Demonstration Division

Of the five people in the branch, three are involved with the day-to-day operations and monitoring tasks related to the hardware and communications aspects of the network. They also coordinate all field repair and maintenance activities, interact with field personnel, and log all significant faults. Another person monitors the meteorological data quality from the NPN, and yet another handles all financial aspects related to the continued operation of the NPN, including tracking land leases, communications, and commercial power bills for more than 30 profiler sites. All five continue to work with others in the division to support the operations and maintenance of the NPN, resulting in consistently high data availability statistics for the past six years. The high quality upper-air and surface observations are distributed in real time to a wide range of users, such as NWS forecasters and numerical weather prediction modelers.

A very important component of the Network Operations Branch is the logging of all significant faults that cause an outage of profiler data. The duration of each data outage is broken down into many different states, including how long it took to initially identify a failure, diagnose and evaluate the problem, wait for repair parts to be sent and received, restore commercial power or communications, and when and how the fault was ultimately repaired. Analysis of these states reveals important information regarding operation of the network, as shown in the examples below.

Each profiler site's mean time between failure (MTBF) over the most recent, nearly five-year period is shown in Figure 26. Also shown are the maximum time (days) between failures (MaxTBF) and the total number (count) of failures for each site, including all data outages (i.e., power and communications, not just profiler hardware) lasting longer than 24 hours. The "better" sites are shown toward the right-hand side of the figure, with many operating longer than one year without an outage.

The NPN, currently noncommissioned by the NWS, is routinely monitored by personnel in the Profiler Control Center (PCC) only during normal working hours, 8:00 AM – 5:00 PM during the week (27% of the total hour in a week). The remainder of the time, the profilers, dedicated communication lines, and Hub computer system operate while unmonitored and unattended. Figure 27 shows the distribution of downtime (normalized over the past four years). Generally more than 50% of downtime was due to waiting for parts to arrive or for a repair person to arrive at the profiler site. Thus, it was determined that increased staffing of the PCC would have little impact on improved data availability; however, additional NWS maintenance staff would improve response time.

Figure 28 shows the total number of hours of profiler data lost by fault type (such as component failures, scheduled downtime for maintenance, and power and air conditioner failures) from 1 January 1996 – 1 October 2000. A further breakdown, by fault disposition, is shown in Figure 29. This information is monitored for trends that may be causing outages. The Fault Disposition Category indicates the corrective action that was required to restore normal profiler operations for each data outage in the past two years, and the number of hours of missing data attributed to each fault category. The largest category by far is the "Line Replaceable Units (LRUS) Replaced." This simply means that a piece of hardware, an LRU, had to be replaced to restore operations, along with the associated waiting time for a technician to respond to the site. The next largest category to restore operations is "Scheduled Down Time (SDT) Completed." This typically means that preventive system maintenance or antenna measurement/repair activities were completed. Note the significant number of lost hours of data attributed to the local breaker (main 200 amp) being tripped to the opposition, usually caused by lightning related power surges, and only needing to be reset. From this analysis, the Engineering and Field Support Branch designed and installed the capability to remotely reset the main breaker at each site. The Network Operations group routinely uses this method to restore profiler operations, as well as "power cycling" a site to sometimes clear other problems. The next largest category, "Profiler Maintenance Terminal (PMT) Restart," is activated to restore operations. This outage is typically corrected by logging into the profiler's computer from the Profiler Control Center in Boulder and reentering critical system parameters that have been corrupted, or simply restarting the profiler's data acquisition cycle. Each profiler must have a current Search and Rescue Satellite Aided Tracking (SARSAT) inhibit schedule in order for the transmitter to radiate, and for the profiler to measure the winds. This inhibit schedule (the smallest category in Figure 29) expires very rarely, usually because of an extended primary communications link outage, causing the profiler's transmitter to shut down as a fail-safe mechanism to prevent possible interference to the SARSAT system.

The branch has made significant improvements in its ability to remotely monitor activity within the NPN via the World Wide Web. Activities that are now routinely monitored on the Web include information on profiler real-time status, data flow to the NWS Gateway, and ingest of profiler data into the Rapid Update Cycle (RUC) model at the National Centers for Environmental Prediction (NCEP).

A significant improvement was made to the quality control algorithm, primarily affecting the three Alaska profiler sites. The algorithm allows the removal of very specific radial velocities that come from multiple trip ground clutter returns. Overall data quality has been greatly improved.

The Bird Contamination Check algorithm, developed nearly five years ago within the division, was modified. The original algorithm analyzed only the north and east beams to detect the broader spectral widths caused by migrating birds. Now the spectral width from the vertical beam has also been incorporated into the algorithm. Although the spectral width bird signature is not as broad in the vertical beam, it is still apparent and improves the algorithm's detection ability.

Staff continue to evaluate the Radio Acoustic Sounding System (RASS) for temperature profiling. When the Neodesha, Kansas profiler was recently relocated, the planned addition of RASS was a primary consideration in selecting the new site.

An improved wind and RASS data quality control algorithm has been investigated, and is being designed primarily to detect and correctly flag data contaminated by internal interference.

Additional lower tropospheric (boundary layer) profiler data will be acquired from targets of opportunity around the country. Staff will also continue adherence to sound operating principles that have produced high data availability rates.

Through agreement with the National Weather Service (NWS), their electronics technicians perform most of the preventive and remedial maintenance. At the PCC in Boulder, staff use the profilers' remote diagnostic capabilities to detect failed components, order Line Replaceable Units (LRUs), and coordinate with the NWS electronics technicians to carry out field repairs. A team of specialized engineer/technicians, called rangers, who are experienced in the design and operation of the profiler systems, handle the more complex problems. As division employees based in Boulder, the rangers can be mobilized to repair the profilers on short notice.

Alaska Profiler Network – The branch was involved with the transition of the Alaska profilers to the NWS. A Memorandum of Agreement was signed in 2000 by NWS headquarters, the NWS Alaska region, and the Office of Oceanic and Atmospheric Research/FSL for the implementation, support, maintenance, and operation of the profilers. NWS headquarters is providing coordination and support for the Alaska Region, and intends to use the three 449-MHz Alaska profilers as operational systems. FSL will continue to operate the profilers as part of the NPN, and the Alaska Region will assume responsibility for onsite maintenance, logistics, and funding of these systems.

The Alaska 449-MHz Profiler Network became operational in October 1999, and has recorded data availability to the NWS of over 90% since June 2000, and over 98% since August 2000 (Figure 30). When the Alaska profilers became operational, the wind profiles in the first five to seven range gates were corrupted due to receiver saturation. A delay of the transmitted pulse through a band pass filter in the transmitter caused a timing problem, whereby the receiver turned on while the RF pulse was still being transmitted. To solve this problem, the signal processor was reprogrammed to send the transmitted pulse sooner to compensate for the delay in the band pass filter. To ensure the integrity of the range gates, a calibration was performed before and after corrective action was taken.

Accumulation of snow on the antennas in Alaska has caused some loss of data. The Talkeetna and Central profilers have experienced problems when large amounts of snow build up on the antenna and the temperature rises above freezing. The snow melts and then refreezes causing the antennas' electromagnetic pattern to become distorted with high side lobes and thus degrading the data. It is interesting to note that when the snow pack is dry and consistent, it has no effect on the antenna pattern. The Alaska electronics technicians have had to remove the snow from the Talkeetna antenna twice this year and once from the Central antenna.

Minor ground clutter problems have also occurred with the Alaska profilers. When the antennas were installed, they were raised higher than usual off the ground for easier maintenance. This caused the antenna to be closer to the top of the security fence, apparently making it more susceptible to ground clutter. The security fence seems to perform a dual purpose, also acting as a clutter fence to eliminate ground clutter. Experiments with a higher fence will be conducted in the spring to help diminish the clutter problem.

Profiler Site Relocation – The Neodesha, Kansas, profiler was relocated because the site's landowner changed and that location was unsuitable for the Radio Acoustic Sounding System (RASS) operations. A new site was found about six miles from the original site and relocation was completed last September. Although the move only took one week, data were not available for a month because a component failed and the site was in checkout mode for quality assurance.

Equipment Upgrades – In response to an NWS Service Assessment report following the 3 May 1999 tornado outbreak in Oklahoma, which stated that "The NWS should make a decision on how to support the existing profiler network so that the current data suite becomes a reliable, operational data source," all NPN profiler sites have been outfitted with a remote-control main breaker (Figure 31). Profiler main breaker trips are the second largest contributor to site downtime. In most cases, main breaker trips are caused by AC power fluctuations or power surges during storms. Although the site usually does not sustain any damage from these occurrences, data availability remains down until a site visit is made to reset the main breaker. To address this problem, the main breakers at all profiler sites were replaced with ones that can be controlled remotely using a touch-tone phone. This capability reduces expenses and increases data availability by eliminating the need for a technician to visit the site to simply reset the main circuit breaker.

Other NPN Sites – The branch will continue providing prompt field repairs, appropriate coordination of network logistical support, and economical equipment upgrades to provide the meteorological community with quality NPN data. A continuing effort involves outfitting sites with wind and temperature profile capability, along with water vapor and surface meteorological measurements. Currently, 9 out of 35 sites are configured with RASS, and plans are to install these units at the Neodesha, Kansas, and Jayton, Texas, sites within the next year.

Two types of surface meteorological instruments, the Profiler Surface Observing System (PSOS) and the GPS Surface Observing System (GSOS), are now located at each profiler site. Plans are to replace these two units with one digital system, PSOS 11, at all profiler sites.

The grounding and lightning protection at all sites will be evaluated and upgraded to safeguard against lightning strikes. Existing ground networks will be tested and refurbished if necessary. Communications equipment, profiler components, and computers will be protected to isolate them from the damaging effects of lightning strikes.

A recently implemented strategy concerns the development of new software to support future operations of the NOAA Profiler Network (NPN) and its infrastructure. A process reengineering effort during Fiscal Year 2000 indicated that a more effective way to view the NPN of the future is as a set of platforms offering convenient power and communications at which to install meteorological measuring equipment for both operational and research purposes. This strategy drives software development efforts in three areas: migrating profiler operations to the National Weather Service (NWS), continuing to support the record-setting reliability and availability of the NPN data, and becoming the prime focal point on the Web for profiler data.

The branch was directly responsible for enabling NPN data availability and reliability to reach new heights during the fiscal year. In collaboration with the NWS, a monitoring system was implemented so that NWS electronics technicians could begin diagnosing profiler problems with limited support from the Profiler Control Center (PCC). In operation at the NWS Telecommunications Gateway, this system observes the delivery of wind profiler data from the NPN hub. If data are interrupted at a particular profiler, the system delivers a message via AWIPS to the NWS forecast office responsible for maintaining that site. The electronic technician may then diagnose the problem and initiate any action deemed necessary.

A "process reengineering" task was completed that involved documentation of the operations of the PCC, NPN hub, and NPN instrumentation. In this vital task, the computer captures the processes and systems so that their requirements can be extracted and documented, and then used to engineer new systems needed to accomplish goals. Using these requirements, branch personnel began to develop and test a "software toolkit" consisting of low-level software objects that will become the foundation for accelerating efforts in Fiscal Year 2001.

During 2000, staff serviced an average of 18,000 Web hits per month. Thirty percent of these Webpage views were from nongovernmental sites with network domains of ".net" and ".com." For the first time, raw profiler data were made available via the web. Significant amounts of internal operational documentation were converted to the Web and placed on the division's Intranet site. Informational materials (e.g., the "Facts Fax Bulletin" and the "Chiefs Report") formerly distributed via fax or e-mail were also converted to the Web.

The first phase of transition to NWS operations consists of altering the delivery mechanism for data acquired at NPN sites. The data are now delivered in five composite bulletins, each containing information from up to eight different sites. When one of these sites is unable to deliver data via landline, the entire bulletin is delayed until it can be transmitted via the backup communication system that uses the GOES satellites. This delay sometimes affects regular delivery of data to the numerical models operating at FSL and the National Centers for Environmental Prediction (NCEP). Beginning this spring, a single message will be sent from each type of measuring instrument, per site, per time period to alleviate the delays caused by message formatting. Part of this phase also includes collaboration with NWS regional and headquarters personnel, as well as with other FSL divisions, to produce decoders so that data in the new formats can be accessible on AWIPS.

A prototype of the Wind Profiler Processing Platform (WPPP), which will break the time-based dependency between the Lockheed-Martin manufactured wind profiler and the GOES Data Collection Platform (DCP), will be in place this year. This is important because the manufacturer of the particular GOES DCP for which the profiler was engineered is no longer in business. Additional functions of the WPPP will include moving quality control processing to the actual site, becoming a central collection platform for other collocated instrumentation such as GPS water vapor and RASS, and collecting data for the diagnosis of faults occurring in the collocated instrumentation. The WPPP will produce data ready for display on AWIPS and in a format ready for routing by the NWS and Global Telecommunications System.

The second phase of the transition is installation of a WPPP in the three Alaskan network sites, the addition of the WPPP to the database of Line Replaceable Units (LRUS) for NPN wind profilers, and training for NWS personnel, all to be completed in mid-2002.

The third and final phase involves installation of a WPPP at each remaining profiler site, again with training and documentation for NWS personnel. The upgrade of the network to an operating frequency of 449MHz will also be completed.

The branch will also be working on a joint project between the NWS and the University of Northern Florida to demonstrate the feasibility of remote wireless communications for meteorological measuring instruments. This project will also exemplify new technology including independent "smart" sensors and self-configuring networks.

In 2001, the staff will continue to look for opportunities to use the Web to make operations more efficient and cost effective. The division's Website will be improved in both appearance and operation. It will also be hosted on more modernized hardware, and will use new Java and other current software technologies.

To accomplish these goals, the branch collaborates with other NOAA organizations, government agencies, and universities to develop a 200-station demonstration network of GPS-Met observing systems by 2005. These collaborations allow the division to build, operate, and maintain a larger network of observing systems with lower cost, risk, and implementation time than would otherwise be possible using laboratory and division resources alone. The cornerstone of this effort is a "dual-use paradigm" within the federal government that allows leveraging of the substantial past and current investments in GPS made by other agencies such as the U.S. Coast Guard (USCG) and Federal HighWays Administration (FHWA) for purposes such as high accuracy surveying and improved transportation safety. From a technical standpoint, this is possible because of a fortuitous synergy between the use of GPS for precise positioning and navigation, and meteorological remote sensing. The branch is also taking advantage of the substantial effort that NOAA's National Geodetic Survey (NGS) has made to establish a growing network of Continuously Operating Reference Stations (CORS) in the Western Hemisphere. The CORS program collects, archives, and disseminates the GPS observations made by numerous organizations, including FSL, and distributes them to the general public. The branch contributes GPS and surface meteorological data acquired at 56 NPN and other NOAA sites. In fact, the fourth most requested dataset in the CORS network currently comes from the GPS-Met system on the roof of the David Skaggs Research Center in Boulder, Colorado (Figure 33).

For the past three years, the branch has been collaborating with the Scripps Orbit and Permanent Array Center (SOPAC) at the Scripps Institution of Oceanography, and the School of Ocean and Earth Science and Technology (SOEST) at the University of Hawaii at Manoa, to develop real-time orbit and data processing techniques for NOAA. The effort has resulted in the first-ever practical implementation of real-time GPS meteorology (GPS-Met). By the end of Fiscal Year 2000, GPS-IPWV observations with millimeter-level accuracy were being made at 56 sites every 30 minutes with about 20-minute latency. The realization of real-time GPS-IPWV for objective weather forecasting (near real time for subjective applications) with no significant loss of accuracy compared with those achieved using post-processing techniques is the last major milestone in the 1994 GPS-Met Project Plan to be achieved.

To accomplish real-time GPS-Met, three things had to be achieved: accurate satellite orbits had to be available in real time, and ways to acquire and process GPS data from an expanding network of sites in the shortest possible time had to be developed, as follows.

Confirmation of GPS-IPWV Accuracy – Figure 36 shows a comparison between near real-time GPS-IPWV calculated every 30 minutes and static (24-hour) solutions during qualification testing of the new real-time data processing technique in April and May 2000. Comparisons number 2050, with a mean difference of 0.20 mm and a standard deviation of 1.02 mm of delay. This translates to an average difference of about 0.03 mm IPWV +/- .15 mm IPWV.

In September 2000, the branch participated in its third water vapor intensive observing period (WVIOP) experiment at the Department of Energy's Atmospheric Radiation Measurement (ARM) facility near Lamont, Oklahoma. The major difference between this WVIOP and previous ones was the availability of near real-time GPS-IPWV data to support on-the-fly comparisons with other instruments. Preliminary results indicate that GPS-IPWV measurement error is closer to 3.5% than the previous estimate of 5% that was determined in 1997. Figure 37 is a comparison of near real-time GPS data and rawinsonde measurements during WVIOP 2000.

GPS-IPWV Impact on Weather Forecasts

Evaluations of the impact of GPS-IPWV observations on weather forecast accuracy have been conducted by the Regional Analysis and Prediction Branch of FSL's Forecast Research Division since 1997. In 2000, a previously undetected problem with the assimilation of GPS data into the Rapid Update Cycle (RUC) was corrected, and all of the GPS-IPWV observations from 56 sites were made available to the 60-km RUC for parallel runs (with and without GPS). Table 1 summarizes the results, which shows that improvements in 3-hour relative humidity forecasts using the 60-km RUC NWP model with GPS observations in parallel cycles using optimal interpolation are greatest at the lowest levels and sensitive to the number of stations in the network. Table 2 shows the results for the lowest 2 levels, 850 hPa and 750 hPa.

Expansion of the GPS Water Vapor Demonstration Network

An agreement between OAR/FSL and the Department of Transportation's Federal HighWays Administration (FHWA) was signed this year that allows the installation of NOAA GPS Surface Observing System (GSOS) packages at all Nationwide Differential GPS (NDGPS) sites. There will be about 70 NDGPS sites in the water vapor demonstration network by 2004.

The branch added three sites to the network in 2000: one at the Nationwide Differential GPS (NDGPS) site at Driver, Virginia; a second at the last NPN site to receive a GPS water vapor observing system, Slater, Iowa; and the last at the Ground Winds Lidar facility at Bartlett, New Hampshire, operated by the Mount Washington Observatory. Figure 38 shows the network at the end of Fiscal Year 2000, along with stations identified for inclusion in 2001. A total of 56 sites were delivering data at the close of the year.

The branch will work with various FSL divisions and NCEP to make GPS-IPWV data available to the wider NOAA forecaster and modeler communities, and will work with others in FSL to display GPS-IPWV on advanced NOAA workstations including FX-Net, W⁴, and AWIPS.

Another collaborative effort involves the UCAR SuomiNet program to add some of their sites to the NOAA/FSL GPS Water Vapor Demonstration Network. Of special interest are sites owned by the University of Oklahoma in and around the ARM site, and one belonging to Plymouth State College in New Hampshire.

In cooperation with the NWS forecast offices in Florida, branch staff will determine if GPS-IPWV data can improve weather forecasts during the convective storm season. This will be accomplished by working with Florida Department of Transportation (FDOT) and the NWS forecast offices to install FDOT differential GPS receivers at all forecast offices in Florida, add the sites to the Water Vapor Demonstration Network, and retrieve, process, and provide the data to the forecasters in near real time. Plans are to work with the 45^th Weather Squadron at Patrick Air Force Base and NASA at Kennedy Space Center to density the GPS network in the Cape Canaveral/KSC area, and help them to use these data to address their primary weather challenge: lightning predictions.

The branch will collaborate with the NASA Langley Research Center (LARC) on the Clouds and the Earth's Radiant Energy System (CERES) project, a high priority NASA satellite program which has several important goals. The branch's involvement will be to assist LARC to install a GPS-Met system on an offshore ocean platform, and provide them with accurate water vapor data in near real time. Since water vapor is a significant forcing function in radiative transfer processes within the atmosphere, GPS-IPWV data will be used to constrain their models of the incoming and outgoing shortwave and longwave radiation within the atmosphere.

For calendar year 2000, the payoff in efforts taken to eliminate single points of failure and minimize downtime and risks resulted in the uptime for the NPN processing systems averaging 99.3%, communications systems uptime averaging 96.8%, and data delivery to the National Weather Service (NWS) averaging 94.4%. Data delivery to NWS in calendar year 2000 improved by more than 4% over calendar year 1999 (effective improvement of approximately 5%). A summary of profiler data availability for 2000 is shown in Figure 39.

Telecommunications risks and costs were minimized by requesting an exception to FTS-2001 for NPN data circuits. Department of Commerce approval of this request was obtained, and telecommunications services through AT&T were retained. This permitted continued use of existing local division equipment valued at approximately $130,000, ensuring continuous reliable NPN telecommunications services. A savings of approximately $750,000 over five years, compared to proposals for similar services by FTS -2001 providers, will be achieved using the existing AT&T equipment and circuits.