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New Observation Systems The key new observation systems in the NWS modernization are the Next Generation Weather Radar (NEXRAD), the Automated Surface Observing System, and the Next Generation Geostationary Environmental Satellites, which were described briefly in Chapter 1. The following sections contain a preliminary assessment of these systems; the Committee will provide additional assessments as the programs evolve. Other observational systems may contribute significantly to the modern- ized NWS. Two particularly important ones for forecasting and warning of severe weather events, because of the high space or time resolution of their observations, are wind profilers and a sferics network for lightning detection and analysis. A network of profilers will be tested during the Modernization and Associated Restructuring Demonstration (MARD) to be conducted in the midwestera United States around 1993. The results of the MARD will contribute to a future decision on operational implementation of profilers in the NWS. A private national lightning network now exists and is used by the NWS under a contract that expires in March 1991. The NWS has initiated a competitive procurement action for the collection of lightning data through the MARD period. NEXT GENERATION WEATHER RADAR The first network Next Generation Weather Radar (NEXRAD; techni- cally, the WSR-88D) has been installed near Oklahoma City. Another is located at the NEXRAD Operational Support Facility (OSF) in Norman, Oklahoma and will remain an OSF resource for use in testing, evaluating, and Sferics refers to a radio direction-finding system used to detect and locate lightning by means of the "atmospherics" (electromagnetic radiation) produced by lightning discharges. 21

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enhancing the NEXRAD system. The rate of installation had been planned to increase gradually to one per month by the end of 1991, then eventually to four per month in 1994. Originally, a period of one year had been planned between installation of the Limited Production Phase radars and initiation of the full production phase, to allow for a thorough and complete operational evaluation. No time is currently available because of slower-than-anticipated progress in the early phases of procurement and software development problems. Thus final testing and evaluation must take place in 1991, just prior to acceptance of the NEXRAD systems at the OSF and Oklahoma City. However, neither the installation of the radar nor the engineering acceptance of the system establishes that it is actually operational in the meteorological sense. That happens, as is the case for all new elements in the NWS modern- ization, when the radar is operationally ready and is certified to be fully commissioned after training of the local staff. Status of Major Components of the Next Generation Weather Radar Program Experience with NEXRAD units suggests that the hardware (transmitter, receiver, signal processor, and antenna) is robust and will prove to be reliable in the long term. There were reports of poor reliability during the NEXRAD Initial Operational Test and Evaluation, Phase II (IOT&E-2) (Air Force Operational Test and Evaluation Center, 1989). Some of this resulted from the fact that no changes, improvements, or fixes to the system were permitted during the approximately five-month IOT&E-2 process. Because of that constraint, repetitive failures of the same nature occurred throughout the pro- cess during which corrective actions were not allowed. This is not a criticism of the process, but merely a recognition of the fact that in a normal opera- tional environment, appropriate corrective actions would have been taken and maintenance procedures revised. The IOT&E-2 process involves independent test and evaluation of the entire NEXRAD system to determine its operational effectiveness and suit- ability, to identify its deficiencies and enhancements, and to determine which items should be addressed during subsequent tests and evaluation. Following are additional comments based on the IOT&E-2 report regarding functional performance and capability, human engineering, software documentation and maintenance, and training. In the category of functional performance and capability, significant prob- lems were encountered regarding the ability of the radar to generate auto- matically critical derived data reliably. These include, for example, effective range unfolding and error-free velocity dealiasing. A software error in the system prevented the range unfolding algorithm from working correctly, and 22

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the algorithm for velocity dealiasing was inadequate. An improved velocity dealiasing algorithm, similar to that being used in the Terminal Doppler Weather Radar application for the FAA, is being installed and the range unfolding software error has been corrected. It is now likely that a highly reliable algorithm for hail detection and quantitative hail measurement will not be available initially, but research at the National Severe Storms Laboratory of NOAA is expected to produce an improved technique. Also, the National Severe Storms Laboratory is working on an unproved mesocyclone detection algorithm. These problems are not surprising; the development of the NEXRAD system was deficient in not providing for adequate prototype demonstrations in an operational environment similar to the experiments and programs that were undertaken as part of the Terminal Doppler Weather Radar develop- ment for the FAA. Nevertheless, the Committee is confident that these deficiencies can be corrected. Upgrades to the Next Generation Weather Radar Technical Requirements Another group of comments in the Initial Operational Test and Evalua- tion, Phase II (IOT&E-2) report dealt with human engineering aspects of the system. Most result from inadequacies in the original NEXRAD Technical Requirements; they can be overcome, either through changes in the NEXRAD prime contract with UNISYS Corporation, or through enhance- ments developed by the Operational Support Facility (OSF). The IOT&E-2 report included a number of additional recommendations that also extend beyond the scope of the NEXRAD Technical Requirements. About one-half of the recommendations state that the System Requirement Review Board of the NEXRAD Joint System Program Office has referred certain matters to its Service Report Enhancement Committee for recommendations. It is presumably the responsibility of the Service Report Enhancement Committee to provide advice and recommendations regarding changes to system require- ments. As mentioned earlier, such changes would have to be implemented either by modification of the contract with UNISYS or by the OSF itself. The Service Report Enhancement Committee is appointed by NOAA, FAA, and the United States Air Force (USAF) to consider these recommendations and advise the NEXRAD Program Council.1 Presumably the NEXRAD Program The members of the NEXRAD Program Council are the Assistant Administrator of NOAA for Weather Services, the Commander of the USAF Air Weather Service, and the Deputy Associate Administrator of the FAA for National Airspace System Development. 23

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Council would then direct that specific enhancements, where appropriate, be implemented. Adequate direction and resources will be required throughout the life- time of the NEXRAD system to ensure the continuing development and operational implementation of new processing algorithms based on scientific developments and operational experience. Software documentation and maintenance is another important area. A number of the IOT&E-2 recommendations related to the system's software, its documentation, and its maintenance. Ultimate responsibility for system software maintenance rests with the OSF, and its leadership understands and accepts that responsibility. Training Another class of Initial Operational Test and Evaluation, Phase II (IOT&E-2) recommendations concerns training. In response, the NEXRAD Joint System Program Office and the NWS have adopted a revised approach to training NWS personnel. Training for system maintenance will take place in Kansas City, Missouri; training for system operations will take place at the Operational Support Facility (OSF) in Norman, Oklahoma. UNISYS will be responsible only for the initial training of NWS instructors (and perhaps for the first one or two operator courses). The NWS instructors will, in turn, be responsible for training weather service operational and maintenance person- nel. It is the Committee's understanding that the NWS instructors were selected carefully. A 14-week software course will be conducted at the OSF; UNISYS is also responsible for this course. UNISYS is currently placing considerable emphasis on its responsibilities for training and documentation, and has appointed new people for these tasks. Thus the training deficiencies identified in the IOT&E-2 report are being addressed. Whether the training will actually be effective is the subject of an evaluation process that will begin soon. Another issue related to training is continuing education. It appears that the OSF understands and is planning for its responsibilities related to initially training operators of the system and then to providing adequate training on system upgrades and changes as they occur. What is not explicitly included to date relates to procedural revisions. As the system matures, procedures are likely to change from time to time at many of the NEXRAD sites. It is essen- tial that the OSF standardize such changes and apprise operational staff of the most effective procedures for fulfilling its responsibilities. The NWS must develop comprehensive training and education programs such that its mainte- 24

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nance, operational, meteorological and hydrological staffs remain current. This must become part of its ongoing long-range plans. Outlook and Recommendations The current state of the development of the NEXRAD hardware is excellent. Its performance, even at this stage, gives great promise of providing a major improvement in forecasts and warnings. However, problems with completion of the operational software continue. As of December 1990, the initial operating capability software is not expected to be available until July 1991. Clearly, results of the definitive engineering tests, system functional evaluations, and system reliability evaluations that remain to be completed will be very important. An essential focus of the test and evaluation phase will be the performance of the software. The Committee cannot judge how well NEXRAD will meet its technical and functional requirements until this phase has been completed. Recommendation: Steps should be taken to ensure the continued development and improvement of Next Generation Weather Radar processing algorithms as new developments and operational experi- ence accumulate. Recommendation: The National Weather Service should develop a continuing comprehensive training and education program so that the skills of the Next Generation Weather Radar maintenance and opera- tional staffs, as well as the meteorologists and hydrologists, reflect the ever-changing state of the art. AUTOMATED SURFACE OBSERVING SYSTEM The Committee does not have any specific comments at this time regard- ing the status of the development and installation of Automated Surface Observing System (ASOS) units in the NWS modernization. Although the ASOS offers some clear advantages over the present surface observation method in operational weather forecasting and warning, serious concerns exist about its accuracy, representativeness, and system performance. The Commit- tee is also concerned about the quality and appropriateness of the ASOS data hi terms of continuing the climate record and monitoring climate change. This aspect is discussed in the last section of this chapter. Finally, NOAA has not addressed the need to augment ASOS data to maintain the climate data record. 25

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Need for Use of Adjunct Sources of Surface Observations The ASOS network of surface reporting stations will substantially increase the spatial resolution of the current surface reporting network, but even greater resolution will be needed for additional improvement in small- scale numerical forecast models (30 km horizontal resolution) being intro- duced by the National Meteorological Center. Although the observational resolution of Next Generation Weather Radar, the Next Generation Geosta- tionary Operational Environmental Satellites, and NOAA (polar orbiting) satellites is compatible with these models, quantitative surface observations are also required. Therefore, an era is beginning in which local and state observa- tions (e.g., the Illinois State Water Survey network or the Oklahoma Climate Survey network) will become increasingly important as a cost-efficient means of improving forecasts and warnings of small-scale weather events. Also, the use of these data to verify high-resolution forecasts undoubtedly will contrib- ute to even further improvements as systematic model errors and errors from highly localized effects are uncovered and corrected. Recommendation: The National Weather Service should identify other local and state surface observation resources; assess their quality and utility for operational use as adjunct data; prepare a national summary of the nation's high-resolution observing capabilities; assess the cost of acquiring and upgrading the nation's high-resolution surface observing capabilities; initiate efforts to acquire existing data and, as feasible, to improve the quality and quantity of the data; and promote the development and installation of additional local and state networks in data-sparse regions. ENVIRONMENTAL SATELLITES The Next Generation Geostationary Operational Environmental Satellites (GOES-Next) will play a particularly important role in continuously monitor- ing clouds and weather systems from above and increasing the number of measurements of free atmosphere winds, temperature, and humidity, thus contributing to the improved small-scale, short-period forecasting and warning that is the primary focus of the NWS modernization and associated restructur- ing. Improvements now being developed in the free atmosphere temperature and humidity soundings acquired by NOAA polar orbiting satellites will also contribute to improved longer-range numerical forecasts. However, these developments are in the future. Today the nation has inadequate weather-observing satellites in orbit or available for launch to guard against the loss of satellite information owing to launch failure or delays 26

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in the construction of additional spacecraft. The GOES system now has only one satellite in orbit rather than the two required to fully cover the United States and adjacent ocean areas. This results from a launch failure at a critical time (GOES G in May 1986), as well as continued delays in the development of the GOES-Next spacecraft (GOES I through M).1 Although GOES 7 (launched in February 1987) is operating well, it will be five years old before the earnest first launch of the new series, GOES I, in 1992. The NOAA polar satellite system is in better condition with satellites in orbit, but continued funding constraints have forced delays in the availability of replacement satellites that certainly will be needed in the future. The GOES-Next delays resulted from serious problems in the development of two new instruments, a cloud imager and an atmospheric sounder, by ITT Corporation-Fort Wayne under a subcontract from the prime contractor, Ford Aerospace Corporation. Fortunately, development by Ford of the remaining parts of the spacecraft has gone well, but integration and testing can only proceed so far before the instruments being built by ITT are required. The delays have caused a major overrun in the Ford Aerospace prime contract to produce and test the satellites. The contract is being managed by Goddard Space Flight Center of the National Aeronautics and Space Administration (NASA) for NOAA, and all funds come from NOAA. Although NASA believes that the worst of the development problems have been solved and the principal task now is to keep instrument assembly and test efforts on schedule, the same confidence has been expressed in the past and unexpected difficulties have suddenly appeared, forcing additional sched- ule slippage. The overrun situation plus the limitations in funds available to NOAA in the past have resulted in stop work and slow orders on GOES K, L, and M. As a result, the Committee is concerned that reestablishment of the full two- GOES constellation may not take place until mid-1994 or later, should there be a launch or spacecraft failure with GOES I or J. Because the NWS modernization program depends on the GOES-Next satellites, along with the Next Generation Weather Radar, the Automated Surface Observing System, and the Advanced Weather Interactive Processing System, the fragility of the GOES program has the potential to delay the schedule for completion of the full modernization and restructuring. The spacecraft are designated serially by letter before launch; after successful launch into orbit, the letter is changed to a number representing the new satellite's position in the sequence of successful launches of that particular series of satellites (e.g., GOES H became GOES 7 after its successful launch). 27

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The NOAA polar orbiting satellite system is in better technical condition than the GOES system. However, funding constraints in the polar program also threaten continuity problems in the event of launch or premature satellite failure. It also should be noted that NASA now procures commercial launch services on behalf of NOAA, not just launch vehicles as in the past. This means that launch schedules will be far more difficult to change due to the requirements of other users of the launch services, which will make quick replacement of failed satellites even more difficult than before. Recommendation: The National Oceanic and Atmospheric Admin- istration, the Department of Commerce, the Office of Management and Budget, and the Congress should provide more realistic budgeting and funding for the National Oceanic and Atmospheric Administration's operational satellite systems in order to realize the full potential benefits of the National Weather Service modernization and associated restructuring. VIABILITY AND INTEGRITY OF THE CLIMATE DATA RECORD The nation's climate record is a valuable resource whose viability must be maintained. Climate information is used in a variety of analyses and applications of economic value and importance to safety. These include the design of structures, drought assessments, agricultural planning and assess- ment, and water management. The possibility of climate change as a result of human activity over the coming decades is another application; observa- tional strategies and capabilities must be developed that will provide a data record from which regional and global climate trends can be determined unambiguously. The requirements for these data have been considered by several national and international organizations (for example, see NRC, 1990b), and data programs are being planned or enhanced by a number of U.S. agencies (Committee on Earth Sciences, 1990). Climate data come from many governmental and nongovernmental sources; however, the NWS is the primary organization engaged in observing and recording in situ weather information in the United States. It must ensure the accuracy and integrity of the weather information it gathers to fulfill its operational requirements; however, the Committee is concerned about the adequacy of NWS data to meet NOAA's climate requirements. The NOAA (which includes the National Environmental Satellite, Data, and Information Service as well as the NWS) is responsible for the acquisition, integrity, storage, and timely availability of the weather and climate data it 28

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acquires, as well as a substantial amount of such data from other federal agencies and other nations. Modernization and restructuring of the NWS will affect the viability and integrity of the U.S. climate data record, but it will also provide the oppor- tunity to enhance this record significantly through new kinds of data not formerly available. For example, Next Generation Weather Radar data can be used to derive improved estimates of time-integrated precipitation over most of the United States, an important dimatological parameter. Also, the wind profiler data, because of the high frequency of observation, could provide new information on wind spectra. These and other opportunities to enhance the climate record should be examined by NOAA. The most direct impacts of the NWS modernization and restructuring will arise from changes in observing locations and instrumentation. Changes of observing locations generally induce changes in climate statistics that are larger than those arising from climate variability. Changes in instrumentation pose problems of consistency and accurate calibration between old and new sensors. In the case of automated remote measurements, these problems include the lack of manual supervision of equipment, as well as the lack of direct viewing of weather events that are an integral part of the climate record such as statistics regarding summertime convection, distant thunderstorms, lightning, virga, and variable sky conditions. Because the NWS has traditionally viewed its role as collecting observed data primarily to prepare forecasts and warnings, data quality has been deter- mined largely by these needs. However, the accuracy, continuity, and consis- tency required of observed data may depend on whether the data are to be used in forecasting or climate research. For example, a slight shift in the loca- tion of a thermometer will have little effect on weather forecasts but often produces a noticeable discontinuity in average temperatures at a station, which clearly makes determining climate trends difficult. Given the evident need for high-quality data for climate studies and applications, the Committee argues that the NWS must be concerned that its data satisfy the needs for consistent climate records as well as for forecasting. The record should be as free as possible from avoidable bias. The slight additional costs are more than justified by the importance of the climate- related policy issues that the nation will face. Because NWS modernization plans give little attention to the issues of data management and the quality of the climate record, the Committee recommends the following: Recommendation: The National Oceanic and Atmospheric Admin- istration should set the requirements for the climate data to be derived 29

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from the modernized National Weather Service observations, establish the role of the National Weather Service in generating these data, and ensure the availability of the resources necessary for this purpose. The National Weather Service at all levels should recognize its responsibility to acquire a major portion of the national climate record; the preservation of data quality for climatic purposes should have equal priority with its mission of providing forecasts. Recommendation: Criteria for the accuracy of the various data collection systems should be selected carefully with attention both to the needs of the National Weather Service and to the quality of the climate record. Limits on both random and bias errors for data sys- tems should be determined by the requirements of science rather than by the technology of the measurement. Recommendation: When new instruments are brought into operation, there should be proof that their observations are within well-defined limits of the observations over the range of the record provided by the instruments they replace. This will require that new and old systems be operated simultaneously in an operational environment, for at least one year, at many locations around the country. Ideally, this simulta- neous operation should occur at every site where new equipment is installed. If the new equipment does not meet the requirements that ensure the integrity and viability of the climate record, then the National Weather Service must be prepared to modify it or find an alternative. Recommendation: When instrument sites are changed, simultaneous operation at the old and new sites should occur until adequate statis- tics on the difference of observations between sites can be developed. These statistics should be recorded carefully and made readily avail- able. Recommendation: Authority should be given to an individual or individuals at each site to question the accuracy of any observation system, and allowance should be made for that individual or those individuals to study the problem and recommend changes. The National Weather Service and its reward system should encourage individuals to ensure continuously the accuracy of data collection systems and of the climate record. Recommendation: The National Weather Service should establish a network of observation stations in natural and undeveloped areas with the sole aim of acquiring baseline data for a long-term climate record. Consistency of the record over long periods should be the first priority. Areas in which these stations are located must remain 30

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natural and undeveloped; national parks would be candidate sites. This network will fit within the current Automated Surface Observing System program with onfy modest additional cost. The Committee plans to continue its examination of the NWS modern- ization as it relates to the climate record to help ensure a positive impact on that record. 31