NEXRAD Now December 2010 Issue 20 Dual Polarization is Coming to NEXRAD! Beginning in 2011, all WSR- functionality. The contractor had the What’s 88Ds will undergo a modification to requirement to implement dual implement dual polarization capabil- polarization on the existing WSR- Inside? ity. This new technology allows the 88D antenna and integrate new func- Page 3 WSR-88D to simultaneously trans- tionality into the Radar Data Acqui- Improving the VWP mit and receive in the horizontal and sition subsystem. The Government Page 6 vertical planes, providing an addi- retained responsibility to ingest new The New Architectured tional dimension of weather features dual polarization data at the Radar WSR-88D Level II Data and giving the weather forecaster Product Generator and make avail- Collection, Distribution, and Archive Network additional and improved tools to able base and derived dual polariza- serve the public. tion products to the forecaster/users. Page 10 ROC Stars Dual Polarization technology has Throughout the program there been the subject of research since the have been two main technical areas Page 11 Information “Tid Bits” 1970’s. However, it was not until of focus: for Improved WSR-88D the Joint Polarization Experiment Sensitivity – Because dual polar- Operations (JPOLE) was conducted by the ization requires splitting of the trans- Page 16 National Severe Storms Laboratory mitted signal into horizontal and What’s Your Question? (NSSL) in 2002-2003 the technology vertical components we expected Page 17 was demonstrated to provide signifi- slight reduction in radar sensitivity. GIS Methods for cant benefits to the forecaster. The Prior to contract award, NSSL stud- Evaluating Wind operational benefits include ied the subject in a WFO setting and Turbine Impacts on improved rainfall estimation, dis- concluded the effect should not be NEXRAD crimination of precipitation types, operationally significant. In March Page 18 Wind Farms and the discrimination between hydromete- of this year, we utilized data from the WSR-88D -- An Update ors and non-hydrometeors, and Dual Polarization prototype in a Page 23 improvement in data quality. Subject Matter Expert review and Integrated Real-Time Based on the results of JPOLE, reached the same conclusion. The Performance Monitoring the National Weather Service Office Operational Assessment conducted of Observing Networks of Science and Technology entered in August with 20 field forecasters in China into a contract with L3 Communica- was consistent with these earlier Page 31 tions/Baron Services in September findings. An Historical Look at 2007 to develop and deploy this new Continued on Page 2 NEXRAD NEXRAD Now Dual Polarization Continued from Page 1 Calibration – It is critical that any bias between ment to follow beta test completion. The installa- the horizontal and vertical channels be accurately tion requires the site be off-line for up to12 days, determined. The contractor has implemented an requiring careful planning to ensure contiguous automated calibration process to periodically sites are available to provide coverage and to avoid check this differential reflectivity (Zdr) bias. The typical periods of adverse weather in the region. contractor and consulting government subject mat- Production installation will begin slowly with ini- ter experts have also spent a great deal of time tially only two teams in the field. We intend to refining the calibration process which must be ramp to five teams as deployment progresses. conducted by the on-site technician (e.g., when Deployment is scheduled to be completed in Janu- certain parts are replaced). ary 2013. Maintenance and operations training are a big We look forward to bringing this important part of the Dual Polarization program. The con- new technology to the WSR-88D for the benefits it tractor conducted a ‘Train-the-Trainer’ session will bring to the public. Please do not hesitate to with the NWS Training Center in support of dual contact our office with questions. Additional polarization maintenance training curriculum information on the project is available at the “Dual development. The intent is to follow the Open Polarization” section of the ROC web site: RDA training model, with the NEXRAD Product http://www.roc.noaa.gov/WSR88D/. Improvement program paying travel costs for two technicians at each site, and at least one technician Greg Cate trained prior to their site being modified. The NEXRAD Product Improvement deployment schedule will drive the training sched- ule, timing the training of the technicians in a time period not so early the training cannot be retained, and not so late there is inadequate time to assimi- late the training. Operations training takes on new criticality, given the addition of even more data available to the forecaster and the complexity of the dual polar- ized data itself. During the last two years, Warn- ing Decision Training Branch staff have been developing distance-learning courses for forecast- ers, as well as outreach material for public and pri- vate users of radar data (e.g., emergency managers). These materials are available at http://www.wdtb.noaa.gov/. Current plans call for beta test to start in Wich- ita, KS in January 2011, with production deploy- page 2 NEXRAD Now Improving the VWP O ne of the most widely used products in the calculate a representative wind estimate for the par- Weather Surveillance Radar – 1988, Doppler ticular height. However, in many meteorological (WSR-88D) product suite is the Velocity Azimuth situations, this is not a valid assumption. Display Wind Profile (VWP) product. The VWP The Enhanced Velocity Azimuth Display Wind product provides a time verses height wind profile Profile (EVWP) function is designed to improve for the volume above the radar location. the availability and accuracy of VWP wind esti- The VWP product uses the wind estimate mates. The concept behind the EVWP function is derived by the Velocity Azimuth Display (VAD) the fact that each VWP height is achieved at differ- algorithm for each desired VWP height. At the ent slant ranges, depending on the elevation. At the beginning of each volume scan, the VAD algorithm beginning of each volume scan, the EVWP func- calculates the elevation/slant range pair for the tion calculates every possible elevation/slant range active Volume Coverage Pattern (VCP) required to pair for the active VCP that achieves a height spec- achieve the heights specified for the VWP product. ified for the VWP product (see Figure 1). As each The VAD algorithm uses a slant range parameter elevation is scanned, the EVWP function passes (default = 30 km) to guide the selection of the ele- these additional slant ranges to the VAD algorithm vation angle for each required height. For any par- to process. The VAD algorithm computes a wind ticular height, the Continued on Page 4 elevation angle with slant range VCP 12 closest to the slant 0.5 0.9 1.3 1.8 2.4 3.1 4 5.1 6.4 8 10 12.5 15.6 19.5 range parameter is 50000 used to compute 45000 the wind. The VAD wind 40000 estimate for each 35000 height is based on 30000 the data from a sin- 25000 gle elevation/slant FT HGT range pair. (For 20000 Clear Air Mode an 15000 average of three 10000 range bins is used.) This assumes that 5000 adequate return is 0 available, using the 10 20 30 40 50 60 70 80 90 100 110 120 KM single elevation/ slant range pair to Figure 1: VCP 12 Elevations Plotted on Range/Height Grid page 3 NEXRAD Now VWP Continued from Page 3 estimate for each height (identified slant range) inter- sected by the ele- vation scan. Each wind estimate is passed to the EVWP function for validation. Using multiple ele- vation/slant range pairs for a given height increases the likelihood of sampling valid returns from which Figure 2: KTLX Reflectivity Products from 22:30Z and 23:20Z to derive a repre- sentative wind estimate for that height. At the end “best” wind estimates are used to build the final of the volume scan, the EVWP function selects VWP product. the “best” VAD estimate for each height. These To support meteorological testing, the EVWP function was installed on a Radar Operations Center (ROC) test bed Radar Product Gen- erator (RPG) and the associated dis- play code was installed on an Open System Prin- cipal User Proces- sor (OPUP). These test bed assets are used to process Level II data col- lected from multi- ple operational Figure 3: KTLX VWP and EVWP comparison Continued on Page 5 page 4 NEXRAD Now VWP Continued from Page 4 WSR-88Ds. To facilitate evaluation of any line. The design of the EVWP function is to pro- improvement provided by the EVWP function, the vide additional wind estimates to augment the wind test code produces an “Original” VWP product and data available for inclusion on the VWP product. an “Enhanced” VWP (EVWP) product that incor- This implementation will not change the basic for- porates the wind estimates selected by the EVWP mat of the VWP product and, therefore, will not function. The example (Figures 2, 3 and 4) is rep- impact downstream processing and display sys- resentative of the test results, to date. tems. 72363 AMA Amarillo Arpt (Awos) 72357 OUN Norman 00Z 03 Mar 2008 University of Wyoming 00Z 03 Mar 2008 University of Wyoming Figure 4: KAMA and KOUN Skew-Ts 00Z March 3, 2008 The EVWP function is still undergoing devel- Joe N Chrisman opmental testing. Results of testing, to date, indi- ROC Engineering Branch cate that the EVWP function consistently provides additional wind estimates not initially available from the legacy VAD/VWP algorithms. Addition- ally, the inclusion of these supplemental wind esti- mates in the VWP product can improve the overall operational usability of the VWP product.