitor climate change.

There is occasionally the perception that process studies require observing systems that are different from systems for monitoring. This is not always the case, especially with regard to studies involving climate variability. For example, study of the processes underlying the El Niño/Southern Oscillation (ENSO) requires a variety of data types comprising consistent observations over many years. Thus, the requirements for process studies and monitoring tend to merge as the time scale of the phenomena of interest increases.

Both operational and research satellite systems have played an important role in the development of our understanding of Earth processes (NRC, 1995). Although the primary focus of the operational systems is on short-term weather prediction and the protection of life and property, they have also played a vital role in study of the Earth. The operational nature of these systems has ensured that the data record is nearly complete, spanning more than 30 years in certain cases. Many of the variables important for weather forecasting are also critical for understanding climate-related processes as well as climate monitoring. Sea surface temperature (SST) is a notable example of such a parameter. It is frequently used as a diagnostic variable in global circulation models, as well as input in short-term weather forecasts. It is also used in commercial applications, such as identifying prime fishing areas. In contrast, research observing systems are relatively short-lived (less than 5 years) and focus on a specific scientific or technical issue. However, there are many examples where research missions survive for long time periods or involve repeated flights of the same research sensor. For example, copies of the Total Ozone Mapping Sensor (TOMS) have been flown for nearly 20 years, providing a valuable record of long-term changes in stratospheric ozone.

Monitoring climate change has stringent requirements. Depending on the time scale of interest and the nature of the particular process, the signal may be small relative to other sources of variability. For example, it has been projected that global SST will increase 0.25 °C per decade in response to increasing atmospheric concentrations of CO2. However, ENSO events will dominate SST variability on interannual time scales. This implies that the SST record will have to be compiled over many years and with high precision and accuracy to detect this projected response.



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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN 1 Integrating Research and Operational Missions in Support of Climate Research That Earth's climate has changed and that it will continue to do so is well appreciated. Nevertheless, there are persistent questions regarding present climate trends on a decadal or centenary time scale and the appropriate policies for responding to climate change. Within this framework, there is the need both to determine the processes controlling climate change and variability and to monitor climate change. There is occasionally the perception that process studies require observing systems that are different from systems for monitoring. This is not always the case, especially with regard to studies involving climate variability. For example, study of the processes underlying the El Niño/Southern Oscillation (ENSO) requires a variety of data types comprising consistent observations over many years. Thus, the requirements for process studies and monitoring tend to merge as the time scale of the phenomena of interest increases. Both operational and research satellite systems have played an important role in the development of our understanding of Earth processes (NRC, 1995). Although the primary focus of the operational systems is on short-term weather prediction and the protection of life and property, they have also played a vital role in study of the Earth. The operational nature of these systems has ensured that the data record is nearly complete, spanning more than 30 years in certain cases. Many of the variables important for weather forecasting are also critical for understanding climate-related processes as well as climate monitoring. Sea surface temperature (SST) is a notable example of such a parameter. It is frequently used as a diagnostic variable in global circulation models, as well as input in short-term weather forecasts. It is also used in commercial applications, such as identifying prime fishing areas. In contrast, research observing systems are relatively short-lived (less than 5 years) and focus on a specific scientific or technical issue. However, there are many examples where research missions survive for long time periods or involve repeated flights of the same research sensor. For example, copies of the Total Ozone Mapping Sensor (TOMS) have been flown for nearly 20 years, providing a valuable record of long-term changes in stratospheric ozone. Monitoring climate change has stringent requirements. Depending on the time scale of interest and the nature of the particular process, the signal may be small relative to other sources of variability. For example, it has been projected that global SST will increase 0.25 °C per decade in response to increasing atmospheric concentrations of CO2. However, ENSO events will dominate SST variability on interannual time scales. This implies that the SST record will have to be compiled over many years and with high precision and accuracy to detect this projected response.

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN WEATHER AND CLIMATE The requirements for a program of climate research are often perceived to be in conflict with what is required for weather services: climate-related studies require long-term consistency whereas weather services (e.g., forecasts, severe weather warnings) require rapid delivery of data products. However, climate can be viewed as the long-term statistics of weather. This linkage may be exploited to meet both sets of requirements. Thus variables that are critical for weather forecasting, such as atmospheric profiles of temperature and humidity, are also important for climate research and modeling. One of the fundamental differences is the time scale over which both the forecasts and the observations must be made. For example, simple weather forecasts based on persistence (i.e., tomorrow's weather will be the same as today's) work well over short time scales. On longer time scales, more complicated models and a richer observation suite are required. For example, ocean processes (such as ocean circulation) and terrestrial processes (such as evapotranspiration) need to be included to produce forecasts with sufficient capability or to understand the critical processes. It is possible to generalize by noting that as the time scale of interest increases, more processes and more complicated interactions become important. This effect leads to the occasional surprises noted in the overview of the Pathways report (NRC, 1998a)—the unexpected processes or linkages that appear in studies of climate change. Box 1.1 elaborates further on the distinctions between weather and climate. Nonlinear processes and the increasing number of interacting processes make it impossible to define a priori all of the types and scales of observations that need to be made. Accordingly, there should be balance between the focused research missions where the scientific underpinnings are well known and the wide-open, broadly based observations of some operational missions. The Pathways report overview (NRC, 1998a) discusses a scientific framework to support an observing strategy. This framework builds on the first decade of the U.S. Global Change Research Program (USGCRP) and identifies several areas of science and observations where a renewed focus and a rebalancing of priorities are required. A noteworthy inference that can be drawn from the Pathways report is that establishing a robust understanding of the linkages between large-scale global processes and smaller-scale regional processes is an enormous challenge. For example, changes in ecosystem structure may be linked to changes in the patterns of climate variability, which in turn have feedbacks on the climate system. Moreover, public policy will respond to such regional-scale impacts rather than to broad-scale global change in mean Earth system properties. The Earth Observing System (EOS) and National Polar-orbiting Operational Environmental Satellite System (NPOESS) missions need to accommodate this scientific framework and balance the often conflicting primary missions of operational and research systems, the needs for continuity and innovation, and the needs for process studies and long-term monitoring. LONG-TERM MEASUREMENTS The characteristic scales of climate variability demand long time series in order to determine the critical processes as well as to separate natural variability from anthropogenic influences. Unlike weather forecasting, the interval between stimulus and response can be several years to centuries. With a high level of background variability, subtle changes in Earth's climate system can be difficult to detect. This problem is further complicated by the changes in instrument technology or sampling strategies that may occur during the period of observations. The task of assembling a record of total solar irradiance (Willson and Hudson, 1991) illustrates the challenges facing the development of long-term consistent time series. Developing this record required a rigorous calibration and sensor characterization program and an observation approach that ensured sufficient temporal overlap (as well as sensor validation) to achieve accurate cross-calibration between successive sensors. Another notable example is the record of upper-troposphere temperature (NRC, 2000). In the science community, long-term data sets are sometimes perceived as being the result of unchanging data collection activities that are not at the forefront of innovative research. It is difficult to base a scientific career on such an activity. Nevertheless, the atmospheric CO2 record started by C.D. Keeling at Mauna Loa shows the importance of such long-term records and how the scientific value of such time series increases as the record

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Box 1.1 Distinguishing Weather and Climate “Weather,” the current condition of the atmosphere, is usually described in terms of temperature, cloud cover, wind, and precipitation. Operational weather forecasts attempt to predict the evolution of these variables over the next few hours or days at specific locations to answer questions such as, Will it rain today or tomorrow? or Am I threatened by severe weather? “Climate” research focuses on long time scales and addresses questions such as, How does today's weather compare with that of a decade, a century, or a millennium ago? Are there long-term trends in regional and global variables? If so, why? Will there be another Ice Age or human-induced global warming? The signal of these types of fluctuations can be extremely small compared with daily weather changes. For example, the “climate” variation of globally averaged decadal temperatures over the past 500 years has been only about 1 °C. It is not uncommon, however, to observe day-to-day variations in local “weather” that produce temperature changes of many times that amount. Weather forecasting and climate research, therefore, place different demands on data and consequently necessitate different strategies for making and utilizing observations. The key factors distinguishing the strategies are time scale and precision. Operational weather observations require near-real-time access to data for rapid processing so that the current state of the atmosphere can be adequately characterized in terms of physical variables in order that computer models may provide timely projections. The interval from taking an observation to processing it is often less than 1 hour. Climate researchers, though, have the luxury of time to sift through the observations (if the data have been archived and are accessible) in order to assess their precision and utility. Virtually all observations needed for operational weather forecasts, if properly calibrated, are valuable for climate research, but several climate-sensitive parameters have little bearing on the weather forecast for the next week or so. Such variables as ocean topography and salinity, ice-cap thickness, volcanic activity, stratospheric temperatures, atmospheric chemical composition, and ground cover, for example, are generally treated as constants for the operational forecast period. However, small variations in these components are critical for understanding longer-term climate issues. Monitoring climate variables requires a permanent commitment to systematic observations, some of which have little immediate value for the task of weather forecasting. In addition, because operational weather forecasting is generally the mission of a national or multinational institution, conventional observations (e.g., of rainfall or surface temperature) tend to be clustered in the forecast area and often are not made systematically across institutions. Climate fluctuations occur on a global scale, and characterizing them requires uniformly distributed and systematically observed data collected without regard for national boundaries or human schedules. length increases (Keeling et al., 1996). Moreover, the Mauna Loa record also is an excellent case study of the programmatic difficulty in maintaining such time series. The level of personal and political commitment needs to be high, and short-term funding strategies and traditional peer review often work in opposition. Thus the science community often considers such long time series to be the purview of the operational agencies where long-term funding can be sustained. There may be negative consequences to such a strategy. First, it may separate data collection from active research, so that the process degrades to passive monitoring. Second, operational agencies sometimes have constrained budget flexibility, and with good reason they are reluctant to assume a continuing mandate for data collection without sufficient resources. The more that long-term time series are entitlements in an agency budget, the less flexibility an agency may have to pursue new activities.

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN NASA'S APPROACH TO LONG-TERM OBSERVATIONS The original plans for EOS included three nearly identical groups of satellites, with each group lasting 5 years. The resulting 15-year data set would form the basis for climate research and modeling. Implicitly, it was assumed that a subset of these observations and their associated requirements would find their way into the operational observing systems and continue indefinitely. In some cases, such a research/operational partnership was developed explicitly; for example, the afternoon platform, PM-1, was assumed to be of particular interest for both operational weather and climate research applications. The Atmospheric Infrared Sounder (AIRS) was one example of a NASA sensor that was expected to find a home in the NOAA POES. As the plans for EOS shifted in response to changing budget and scientific pressures, the idea of repeated flights of similar platforms and sensors was dropped. Instead, NASA focused on continuity of 24 key measurements (Table 1.1), which could perhaps be achieved by a variety of sensors during the 15-year EOS program. NASA proposed that the original EOS measurements could be divided into two categories: process measurements that would last only for a limited time period and monitoring measurements that would need to be maintained throughout the life of the EOS program. The process for dividing the EOS observation set into these two categories was begun in 1995, but it was never brought to fruition. In briefings to the committee, NASA officials described a new process for defining the second series of EOS missions. The Earth science community will propose science-driven mission concepts. NASA officials expressed their intention to base mission design more directly on science questions than may have been the case previously. The missions would begin operation in 2004, 5 years after the launch of the first EOS platform, Terra (formerly known as AM-1). It is expected that the new missions will be considerably cheaper than the first series. TABLE 1.1 The 24 Measurements Planned for EOS Discipline Measurement Atmosphere Cloud properties Radiative energy fluxes Precipitation Tropospheric chemistry Stratospheric chemistry Aerosol properties Atmospheric temperature Atmospheric humidity Lightning Land Land cover and land use change Vegetation dynamics Surface temperature Fire occurrence Volcanic effects Surface wetness Ocean Surface temperature Phytoplankton and dissolved organic matter Surface wind fields Ocean surface topography Cryosphere Land ice change Sea ice Snow cover Solar Radiation Total solar irradiance Ultraviolet spectral irradiance

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Current NASA plans include continuation of a subset of what NASA has designated “systematic measurements” as well as a transition of other measurements to operational programs such as NPOESS. A key component of this strategy is the NPOESS Preparatory Project (NPP), which is tentatively scheduled for launch in 2006. The NPP will carry a subset of the NPOESS sensors (the Visible/Infrared Imager and Radiometer Suite (VIIRS), Conical Scanning Microwave Imager/Sounder (CMIS), Advanced Technology Microwave Sounder (ATMS), and Cross-Track IR Sounder (CrIS)); NASA has been working with the IPO to improve these sensors to meet some of the EOS science requirements (e.g., to incorporate some of the MODIS capabilities for visible imaging in VIIRS). Continuity of other missions (such as high-resolution land imaging) in the post-EOS era is more problematic. NASA has moved from its rigid plan of flight copies of EOS hardware to a program that is much more flexible and in some sense less predictable. Unlike the days of the Operational Satellite Improvement Program in which NASA flight-tested hardware for the National Oceanic and Atmospheric Administration (NOAA) weather satellites (NRC, 1995), there is no structured program in NASA to develop sensors for use in NPOESS. This does not mean that such transfers cannot happen; a conscious effort on the part of the two programs could facilitate such collaboration. In fact, NASA has stated that it will not develop any sensors for the operational agencies unless there is a clear commitment to continued flight of such a sensor after its initial demonstration. NOAA'S APPROACH TO LONG-TERM OBSERVATIONS The 1994 Presidential Decision Directive directing the Department of Defense and the Department of Commerce to develop a converged Defense Meteorological Satellite Program/Polar-orbiting Operational Environmental Satellites program1 initiated a process to identify joint agency requirements for the combined system. This process involved operational and research users, both internal and external to the two programs. Not surprisingly, agreement on joint agency requirements was difficult as the DMSP and POES programs serve distinct user communities. Eventually, the agencies codified their agreement on the requirements for NPOESS in the Integrated Operational Requirements Document (IORD-1; IPO NPOESS, 1996). The IORD-1 consists of 61 environmental data records (EDRs) that were deemed necessary to the success of NPOESS (see Table 1.2). Of these, 6 were defined by the DOD as mission-critical. Unlike the more flexible research requirements that characterize NASA missions, the EDR process relied on a well-defined set of measurements that had demonstrable value for the primary mission of NPOESS. For example, weather forecasting models are relatively mature, and it is fairly straightforward to quantify the improvements in model predictive skill given the availability of a particular data set. The user community for NPOESS data is well defined, and specific EDRs were often developed to meet their application needs. On the other hand, climate modeling is far more complex and less advanced, so it is difficult to quantify the effects on predictive skill. Observations for climate research tend to be broad in scope, with the expectation that new insights will be gained based on the availability of long-term, well-calibrated data. Moreover, it is unrealistic to expect that climate science requirements can be met simply through a better definition of measurement requirements for NPOESS. Climate research involves far too many processes at a wide range of time and space scales. For each EDR, both a “threshold” and an “objective” were defined by the IPO. The threshold refers to the minimum set of standards that must be met for the measurement to be a success. The objective refers to the desired standards. For many climate change applications, instrument stability is a key standard, yet it is undefined for many of the EDRs. Typically, each EDR defines measurement quality and sampling characteristics without specifying the measurement technology. In March 1996, NOAA sponsored a workshop that brought together a broad panel of climate research scientists to evaluate the applicability of the NPOESS EDRs for climate studies (NOAA, 1997). In general, the NPOESS measurements meet some climate research requirements in terms of accuracy. However, many climate research objectives require that NPOESS sensors meet the EDR objective requirements, not simply the EDR threshold. In addition, many research requirements depend on the details of the technical implementation, which are not captured in the EDR. For example, measuring sea surface topography requires precise knowledge of satellite orbit and tides, which are not discussed in the IORD. Once a contractor and design have been selected, important information on the proposed instrument characteristics and associated product algorithms will become available to the climate research community for evaluation and peer review. However, unless a flexible contract is negotiated that will allow changes to be made to the design and the algorithms, considerable costs could be incurred by accommodating the climate community needs. 1   “Fact Sheet: U.S. Polar-Orbiting Operational Environmental Satellite Systems and Convergence of U.S. Polar-Orbiting Operational Environmental Satellite Systems and Landsat Remote Sensing Strategy,” statement by the White House Press Secretary, May 10, 1994. Available on the World Wide Web at <http://www.whitehouse.gov/WH/EOP/OSTP/NSTC/html/pdd2.html>.

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN TABLE 1.2 Environmental Data Records for NPOESS Discipline Measurement Key parameters (essential baseline measurements that must be provided by NPOESS) Atmospheric vertical moisture profiles Atmospheric vertical temperature profiles Imagery Sea surface temperature Sea surface winds Soil moisture Atmospheric parameters Aerosol optical thickness Aerosol particle size Ozone total column/profile Precipitable water Precipitation (type and rate) Pressure (surface and profile) Suspended matter Total water content Cloud parameters Cloud base height Cloud cover and layers Cloud effective particle size Cloud ice water path Cloud liquid water Cloud optical depth and transmittance Cloud top height Cloud top pressure Cloud top temperature Earth radiation budget parameters Surface albedo Downward longwave radiation at the surface Insolation Net shortwave radiation at the top of the atmosphere Solar radiance Total longwave radiation at the top of the atmosphere Land parameters Land surface temperature Normalized difference vegetation index Snow cover and depth Vegetation and surface type Ocean and water parameters Currents Freshwater ice motion Ice surface temperature Littoral sediment transport Net heat flux Ocean color and chlorophyll Ocean wave characteristics Sea ice age and motion Sea surface height and topography Surface wind stress Turbidity

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Space environmental parameters Auroral boundary Auroral energy deposition Auroral imagery Electric field Electron density profiles and ionospheric specification Geomagnetic field In situ ion drift velocity In situ plasma density In situ plasma fluctuations In situ plasma temperature Ionospheric scintillation Neutral density profile/neutral atmosphere Radiation belt and low energy solar particles Solar and galactic cosmic ray particles Solar extreme ultraviolet flux Supra-thermal through auroral energy Upper atmospheric airglow The IPO has specified stability requirements for many variables in the IORD-1. These variables include cloud effective particle size, cloud-top pressure, cloud-ice-water path, cloud optical depth, cloud-top height, cloud-top temperature, total column ozone and ozone profile, aerosol particle size, aerosol optical thickness, albedo, and normalized difference vegetation index (NDVI). Although these stability requirements are not complete and have not been reviewed by the climate research community to ensure their adequacy, they do represent an important shift in the direction of operational satellite systems. The IORD-1 refers to NOAA's “climate monitoring mission” and notes that the U.S. government requirements include “seasonal and interannual climate forecasts; . . . decadal-scale monitoring of climate variability; . . . [and] assessment of long-term global environmental change” as part of NPOESS (IPO NPOESS, 1996). However, there is far more to climate monitoring and research than simply collecting data (NRC, 1999a,b); the “culture” required for climate observation is fundamentally different from the one that obtains for short-term forecasts. The IPO has awarded two contracts for each of the candidate sensors. There have been final selections of the winning contractors in 1999 and 2000. The Ozone Mapping and Profiling Suite (OMPS) contractor was selected in early 1999. The “need date,” which is the date by which the first NPOESS platform must be ready to launch, is in 2003. However, the scheduled launch date is not until 2009. JOINT NASA/IPO PLANS NASA and IPO have begun plans for the NPOESS Preparatory Project, which would launch in 2005. The mission would support early flights of the Visible/Infrared Imager Radiometer Suite (VIIRS), the Cross-Track Infrared Sounder (CrIS), and the Advanced Technology Microwave Sounder (ATMS). Other small sensors also

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN may be flown. NPP will support early testing and evaluation of critical instruments and algorithms for NPOESS. Research requirements for selected NASA data sets have also been included in the NPP sensor requirements. The NPP mission may also demonstrate advanced technology options developed by NASA. Thus, NPP provides the opportunity to blend science and operational requirements while bridging between the first EOS series and NPOESS. INTEGRATING CLIMATE RESEARCH AT THE FEDERAL LEVEL At the federal level, the USGCRP was created as a “virtual agency”2 to coordinate the activities of NASA, NOAA, the National Science Foundation, DOE, and other agencies concerned with monitoring, predicting, or responding to potential changes in Earth's global environment. The cross-agency coordination of the USGCRP is conducted under the auspices of a subcommittee that reports to the White House-level National Science and Technology Council. Since its inception, issues related to global climate change have been identified as the highest priority for research coordinated through the USGCRP. However, recent NRC panels have faulted the USGCRP and/or agencies participating in the USGCRP regarding a variety of issues related to development of the required long-term observing and data management systems. 3 A recurrent theme in these reports is the enormous technical and programmatic difficulties in assembling a climate observing system based on research and operational assets. NASA, which has a particularly important role in the USGCRP, has announced its intention to devote greater resources to the study of “climate forcing, climate response, and the processes connecting the two.”4 However, NASA also acknowledges the necessity of exploring new arrangements with its USGCRP partners to develop a credible observing system suitable for climate research. Responding on behalf of NASA to the findings of the “Post-2002” report (NRC, 1999b), an official stated, The NRC Task Force noted appropriately that no single federal agency or administration is currently mandated to develop and operate for the appropriate period of time in the future, the full range of observations that are needed to understand and predict the behavior of the global Earth environment. NASA and NOAA simultaneously took the initiative to call the attention of the Executive Branch to this problem and are currently engaged in consultations with the Office of Science and Technology Policy to lay the foundations of a federal policy on this matter.5 The Pathways report overview (NRC, 1998a), based on the NRC Committee on Global Change Research assessment of the USGCRP, emphasized the critical nature of high-quality, long-term observations of the Earth system from both a scientific and public policy perspective. NPOESS and EOS are critical elements of this strategy, but the need to observe decadal and longer-term changes raises basic issues of observing system design and management. 2   “Virtual agency” refers to the USGCRP interagency body. See p. ii in USGCRP (1997). 3   For example, the Pathways report (NRC, 1998a) noted that “correctly transferring . . . key aspects of the observing program for USGCRP to operational programs will be very difficult.” The Climate Research Committee (NRC, 1999a) in its report The Adequacy of Climate Observing Systems stated that “there has been a lack of progress by the federal agencies responsible for climate observing systems, individually and collectively, toward developing and maintaining a credible integrated climate observing system.” The “Post-2002” report (NRC, 1999b) determined that “ensuring continuity of operational data, evaluating the readiness of a given ‘research' data series to move to an operational status, and managing the ‘research-to-operations' transition of data are problems that will require scientific community involvement and NASA leadership among the USGCRP agencies. ” In its report The Atmospheric Sciences: Entering the Twenty-First Century, the Board on Atmospheric Science and Climate (NRC, 1998b) noted that “. . . a comprehensive climate research program that serves societal needs is clearly within our grasp.” 4   “Understanding Our Home Planet: NASA's Role in Studying Global Climate Change,” remarks of NASA Administrator Daniel S. Goldin to the 80th Annual Meeting of the American Meteorological Society, January 9, 2000. 5   “NAS/NRC Review of NASA's Plans for Post-2002 Earth Observation Missions,” briefing by NASA to Board on Atmospheric Sciences and Climate, Woods Hole, MA, June 29, 1999. See also letter from Mr. Daniel S. Goldin, Administrator of NASA, to Dr. Neal Lane, Director, White House Office of Science and Technology Policy, February 1, 1999.

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN IDENTIFYING RELEVANT ISSUES: REVIEW OF EIGHT MEASUREMENT SETS Issues related to the development of a coherent national strategy for climate observations are addressed in this report in the context of a subset of measurements of demonstrable importance to climate research. With the emergence of NPOESS, the increased interest in NASA collaboration with operational agencies, and recognition of the importance of observations for climate research and policy, there is an opportunity to build the space-based component of a climate observing system. In collaboration with NASA, these requirements can be extended and refined so that it will be possible to begin to assemble credible time series of climate-related variables. In Chapter 2, Chapter 3, Chapter 4, Chapter 5, Chapter 6, Chapter 7, Chapter 8 through Chapter 9, the committee reviews eight Earth science data sets, discussing each in terms of its value for climate research and the associated requirements. The committee reviews the current status of these measurements and their associated algorithms, and also explores what the status of the requirements might be in 20 years (roughly at the end of the planned NPOESS program), when new technologies or new sampling strategies may have enhanced current data sets or enabled the delivery of new data products. The committee emphasizes that these eight measurement sets, although critical for climate research, are not necessarily the most important. Instead, the committee reviews these measurement sets to elucidate the scientific and programmatic issues associated with the integration of research and operational systems. The eight variables were selected because they span a broad range of science issues and also because of the range of the strategies for their implementation. The first three (atmospheric sounding, sea surface temperature, and land cover) have been part of the operational POES program for decades. Each data set has been used in climate and global change research as well as operational programs. The second three (ocean color, soil moisture, and atmospheric aerosols) have been part of the NASA research missions and are proposed for inclusion in NPOESS. These variables have not been measured as part of a long time series but on single missions instead (e.g., ocean color) or else the data product is still in development (e.g., aerosols). The final two variables (stratospheric ozone and Earth radiation budget) have been part of a long series of research missions (e.g., TOMS), and although there are counterparts in the operational missions, the Earth science community has focused primarily on the research missions. For each of the three sets, there are planned improvements in EOS. For each variable, the committee reviews current NASA and NPOESS plans for data collection and briefly discusses the primary sensors and their expected performance. (For some variables, international or commercial data sets may be relevant as well.) It also evaluates observing strategy in terms of data continuity and the types of data products that will be developed, and it compares strategies for calibration and validation6 with the plans currently laid out for the relevant NASA and NPOESS missions. Reconciling the sometimes conflicting requirements of operations and research is a difficult task, and attempts to develop a coherent, comprehensive observing strategy often have relied on ad hoc solutions. With changes in schedules, in program structure, and in fiscal resources, it has been difficult to maintain effective coordination for a sufficient period of time. For each measurement set examined in the following chapters, and in its summation in Chapter 10, the committee highlights those areas where investments or changes in management structure may help us to realize the potential for an integrated observing system for climate research. REFERENCES Keeling, C.D., J.F.S. Chin, and T.P. Whorf. 1996. Increased activity of northern vegetation inferred from atmospheric CO2 measurements. Nature 382: 146-149. Integrated Program Office (IPO), National Polar-orbiting Operational Environmental Satellite System (NPOESS). 1996. Integrated Operational Requirements Document (IORD) I. Joint Agency Requirements Group Administrators. 61 pp. + figures. National Oceanic and Atmospheric Administration (NOAA). 1997. Climate Measurement Requirements for the National Polar-orbiting Operational Environmental Satellite System (NPOESS), Workshop Report, Herbert Jacobowitz (ed.), Office of Research and Applications, NESDIS-NOAA, Washington, D.C. 6   Calibration is the process of quantitatively defining the system responses to known, controlled signal inputs, and validation is the process of assessing by independent means the quality of the data products derived from the system inputs.

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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN National Research Council (NRC). 1995. Earth Observations from Space: History, Promise, and Reality. Washington, D.C.: National Academy Press. National Research Council (NRC). 1998a. Overview, Global Environmental Change: Research Pathways for the Next Decade. Washington, D.C.: National Academy Press. National Research Council (NRC). 1998b. The Atmospheric Sciences: Entering the Twenty-First Century. Washington, D.C.: National Academy Press. National Research Council (NRC). 1999a. The Adequacy of Climate Observing Systems. Washington, D.C.: National Academy Press. National Research Council (NRC), Space Studies Board. 1999b. “Assessment of NASA's Plans for Post-2002 Earth Observing Missions,” short report to Dr. Ghassem Asrar, NASA's Associate Administrator for Earth Science, April 8. National Research Council (NRC). 2000. Reconciling Observations of Global Temperature Change, National Academy Press, Washington, D.C. U.S. Global Change Research Program (USGCRP). 1997. Our Changing Planet: The FY 1998 U.S. Global Change Research Program . U.S. Global Change Research Program Office, Washington, D.C. Willson, R.C., and H.S. Hudson. 1991. The sun's luminosity over a complete solar cycle. Nature 351: 42-44.