Wayman Baker (NOAA/NWS) opened the meeting and welcomed the participants to Key West. He noted that the Website for the working group is now accessible at: http://space.hsv.usra.edu/LWG/Index.html, and that the minutes of the Lidar Working Group meetings may be viewed there. He introduced Debra Hallmark, who requested electronic versions of all presentations that are to be included in the minutes of the current meeting be provided to her. Debra invited suggestions for relevant links to be posted on the website. All electronic correspondence relevant to the minutes should be addressed to: debra@space.hsv.usra.edu
Wayman proceeded to review the action items from the Summer 2001 (Frisco) meeting:
Gary Spiers, speaking on behalf of Chris Stevens (NASA New Millennium Program‚NMP), reviewed the status of the NMP and emphasized the technical road maps being developed as a result of a series of workshops. The intent is to roll these roadmaps into a plan for NASA Earth Science Enterprise/Earth Science Technology Office (ESE/ESTO) approval. Gary discussed some of the specific technologies, roadmaps, and targeted science, including deployable optics, advanced communications, and laser/lidar. The laser/lidar roadmap points to a DWL flying in 2010-2012. A roadmap for distributed platforms targets winds, too. Gary stressed that NMPís role is to demonstrate and develop technology, and to make sure that the technology gets used.
Bob Brown commented that one of the NMP roadmaps points to ocean surface winds. He suggested tightening this portion, since tropospheric winds and DWL represent new science and technology, but ocean surface winds and scatterometers are established.
Dave Emmitt asked whether and how the NMP and ESTO coordinate their activities. Frank Peri of ESTO replied that they do so, for example, via workshops. Peri promised that the DWL roadmap he planned to present at Key West would reflect opportunities for the NMP to play a role.
Jan Paegle (University of Utah) demonstrated the sensitivity of numerical weather prediction (NWP) to initial state uncertainty in selected upstream domains, using five-day forecasts made with the Global Utah Model. His goal was to gain insight with respect to the optimal spacing and location of distributed and enhanced observations. He reviewed the characteristics of the Utah model, and discussed data sets drawn from NCEP and ECMWF analyses. He noted that analyses are similar over NH land masses but diverge over oceans due to data voids.
Jan argued that while long waves have little initial state uncertainty, the fraction of forecast error in the long waves grows over time. A global observing system that properly characterizes the long waves will be the most useful for improving extended forecasts. Jan speculated that observation systems other than DWL (sondes, balloons, UAVs) might do a better job for regional forecasting. For example, North American targeted observations explain 90% of initial difference fields, but that fraction declines over time due to advection. After 30 h, the impact was roughly equal to that from North American targeted observations. North Pacific observations account for 70% of the five-day forecast impact relative to global observations for North America.
Jan pointed out that five-day predictions are not at the limit of predictability. So, he examined ten-day forecasts, too, and found that after about six days, the global observations are more important than those from the North Pacific. Finally, he considered the effect of wind versus temperature uncertainties. For ten-day forecasts, winds provide almost all of the predictability to be gained; temperature alone yields only ~ 1/3 of the impact of wind alone. (Wayman Baker noted this result is consistent with OSSEs conducted by Bob Atlas in the 1980's.)
Bob Brown (University of Washington) presented a talk entitled: Scatterometer vs. DWL: Friend or Foe? He commented that there are no tropospheric or PBL winds from satellites, and few in situ measurements, and even those have large errors associated with them. Bob lamented this state of affairs, given that general circulation models consistently show improvement when good wind initialization is available. For instance, scatterometers locate storm centers to within 25 km, while ECMWF may be off by as much as 150 km. Bob listed phenomena directly assessed or inferred using scatterometer data, and expressed concern that after SeaWinds II, NASA is not committed to another scatterometer, and a break in service may result.
Bob indicated that a PBL lidar could push science significantly in several areas. The difference in the footprint of a scatterometer and a DWL, he maintains, renders them complementary, not redundant.
Farzin Amzajerdian (NASA/LaRC) discussed development of a new mobile validation lidar facility at LaRC. The multi-purpose lidar trailer is called "Validar." It will feature a weather station, video cameras, and GPS as well as a state-of-the-art coherent 75 mJ Doppler lidar. The purpose is to facilitate validation of component technologies and signal processing techniques. It is to be flexible, allowing scanners, telescopes, and other subsystems to be integrated and tested. It may be used to develop calibration and validation procedures for a future space-based system. In addition, Farzin hopes to use the facility to validate aspects of atmospheric models and effects of the atmosphere on lidar signal and performance.
VALIDAR is built around a laser transmitter manufactured by Coherent Technologies Inc. The lidar is currently operational, although not all components are in place. The trailer facility includes a data analysis area and equipment as well as space for the instrument. Final integration is scheduled for September 2002, with the intention of becoming operational in October. Support has come from the IPO and various NASA offices.
Dave Emmitt asked what other lidars are available at LaRC for intercomparison. James Barnes listed several.
K. Asai (NASDA) reported on activities by the Japanese Space Lidar Group related to the development of a coherent lidar for the International Space Station /Japanese Experiment Module (ISS/JEM). The mission is intended to last one-year. Dr. Asai indicated that laboratory results encourage a 0.5 J amplifier demonstration. He reported both some progress and setbacks with laser development. A ground-based demo was underway in February 2002 with radar wind profiler for validation. Some wind profiles (horizontal components u and v components) had in fact been obtained by the time of the Key West meeting. Dr. Asai proceeded to show the airborne instrument and aircraft that are to be used for the subsequent airborne demonstration.
Dr. Asai explained that in Japan, NASDA, the ISAS, and the NAL are being merged into single space agency. This action will be official next year. The merger is causing uncertainty and resulting in problems. For example, the announcement of opportunity for ISS/JEM has been delayed from March 2002 to 2003 or 2004.
Dave Emmitt asked what experiments are planned for the aircraft. Dr. Asai replied that few atmospheric scientists have been involved in the planning; so far, they have concentrated only on a technical demonstration.
Bob Brown asked whether a letter of support from the Working Group to the merged Japanese space agency would be of benefit to the ISS/JEM. Dr. Asai expressed appreciation for all support that the international community can render.
Milt Huffaker of Coherent Technologies, Inc. (CTI) reported on progress with laser work at CTI. He noted CTIís ongoing work with the ISS, airports, airlines, and environmental safety. Although airlines and airports are now focused on security matters, military interest for tracking and ranging has soared. He discussed the ISS/JEM amplifier work being done by CTI, noting good progress achieved and the overall design is working. However, damage to diodes resulted in a significant setback.
Milt described a 2-micron TmYLuAG PO for a space-based coherent DWL that is being developed for the USAF. CTI is also collaborating with Honeywell and United AL to develop the next generation CAT sensor. A breadboard for this device is ready to be made operational. However, Honeywell and United are now short on funding, so CTI is seeking new partners to demonstrate and continue. Milt noted that CTI can not complete this work without a partner having avionics expertise.
CTI continues to support detection of wake vortices for several airports. Hong Kong, Denver, Dallas, Norfolk, San Francisco have all been served or will be shortly by CTI systems, even though these are still prototypes. Hong Kong will be the first airport to permanently establish a wake vortex detection system. Finally, he discussed airborne systems being studied for the IPO and the NASA aviation safety program.
Dennis Killinger presented a talk on multi-detector processing of vibration-influenced Doppler Lidar returns. An array of heterodyne detectors is used to recover some of the inherent SNR lost to speckle, etc. Dennis has compared several implementations: direct detection with a single detector, heterodyne with one heterodyne with several, and heterodyne using coherent and incoherent summation. He has done this for vibrating and non-vibrating rotating targets. He found that coherent summation is helpful for diffuse targets with spectral broadening whether due to wobble or other source. However, it does not help with specular targets.
Rod Frehlich questioned whether it would be practical to coherently average from space, with low SNR. Dennis acknowledged that this would be difficult.
Bob Otto commented that these investigations should be done as a function of SNR. Dennis agreed with this suggestion, noting that work so far has concentrated on the nature of the noise rather than the level.
Jay Yu (LaRC) reported on development of a double-pulsed 2-micron laser transmitter for wind measurement. This laser is intended for applications including DIAL as well as DWL. It should provide high laser efficiency (one pump, two output), improved beam quality, and reduced cost. Jay reviewed how Ho:Tm can be used to produce two output pulses from a single pump pulse. He presented several diagrams showing how the double Q-switched amplifier energy output exceeded that for a single Q-S pulse, at all input energies about 6 mJ. Analysis of the double-pulse waveform showed Gaussian pulses ~ 100 microseconds. The relative amplitudes of the two pulses are tunable depending on application.
Jay also discussed a conductively cooled diode pumped 2-micron laser, showing photos of the device. Conductive cooling allowed a simplified laser head, with relatively few water lines needed to carry away residual heat. This laser performed almost as well as a fully water-cooled counterpart when operated at low frequency, but did much worse at 10 Hz. This problem was attributed to the high thermal impedance between the diode laser and the heat sink block. The proposed solution is to change the block and head to anodized aluminum for better thermal conductivity.
Lastly, design and thermal simulation of a full conductively cooled 2-micron laser was presented and discussed. The major problem foreseen is that the thermal gradients are likely to be so strong as to result in large mechanical stress on the laser crystal, resulting in some distortion. Finite element analysis showed the predicted stresses are small enough to be confident that the crystal will not fracture. Thus, Jay and the LaRC group hope to complete fabrication of this laser head in about nine months.
Dennis Killinger recommended that actual measurements be taken to supplement the FEA. He expressed concern that real crystals will have different thermal and mechanical characteristics.
Dave Emmitt asked about sources of diodes. Jay replied this is a risk reduction action to be considered by others in the coherent laser group.
Emmitt also questioned whether there is a real advantage to two pulses for wind sensing, since the application depends on the sensitivity. From that perspective, the key issue is how much energy can be put in a single pulse.
Rod Frehlich (University of Colorado) examined some of the tradeoffs between science data requirements and lidar engineering designs, in essence to support the GTWS concept, but from the engineerís point of view. The focus was on random error and coverage versus engineering. Rod started with the definition of truth and error (as delineated in a recent BAMS article.) Rod identified one critical trade between sampling error and instrument error, is where total random error is required to be constant. Another important trade is between azimuth angles for LOS. Rodís analysis indicates that a lidar will sample ALONG track better if sample points are NOT overlaid, but for CROSS track, separation by as little as 30 km can lead to errors as large 2 m/s.
Jan Paegle commented that data assimilation of LOS measurements will be used by scientists as well as by NWP systems, and that only a few scientists will need the orthogonal components directly sensed by the instrument.
Mike Hardesty noted that in practice, the cross-track component is going to be zonal, and thus larger. Therefore, errors of the magnitude foreseen by Rod for separated cross-track sample spots may not be so significant.
Michael Kavaya (LaRC) described a point design for a space- based coherent wind lidar to meet the NOAA/NASA Draft Science and Operational Data Requirements. For the uninitiated, he explained the GTWS mission and the role of the Science Definition Team (SDT) to provide requirements, and he presented the threshold requirements as the target for his point design. He outlined assumptions for orbit, scanning, lidar, and system and welcomed Working Group input concerning his assumptions.
Michael noted that he is bedeviled by a "Wind Shear Dilemma". While targeting a maximum shear of 15 m/s/km, no statistics of wind shear have been provided by the SDT. He solicits further guidance, specifically non-deterministic shear statistics against which to compare his design. In general, Michael is concerned that non-lidar (like pointing) and wind shear errors will consume most of the margin for coherent DWL.
Michael calculated that 5 J pulses are aimed at a 50% enhanced-beta atmosphere; good winds will be achieved 45% of the time. Assuming 70% enhanced beta, he predicts 5 J will give almost complete profiles, with lowest fraction of occurrence at ~ 5 km. He went on to predict that a coherent DWL could provide winds from the surface to 3 km and above 9 with only 2.5 J. Based on this result, Michael recommends that a hybrid point design be commissioned; for example, one in which a direct detection component would target the range from 3 to 9 k. He also requested that a complete probability density function for beta be specified to enable more refined results for point designs.
Rod Frehlich discussed the performance of coherent Doppler lidar for general space-based conditions when pulse accumulation is used. Threshold signal level is determined by the fraction of "bad" velocity estimates. The trade-space is multi-variable. To circumvent this, Rod used an effective Gaussian signal spectrum model, to reduce the space to four parameters. He considers this valid for weak to moderate signal regimes, over which simple scaling laws hold for threshold levels and LOS velocity error. However, Rod recommends that the full parameter space be investigated in the future. He cautions that the full spatial velocity and backscatter statistics over the measurement plane need to be specified.
Rex Fleming (UCAR) explained the role that Doppler wind lidars could play as part of a mesoscale upper air observing system to help mitigate the effects of terrorism. He recalled his standing interest in achieving commercial aircraft wind, temperature, and humidity on an operational basis. The events of September 11 have heightened concern about nuclear, chemical, and biological terrorism. All involve contaminated plumes that must be detected and predicted if lives are to be saved and ënormalí activities resumed later. Satellite data will be too coarse and inaccurate. Hence, aircraft: the data should be accurate, numerous, frequent, and wind errors decrease for shorter forecasts. Formally, he focused on major jets, Rex proposes equipping 2400 planes within three years, for which 20 profiles/day/plane could be obtained. Rex wants to include all nighttime baggage carriers, most regional, and some majors. He would like future instrumentation to include DWL, DIAL, and an interferometer (to determine temperature). Ultimately, he wants to extend coverage over oceans, support both mitigation of the effects of terrorism, and enhance military anti-terrorist activities in other countries. Towards these ends Rex seeks to cooperate with other members of the Working Group, to prepare a proposal to NASA, FAA, and perhaps NOAA.
Tom Wilkerson commented that modeling of this type could help limit over evacuation in the event of an emergency, thus reducing related hazards.
Matt McGill (NASA/GSFC) reported on the results of simulation activities conducted for UCAR and NOAA/ETL. These are small-scale simulations designed to understand better space-based direct detection DWL (355 nm fringe imaging systems) and the impacts of cloud variability. He is seeking to determine what degree of representativeness from various scan patterns and a realistic instrument model can be achieved. He reviewed development of a realistic, small-scale atmosphere based on aircraft flight data. The target atmosphere featured a warm front followed by a cold front. Matt has degraded the aircraft data to simulate sampling from space. He has not nailed down the instrument parameters yet, and so has not predicted the number of photons at each location or the resulting wind error. W. Skinner is to apply photon recycling for the simulated instrument. Mattís team will generate performance simulations for instrument configurations, and will quantify the simulated performance of fiber optic recirculator. They will continue validating the ETL instrument model. This will be completed in the next month and results presented at the summer Working Group meeting.
Mike Hardesty (NOAA/ETL) made a status report on the Regional DWL OSSEs on behalf of his NOAA/FSL colleagues. He noted that these are complementary to the NCEP global OSSEs. For this effort ETL is providing lidar and atmospheric simulations, FSL is generating the regional nature run and providing the Data Assimilation and Assessment, and NCEP has produced the Background fields from the global nature run to set boundary conditions for the regional fields. Mike showed how well FSLís regional nature run matched NCEPís, even by the end of the OSSE period. With confidence from this result, FSL has simulated surface, ACARS, and wind profiler observations, of which Mike showed examples. Initial DWL experiments will be idealized - all lidar LOS measurements will be of high accuracy to establish an upper bound. Later experiments will consider less ideal systems and data. Mike reviewed the validation procedures, and listed on-going issues, in particular, the inherent low resolution of the global nature run, and concerns about the nature run clouds and climatology.
In summary, the regional nature run is complete, conventional observations are being prepared, data assimilation experiments are underway, and first results are expected within a month.
Matt McGill discussed progress in using a holographic fringe imaging system. The key technology is a holographic optic that functions as a circle- to- point converter to measure output of a Fabry Perot interferometer. Matt and his colleagues have assembled a system (532 nm) with a 16-channel array. They anticipate a shift per channel of 83 m/s and are curious to see whether they can resolve 1 m/s motions. Since assembly, the instrument has been used to measure a backscatter profile, which Matt showed. Next steps are to install a scan mirror, and new data electronics are being acquired. Matt is looking for a new detector using photon-counting arrays. Holographic etalons are being considered. When up and running, the instrument will be validated using GLOW.
Wayman Baker gave an NCEP global OSSE status report. He directed the audience to the OSSE homepage, and discussed OSSEs as part of the mission of the new Joint Center for Satellite Data Assimilation (JCSDA.) Wayman stressed the objectives and benefits of OSSEs: impacting instrument design, and optimizing the use of data when instruments come on- line. He reviewed the particulars of the nature run, the NCEP global data assimilation system and the simulation of the observations.
Wayman presented impact results for scanning and non-scanning configurations, for both distributed and clustered shots. Distributed shots with scanning gave the greatest overall anomaly correlation improvement, closely followed by scanning with clustered shots. Non-scanning did not do as well, with little to distinguish the clustered and distributed, at least in composite statistics. For the SH, scanning DWL observations provided noticeable impact whether or not there was clustering. Scanning with distributed shots also did better in the tropics, both at 850 mb and 200 mb.
The need to use alternative metrics to gain greater insight from the OSSEs was addressed. New metrics to be considered include: Anomaly correlation by scale and wave number; jet and cyclone diagnostics; identification and forecasting of extreme weather events; data rejection statistics; and perhaps cost-benefit analyses.
The presentation concluded with plans for new work: additional calibration experiments; the impact of DWL observations with cloud drift winds, more realistic error assignments, and adaptive targeting. More OSSEs are to be performed for other future instruments. These studies will use more current simulated observations, and will be done with an upgraded assimilation system and a correction for an SST bias. Instruments to be tested include AIRS, CrIS, CMIS, and the ATMS.
Dave Bowdle (University of Alabama in Huntsville - UAH) presented simulations of backscatter and velocity measurements from river surfaces using the NASA/MSFC pulsed 2-micron Doppler lidar, which is being investigated as a non-contact means of measurement for stream flow. Dave discussed the lidar and scanner, and indicated that the long-term objectives are to complement radar stream flow observations and to help relate velocity with bottom topography and discharge.
The accuracy and quality depend on several factors: wavelength (2 microns is not ideal), surface roughness, incidence angle, turbidity, surfactants, and depth of penetration.
The lidar now being used is capable of measuring the near surface wind velocity. For a hard wet target (a water slide) at MSFC, preliminary results are encouraging. The system can see water flow down, and the decrease in velocity can be noted as the feeding tank slowly emptied, while also detecting zero velocity when the beam hits portions of the stationary Plexiglas surface. For a dry target, the system has achieved 0.1 m/s standard deviation about a mean of zero.
Dave reported that surface tension effects caused problems, comparable to what might be encountered on a real active river or the ocean. There are plans to investigate more conditions, for example, with sanded Plexiglas, as soon as the lidar is repaired. Dave intends to vary flow thickness and velocity, and add wave perturbations.
Asked about the thickness of the flowing water, Dave indicated that the cases so far had depths of 0.5 mm to perhaps several mm.
Dave Emmitt pointed out that this work is related to the Twin Otter Doppler lidar, and is expected to give a good laboratory baseline for reflectivity (and velocity discrimination) as a function of incidence angle for the TODWL work.
Bruce Gentry (NASA/GSFC) discussed technology assessment activities in support of the GTWS. He cautioned that he is not putting out a point design as such. However, for the GTWS Technical Assessment Team he has begun to consider the ability of direct detection lidar (DDL) to address the draft requirements. Bruce considered a generic DDL design, and is open to new technologies that might become available. The generic design is based on a common lidar model developed by Matt McGill and used successfully by NOAA and UCAR and the target atmosphere that is in the draft requirements documents.
Reviewing the interaction of the atmosphere and direct detection systems, Bruce noted that the benefit of including an aerosol channel is manifest only at low heights, only when aerosols are enhanced, and only with a big increase in power aperture product relative to the direct detection lidar molecular baseline. Wayman Baker asked whether this argues for the direct/coherent hybrid. Bruce agreed that would be a reasonable interpretation.
The requirement for eight lines of sight is challenging a generic direct detection lidar, and pushes the design to a large power-aperture product. Bruce summarized the direct detection technology tall poles as follows: lasers, telescopes, scanning optics, and detectors (high quantum efficiency, and low noise), both single elements and arrays.
Rex Fleming argued that the requirements are far too severe. Jim Yoe and Dave Emmitt defended the position of the Science Definition Team that the requirements reflect a data product that will bring demonstrable science and operational capability, and noted that the requirements had been relaxed when quantitative justification to do so was available.
Dave Emmitt reported on the Twin Otter Doppler Wind Lidar (TODWL) and other IPO funded activities. Imminently scheduled field experiments with TODWL will target ocean surfaces with Doppler lidar. TODWL will measure reflection as a function of incidence angle, sea-state, etc. A major goal is to learn how to discriminate between near surface aerosol and the underlying surface. Dave pointed out that as many as five distinct types of motion are likely to occur in the lowest range gate. He also plans to look at atmospheric PBL roll circulations. Finally, he intends to evaluate TODWL using "comparisons of opportunity" (COOs).
Dave briefly reviewed technical features of the instrument (refer to previous minutes for details). The TODWL team planned to accumulate about 25 hours of total flight from Feb 10-15, 2002 near Monterrey, CA and to fly low and slow to ensure surface signal at multiple incidence angles.
Dropsondes will be used for intercomparison as well as COOs. The drop system was installed and was scheduled for check out during the last week of January 2002.
After the Monterrey experiment, the lidar will be shipped to CTI, where it will be installed in a trailer, and then sent back to Charlottesville. It will be available for use in other missions (with Goddard Lidar Observatory for Winds (GLOW) for example.)
Next Dave discussed his IPO-funded effort on the NCEP OSSEs. The impact assessment of simulated DWL bracketing is now yielding results (as evidenced by Wayman Bakerís earlier talk.) Dave now has also simulated cloud track winds (CTW), which need to be added for a more realistic control in future OSSEs. The University of Wisconsinís CTW group has evaluated and approved the simulated CTWs. All of the Simpson Weather Associates simulated products will also be used in the new NASA/DAO OSSEs.
Dave also discussed the "rapid response" OSSEs (RROSSEs) undertaken for the GTWS requirements development. These make use of the same data assimilation front end as the full OSSE, but for simplified, prescribed flow features. RROSSEs have been applied to address the need for bi-perspective sampling and the effect of angle between two looks in framing GTWS requirements. Dave is currently working a RROSSE to explore the trade between accuracy and representativeness. Dave invited suggestions for additional issues to be addressed by RROSSEs, noting that they can be run overnight. Dave concluded by discussing plans to investigate adaptive targeting of DWL observations via numerical experiments in collaboration with Zoltan Toth and Eugenia Kalnay. He acknowledged that turning lasers on and off might be too risky for a space-based DWL, but he hopes and expects that the possibility of programmable scanning will be left open to permit adaptive targeting.
Bruce Gentry asked whether a RROSSE could address the relative merit of cross-track measurements. Dave affirmed that it would be a suitable issue to explore.
Bob Brown asked Dave to elaborate on biases in CTW observations. Dave explained that the assumption of winds moving with clouds might be invalid on occasion, for example, if the wind moves through standing orographic waves.
Dave Emmitt proceeded to present an instrument concept for a hybrid DWL, drawing on work dating back to a 1995 proposal. The intent is to capitalize on both direct and coherent detection strengths, and thus mitigate the need for very large lasers. Perhaps they could also share the cost of platform, pointing control, mission management, and science team. Dave hopes to use coherent and direct decection lidar point designs to help formulate a hybrid point design. The IPO has provided funding for a hybrid DWL OSSE, to be run during the spring of 2002. When the OSSE is complete and lessons gleaned from it, Gary Spiers and JPL will do a point design for the hybrid DWL.
Dave emphasized the prospects for scientific synergy via the hybrid. For example, the coherent system might target ageostrophic features in the lower troposphere, while the direct detection system portion could be optimized to investigate divergent features in the mid-and-upper troposphere. He also stressed that there will be competing Observing Systems - ACARS, sondes, CTWs, scatterometers ‚ that will drive any DWL to get the most value and impact from its finite resources.
Steve Mango (Integrated Program Office-IPO) gave a status update for NPOESS, noting a lot of progress in the last six months. He stressed the partnership of the JCSDA to speed the numerical experiments and reduce the per agency cost. Overall the NPOESS program itself is on course, despite a narrowly avoided budget snag, as some cost-plus contracts begin to ramp up to tackle the hardest development issues.
The IPO is looking forward to launch of NASA ës AQUA in mission in 2002 and the lessons its sensors will provide for NPOESS. Also, the NASA Preparatory program will carry three payloads for NPOESS risk reduction in 2006. These missions and plans for NPOESS itself are all progressing well. Steve pointed out that the biggest uncertainties on the launch schedules are associated with the abundant POES and DMSP satellites yet waiting in the queue.
Steveís perspective on "which way the wind is blowing?" is that NOAA, NASA, the IPO, and international communities are all in different positions. He believes that a convergence of efforts is critical, and commented how successful this approach had been for NOAA and DOD in converging the polar satellite programs.
NPOESS requirements are evolving and increasing in number as a consequence of the pre-planned Product improvement (PPPI) process. New requirements for aerosol and cloud parameters have led to a new instrument (polarimeter.) The second version IORD, validated in January 2002, contains 22 unmet EDRs as compared to just nine in IORD I. Winds are still foremost among these. Steve regards the situation as generally positive. Remarking that aerosols pose the largest uncertainty in climate forcing, he asked whether lidar and wind data could help characterize aerosol concentration and transport to address this issue. If evolving requirements and capability warrant, the U.S. NPOESS Lite mission may offer a platform for DWL. Steve noted that WindSat Coriolis is moving forward. NRL has delivered the payload to the integrator. Launch is hoped for next Fall as a proof-of-concept mission.
Dave Emmitt asked whether opportunities exist before NPOESS Lite, and whether such a DWL would have to be fully operational. Steve replied that there could be an opportunity as early as a 2009 launch, although he thought that would be tight for instrument readiness. He indicated that not every instrument flown needs to meet operational requirements.
Dave Bowdle asked whether Homeland Defense considerations are likely to impact the priorities or schedule of NPOESS. Steve said no. Milt Huffaker wanted to know if the IPO has a plan to get tropospheric winds. Steve pointed out that winds are not mandated as such for the POES and DMSP convergence. Therefore, the community has to work the angles of requirements and readiness, which is one reason the IPO has had to limit the resources brought to bear. The prospect of a wind data buy mission has also had an impact, rendering it inappropriate for the IPO to formulate, let alone execute, such a plan.
Navy Lt. Commander Dan Harrison discussed the DoD requirement for global wind profile observations, and thanked John Pereira and Wayman Baker for soliciting DoD participation. Dan mentioned that he has a meteorological background, and has worked with lidar on ships for moisture and temperature sounding in the past. Dan circulated the GTWS draft data specification within the Navy and received feedback that the operational requirements are different from those of NASA and NOAA. For example, for time critical targeting, 2.75-h reporting is not good enough. Also, the Navy might require 0.1-km vertical reporting interval. Some are concerned about features missing in the reference design atmosphere, such as marine inversions, etc.
The immediate DoD perspective is driven by events in the Middle East. The most pressing goal is to extend reliable imaging to relevant portions of the globe not covered yet. In the longer term Dan would like to see an overarching requirements document for the DoD requirements. He acknowledged the DoD input to the IORD and PPPI for their global needs; DoD also has more stringent tactical requirements.
Michael Kavaya cautioned that the GTWS requirements are predicated on the assumption of DWL, and that they were driven largely by NWP. He argues that instrumentalists need complete specifications and advises DoD to take care not to cast single, incomplete specifications.
Steve Mango commented that the IPO has included Navy insight to help set requirements via the Oceanographer of the Navy, along with USAF and Army requirements.
Rex Fleming reiterated the perspective has changed since September 11. Battles may be fought at home, and all requirements and programs, including NPOESS, need to be examined afresh.
Michael Kavaya spoke on a new NASA Technology Development Program for risk reduction of space-based lidar missions. Cost and schedule overruns associated with previous lidar missions compelled NASA to convene an independent laser review panel, which recommended that technology should be mature before a science mission is approved. Ghassan Asrar directed LaRC to implement an Integrated NASA Lidar System Technology Team, which has compiled a report on all NASA programs that (could) benefit from lidar. Six priority Earth Science measurements including winds were identified. The LaRC team noted that all of this could be done with essentially two lasers, and recommended that test beds be established to develop these laser technologies. They also urged that appropriate efforts be made to ensure that suppliers of laser diodes do not disappear, and space hardening of diodes is supported.
Michael mentioned that a proposal was made to the White House for a five-year, $70 M Advanced Active Instrument Technology plan that incorporates this work among others. Some internal NASA money is being spent in FY 02 until the fate of this proposal is known. This includes beginning 2-micron laser risk reduction. Some work on diodes and frequency transition to UV is planned, and some attention is focused on CO2.
Detector development for DIAL, and receiver/detector development for DWL are both needed. Most of these planned activities are not funded, but the structure has LaRC prepared to respond to announcements of opportunity.
Gary Spiers asked Michael to clarify whether the proposal included just an NASA Earth Science Enterprise (ESE) lidar, or all of NASA? Michael indicated ALL science. Gary commented that 1.3 and 1.5 micron have been chosen by many of NASAís space scientists, and wondered whether the development of 2 micron (and its harmonics) would be of significance to them.
Carl Nardell asked whether 2 micron and 1 micron factor equally in the plan. Michael and Frank Peri replied yes, both in terms of resources and intended science benefit.
Geary Schwemmer (NASA/GSFC) presented the first of several talks on new simultaneous GLOW and (HARLIE) wind measurements, an effort dubbed HARGLO-2 and supported by NASA and the IPO. Objectives of the campaign were to get intensive intercomparisons of these two (and other) instruments, including balloons and scanning radar. The statistics for overlapping wind measurements are sought to help develop calibration and validation capability for any future space-based wind sensor, and to develop techniques to generate integrated wind profiles using the best parts from the complementary systems. Geary noted that collaborators at Utah State University combined images from a cloud-tracking camera and cloud height inferred from GLOW to produce cloud track winds for portions of the campaign.
Geary reviewed how HARLIE is scanned to track aerosol structures whose motion is used to infer wind profiles. GLOW is the van-based double-edge filter DWL optimized for clear-air (molecular) scattering. Both employ 90-degree conical scanning during the HARGLO-2 campaign, conducted at Wallops in November 13-20 2001. They were able to amass four good days of intensive measurements, concentrating on sunrise and sunset, to investigate wind variations expected near the coast. In addition, they tried to operate HARLIE in a 24 h, nearly turnkey mode.
All campaign data were available to all parties, and comparisons between level one data were made by all, no blind intercomparisons were being tried at this point. Level 3 data were produced as horizontal wind vectors with 30-minute averaging at 200-m altitude intervals. All data were reported in standardized ASCII files, and all included some type of error bars. The team is just beginning cross comparisons, and only preliminary samples are prepared for this meeting. More complete statistics will be presented in the summer.
Dave Miller reviewed the synoptic context of the HARGLO-2 campaign, making use of satellite imagery to illustrate the range of conditions at and around Wallops. He pointed out that one of the goals of the experiment was to determine some of the conditions for which successful simultaneous operation of GLOW and HARLIE might be expected. A summary of the campaign observations indicates skycam data during daylight, intermittent radiosondes, nearly continuous HARLIE, and intermittent GLOW operation. Dave then give a day-by-day synoptic summary description. There were consistent sensor, radiosonde, and satellite feature identification of fronts and clouds, for example.
Tom Wilkerson (Utah State University) elaborated on the various means of extracting winds from HARLIE data. He is doing this work with undergraduates, continually refining the techniques first presented at Oxnard in 2001, with the goal of developing a mature operational capability for HARLIE as a cal/val sensor. Tom reviewed conical scanning and curve fitting, noting that video imagery, automated pattern recognition and tracking, and automated data reduction for HARLIE have advanced significantly in the past year. The phase-amplitude fit for obtaining wind speed and direction has been automated. Tom has been able to derive velocities to altitudes as great as 1800 m with speeds of 8 m/s. They have also tried a process called "block-matching" of cloud tracking, using an optimum fit between successive images, to which gradient analysis is automatically applied.
In general, automated reduction (of HARLIE) works, as does automated cloud tracking. Tom cautioned that sometimes the automatic and manual (interactive) wind values for the same HARLIE data do not match well. This is an area of on-going investigation. Preliminary intercomparisons between HARLIE (manual extraction) and GLOW have been made. Tom plans to complete reduction and comparison of the data using correlation and Fourier analysis. New campaigns are also being considered.
Bruce Gentry reported on results and prospects of the GLOW and HARLIE winds. To facilitate this comparison it was necessary to lower the GLOW coverage, which was accomplished by reducing GLOWís transmitting power. Normally GLOW sacrifices the boundary layer because in high-energy mode the detectors are gated off to avoid saturation. When power is reduced to permit low-level sampling, coverage in upper gates is lost by virtue of the reduced number of photons.
GLOW data were obtained at the four cardinal compass points with 45-degree elevation, and LOS velocities calculated as functions of height. Error bars presented indicated standard deviation of the mean, or simply the shot-noise limited estimate from the photo-count, which was much smaller, since standard deviations contain sampling as error as well. However, the cases are sometimes such that the two error estimates are similar. The shot-noise is the idealized instrumental error. In summary, Bruce has the data-gridding completed and preliminary intercomparisons indicate good agreement between the one-sigma winds. Bruce is looking forward to HARGLO-3 and other campaigns.
Dave Emmitt asked whether any surprises at the cloud boundaries have been noticed. Bruce replied no, that they observe the non-linear biases that they expected, in that thin cirrus presented no problems, but thicker low-level clouds simply blocked the signal.
Geary Schwemmer summarized plans for HARGLO-2 analysis. With a total of six instruments and six observing days ‚ 4 of which can be considered prime ‚ the team plans to present statistics by the next Working Group meeting and to submit papers within a year after the experiment date. They would like the next campaign to add a heterodyne DWL, and to incorporate airborne measurements to extend the development of space-based cal/val, and to provide a means to "tie together" the ground sites. Geary indicated that they would like to conduct HARGLO-3 in the mid-west or on the west coast. In the longer term, there are plans to integrate the HARLIE and GLOW technologies.
Wayman Baker provided an update on the Winter Reconnaissance Program (WRP) on behalf of Zoltan Toth (NCEP). The WRP is in essence an Adaptive Targeting (AT) exercise using dropsondes. From a menu of pre-programmed flight tracks, an NCEP Senior Duty Meteorologist chooses when and where to fly and sample. Summary statistics show that the dropsondes have a tendency to reduce wind vector errors in the forecasts, in 70-90% of cases over all field programs. The targeted forecasts gained 12-24 h lead-time. An average 10-20% error reduction in the verification error has been found. Thus, overall AT is showing encouraging capability. Despite previous improvement attributed to ACARS, the small number of dropsondes in the WRP data set reduces the upstream uncertainty enough to have a statistically significant result.
Dave Emmitt asked if wind and temperature impacts and high/low impact results have been partitioned. Wayman replied not yet, but confirmed that there are plans to do so.
Jan Paegle wanted to know how long the WRP will continue. Wayman said there is continued operational support. Jan remarked that the WRP cost could be such as to make an argument for space-based lidar.
Mike Hardesty asked what aircrafts are used. Wayman responded the USAF C-130 and the NOAA G-4.
Jim Yoe (NOAA/NESDIS) spoke for John Pereira on the Global Wind Demonstration Project, which encompasses activities related to the joint NASA/NOAA GTWS collaboration as well as NOAA/NESDISí work with the GroundWinds technology development effort.
The University of New Hampshire (UNH) is overseeing installation and integration of a second GroundWinds lidar in Hawaii. It was noted that subsequent presentations would describe this instrument in more detail, including how it has been designed to incorporate lessons learned from the original New Hampshire GroundWinds instrument. The anticipated role of GroundWinds Hawaii to improve weather forecasts to support the program of astronomical observations atop Mauna Kea was described. Key events coming up for GroundWinds include a quarterly review in Hawaii in March 2002, simple system upgrades and new science measurement campaigns in New Hampshire, and the July 2002 Working Group meeting in North Conway, NH. In summary, the GroundWinds project is helping to identify and understand some of the technical challenges associated with DWL.
The GTWS work has resulted in the development and release of the draft data requirements, and the receipt of community feedback on these requirements. In addition, NASA has conducted concept studies for both direct and coherent detection space-based lidars to address the threshold requirements. The requirements and concepts are considered useful reference points for continued pursuit of a GTWS mission. Detailed consideration of these topics was deferred to later presentations.
Frank Peri (NASA Earth Science Technology Office - ESTO) discussed the development of an integrated ESE lidar strategy, remarking that the thrust of NASA lidar science is motivated by Earth science needs. ESTO has noted GSFC and LaRC are cooperating to formulate a joint lidar plan and to ensure lidar technology is tested, as well as the recommendations of the independent lidar review panel. The ESTO strategy is to build on these ideas, recommendations, and activities, by defining and pursuing key tasks to develop: laser transmitters for two fundamental wavelengths, laser diodes to enable transmitters, and efficient wavelength transition technology for each fundamental wavelength.
The laser transmitter task is funded at $1.1 M in FY2002. Deliverables expected for the year are diode lasers, thermal and optical simulation of the laser head, knowledge of bonding procedure, and a seed source with better than 50% efficiency. The task for laser diode array is to work with industry to ensure development and supply. In FY2002, $ 1.4 M is assigned to develop requirements and perform initial selection, testing, and analyses. Two classes (one for each fundamental wavelength) lead to shared oversight responsibility for Goddard and Langley. The wavelength conversion task ($1.5 M) is to focus on the ND-YAG.
Frank maintains that key lidar technologies are not mature enough for space-based instruments, and that the community believes NASA must invest in: laser transmitters, receivers, scanners, and detectors. He recognizes that the current ESTO investments are insufficient, but if a data buy is no longer the only possible solution for global winds, it is appropriate to consider a technology development and risk reduction effort on the government side.
One strategy that might be pursued is to develop a straw man plan, perhaps for a hybrid DWL. Ideally, the straw man could be sufficiently advanced to support a request to OMB for FY 04 funds to support a formal formulation activity for a space-based wind measurement program. Frank proceeded to show a Hybrid Wind Lidar Technology plan as recently presented to Ghassem Asrar. He said that the logical next step is an aircraft demonstration, directed towards validation for a space-based demo. This approach would still be open to data buy, but provide a path for NASA to do some of the important technology-enabling work. Frank thought this was well received. He would like to get all players ‚ NASA, NOAA, IPO, and DoD on board and figure out how to fund it.
Wayman Baker complimented Frank for NASAís planning. He added that it has been a long struggle to achieve a critical mass of partners to make the case for an operational wind mission sufficiently compelling.
Mike Hardesty remarked that Frank discussed laser specs a great deal, and wondered how we decide what is a point design target for this activity. Frank replied that a hybrid is promising, given current state-of-the-art and likely investments. Mike cautioned that Frankís schedule seems ambitious. To stay on it really requires an operational specification to target, otherwise, the likely outcome will be a design tailored to the money available.
Dave Emmitt asked Frank if he has thoughts on how the DoD can bring $ or other resources to the table. Frank replied that he has no specific means identified.
Steve Mango commented that Frankís presentation amounts to setting a foundation for a partnership. The IPOís perspective is that partnerships are essential ‚ so much so, that we should not wait for the R&D community to come to us, but go out and engage-finance them.
Dave Emmitt discussed the GTWS Target Reference Atmospheres and their uses. He explained that they are intended to stimulate discussion and facilitate rough calculations ‚ but NOT to be taken as absolute truth. For example, he explained that the thinking behind the reference jet stream is not to accurately reflect the strongest or most typical jet, but simply to enable someone to examine how a system might deal with a particular shear.
Finally, Dave emphasized that considerable caution should be exercised with respect to the scaling of values based on measurements taken at one wavelength to approximate what might be found at a different one when making calculations based on this or any reference atmosphere.
Bruce Gentry asked whether nature runs for OSSEs are being updated in accordance with refinements being made to the reference atmospheres. Dave confirmed that they are, and mentioned that Sid Wood would at least touch on this in a later presentation. He elaborated that OSSEs have a problem with clouds (adjustment needed) and aerosols (simply absent) in the nature run. Hence, the bracketing in the background and enhanced modes. Real systems will need real aerosol distributions, even though water vapor may be conveniently used as a proxy.
Rod Frehlich urged that an improved sub-grid turbulence factor (other than sigma) be incorporated in the reference atmosphere.
Ken Miller (Mitretek) discussed the GTWS Reference Designs from the NASA Instrument Synthesis and Analysis Lab (ISAL) and Integrated Mission Design Center (IMDC) activities, remarking on the coordination of many people and organizations (the GTWS SDT and Technical Assessment Team (TAT) as well as Goddardís ISAL and IMDC teams.) Ken emphasized that the purpose of developing these designs for space-deployed sensors/missions is to provide to the government reference points by which to evaluate actual concepts later, to identify and illustrate tall poles for readiness and risk, and to support government cost estimates and sanity check. There is no assumption that these rapid response designs will resemble what actually ever flies.
The ISAL teams developed the rapid designs with assistance from the TAT representatives, and with explanation and clarification of the threshold requirements from the SDT. Ken pointed out that certain threshold requirements ignored, for example, mission lifetime, and the fact that a single satellite might not meet the coverage requirement. He cautioned that in the spirit of providing reference points, exhaustive technical trade studies were NOT made, for either the coherent or direct detection designs. Limitations exposed by the ISAL/IMDC exercises center around the low technological readiness of many significant components, as alluded to by Frank Peri. Ken did not provide numerical figures, which must be regarded as competition sensitive until the agencies are directed otherwise. But he summarized qualitative characteristics, noting that both designs pointed to large, power-hungry systems that drive mission costs up. Some specific drivers included assuring battery power. A conventional launch vehicle should have lift to spare, but not much space, at least for one of the designs. Ken mentioned that controlled disposal requirements might add some cost not currently considered.
In conclusion, there is a need to increase the technology readiness level of the lidar components, and to reduce the weight, power, and size and size requirements. Ken pointed out that some of the challenges might be addressed by re-considering (relaxing) the requirements if that can be justified. Finally, he identified risks in scanner, lag-angle compensation, solar backscatter suppression, and pointing and jitter from the spacecraft.
Wayman Baker asked whether a hybrid point design is in the works. Ken replied that NASA/JPL is taking the lead on this. Gary Spiers noted that JPL is working on it jointly with GSFC and LaRC.
Steve Mango wanted to know if alternatives to the Delta rocket with a 10 ft fairing have been considered. Ken confirmed that a smaller option was sought, but none was found that would support a mission. Steve expressed concern that the Delta represented a formidable cost driver for a first mission.
Gary Spiers asked whether the point designs included a cost estimate? Ken replied that cost was only considered informally, after the fact, not as a constraint.
M.K. Rama Varma Raja (CIRA) and Jim Yoe presented some updated comparisons of wind observations from the GroundWinds Demonstration Campaign of September 2000. Doppler LOS retrievals for the two direct detection DWLs had been re-processed after preliminary results were analyzed. Original GLOW (the Goddard Lidar Observatory for Winds) processing used climatological temperature profiles to account for the thermal distortion of the spectral shape of the echoes reaching the edge filter (Doppler shift ) detectors. Reprocessed retrievals were made using temperature profiles from the locally launched radiosonde data. For GroundWinds, the aerosol and molecular channel retrievals were de-coupled in the reprocessing. For the final day of the campaign extended observations were made with both direct detection DWLs with multiple radiosonde launches made at frequent intervals to validate the temporal evolution of the wind field and cloud cover. Reasonable agreement was found for the ten-minute averaged LOS winds when returned signals were sufficiently strong; typically to about 11 km for GroundWinds and 14 or 15 km for GLOW. Both direct detection instruments were adversely affected by the presence of clouds.
Rama Varma Raja presented results showing the capability of GroundWinds to detect and track aerosol layers. Time-height sections of the GroundWinds aerosol-molecular ratio (number of aerosol photons divided by the total number of photons) show not only the aerosol-enriched boundary layer but also the evolution of cloud layers. Vertical profiles of relative humidity from radiosondes and eta model analysis typically feature corresponding enhancements at the same altitudes.
Phil Dunphy (University of New Hampshire) provided a status update for GroundWinds, NH. He enumerated recent improvements to the facility. The Mount Washington Observatory has a new building on the premises which can serve as an office for visiting scientists. The parking lot has been paved, eliminating a source of dust that was a threat to the telescope. A new, sturdier telescope dome and more stable telescope mounts have been installed as well.
Phil presented some of John McHughís results of GroundWinds velocity spectra, which are being explored as a means to measure atmospheric turbulence. John McHugh plans more extensive campaigns to investigate turbulence, gravity waves, and to map flow features over Mt. Washington. Comments were made regarding the care that must be exercised in trying to infer turbulence.
Other topics of investigation that have been attempted or are planned for GroundWinds NH include, examination of fluid effects on the laser beam, detection of dust plumes generated over Asia, and measuring the lidar de-polarization. UNH aims to have GroundWinds evolve to an operational status, meaning 50% operational time ‚ 3 days/week, 12 h/day. Those interested in using GroundWinds NH for research projects were encouraged to contact Ivan Dors of UNH.
Dave Bowdle asked about the capability to vary the elevation of GroundWinds to angles other than 45 degrees. Phil replied that the elevation remains fixed, and that the FAA regulations restrict the choice of azimuth somewhat, too. Bowdle commented that the single elevation limits the practicality of some aspects of the proposed science.
Carl Nardell (Michigan Aerospace Corporation ‚ MAC) presented plans for GroundWinds Hawaii. The facility at Mauna Loa was shown; it is complete and components of the system are being installed. Carl discussed how various components have been redesigned for GroundWinds Hawaii. Some are intended to render the instrument a more realistic model for a space-based instrument (UV laser and more compact optical train.) Others incorporate lessons gleaned from building GroundWinds NH (improved control system interface, higher quality etalons and interferometers, improved thermal stability (alleviating the need to correct for drifting zero), and a patch panel to facilitate programmable photon recycling configurations.) Carl pointed to related work undertaken by MAC, including the etalon design developed for PICASSO/CENA. For the future an appealing concept might be a low cost science mission to demonstrate a fringe imaging DWL "for space". Carl argued that the best corresponding fit and function could be a balloon mission. He noted that a high altitude balloon presents the comparatively small dynamic range as well as "point down" geometry that would be encountered from space. He indicated that MAC wants to build the laser for the balloon mission in collaboration with another firm, and will continue to support the NH and Hawaii instruments.
Other future activities include upgrading components of the GroundWinds NH instrument. MAC is also investigating linear array detectors as an alternative to the streaking CCD approach used so far.
Carl also showed GW NH data; profiles, noted STD dev as function of photons.
Bob Brown ‚balloon wonderfully ambitious but how will they get collocated data for validation? Carl acknowledged that the balloon canít be steered.
Dave Bowdle reviewed the concept and status for the Regional Atmospheric Profiling Center for Discovery (RAPCD) at UAHís Global Hydrology and Climate Center. A new lab facility is being developed at Huntsville, for aerosol and gas detection (simultaneous). Associated mobile instrumentation included a SODAR, a ceiliometer, and a 915 MHz Doppler radar. In addition, the area offers several NWS Doppler radars and an Army installation with radar and routine ozonesonde launches. Discussions with GSFC may lead to the use of a DIAL system for aerosol and ozone monitoring. In short, the facility is to be world class and ready for operation by July 2002.
Rod Frehlich asked Dave if RAPCD might produce statistics on the correlation between backscatter and wind. Dave replied that he hopes to be able to do this using multiple instruments.
Gary Spiers (NASA/JPL) reported on JPLís Laser Remote Sensing Groupís activities. A re-organization has placed this group within a larger optics and interferometry section, which they hope to be able to use as a stage for lidar development activity. Gary discussed major projects within this section, many of which are associated with space science as opposed to Earth science. Among these are a laser absorption spectrometer (a CW DIAL variant), the LAMP instrument for Mars, a COTS lab bench instrument ultimately intended to measure Martian winds (dust devils, etc.) There is also a 2-micron diode LO development program, and the hybrid DWL point design activity to complement the ISAL/IMDC coherent and direct detection designs.
Gary announced that JPL has opportunities for lidar researchers, engineers, and optical designers.
Sid Wood (Simpson Weather Associates) demonstrated the Operational Doppler Lidar Simulation Model and accessed it by connecting to the SWA website via cable modem. The model has its origins in coherent DWL studies begun in 1995, but has been updated as part of SWAís support for GTWS investigations, and is applicable to any DWL. The intent of this work is to make a reasonable and consistent model available to the entire community, thus facilitating more meaningful intercomparisons. Once a lidar concept is picked, the database of ECMWF and NASA DAO nature runs are in one place for extracting simulated observations. Sid noted, on the other hand, that it is being distributed online rather than by CD-ROM because it is and will be subject to updating; keeping track of the different versions will be a challenge.
Rod Frehlich asked how shear and sub-grid variability will be included in the model. Sid replied that these are not currently available.
Sid was also asked whether the model can reproduce GASP aerosol observations. The reply was that GASP data were used to check the statistical correctness of the database.
Ross Hoffman reported about attempts to define requirements for operational marine forecasting, on which he has collaborated with Rod Frehlich and Paul Chang (NESDIS). The emphasis has been on scatterometer data and extreme wind events. The draft document is similar to that compiled by the SDT for tropospheric winds, but they havenít reached consensus yet. There are some differences for this particular brand of forecasting, however. The main requirement is that data be available to see hurricanes: They must be delivered in less than 2 h, refreshed every 4-6 h (implying either a large swath or multiple platforms) and quality control is very important ‚ more so than accuracy. The resolution should be such as to allow positioning a storm center to within 10 km. Also, in contrast to GTWS, this application is driven by users who want fields of measurements, so that the center can be located, the maximum sustained wind known, and the size (radius) determined. It is not always straightforward to convert a field characterized by several such key parameters into requirements for point measurements.
The minutes were recorded by Dr. Jim Yoe of the NOAA/NESDIS office of Research and Applications.