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Radar Covergare Comparison

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The West Coast of Washington and the NE and SW corners of Wyoming are regions of the contiguous United States where NEXRAD coverage is incomplete. One approach to addressing these gaps is to install …

The West Coast of Washington and the NE and SW corners of Wyoming are regions of the contiguous United States where NEXRAD coverage is incomplete. One approach to addressing these gaps is to install additional NEXRAD-class radars. Another potential approach is to install small radar networks of the type being investigated in the CASA project. This paper compares these two approaches. We provide a meteorological and user-need assessment of present radar coverage in these regions (based on a recent feasibility study led by J. Brotzge [1]) as well as an objective assessment of the radar-coverage that would be achieved using the large radar and small radar approaches.


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  • 1. Outline• Introduction• Long-Range Vs. Short-Range Radar deployments• Possible Radar Solutions – Idealized radar Calculations – Coverage for Example radar networks – Radar Coverage simulations (Wyoming/ Washington)• Cost Considerations – Long-range radar – Short-range radar• Summary
  • 2. Introduction• Severe tornado events in northeastern Wyoming and a three-day coastal storm system in Washington raised awareness of the radar coverage gaps if the observation current system (NEXRAD)• These coverage gaps have several causes: the distance between radars (345 km in the western United States); radar beam blockage due to mountains and other terrain.• A study that assesses the meteorological need for and the feasibility of deploying additional radars to augment the current radar observing system in northeastern and southwestern Wyoming and coastal Washington was funded by a contract from NOAA to CASA through the University of Oklahoma with Dr. Jerry Brotzge as Principal Investigator [1]This work was primarily supported by the Engineering Research Center Program of theNational Science Foundation under NSF Award Number 0313747. Any opinions, findingsand conclusions or recommendations expressed in this material are those of the authorand do not necessarily reflect of the National Science Foundation.
  • 3. Wyoming• The gap regions in Wyoming lack radar coverage because of the distance between radars and mountain blockage. In Campbell County, no radar coverage is available below 3 km AGL, and only 24% of Johnson County and 39% of Sweetwater County have coverage below 3 km AGL.• Low-level radar coverage is needed for routine detection of snow, flooding rains, and low-topped thunderstorms (Top) The County Warning Forecast Areas of Wyoming. Figures courtesy of the NWS (http://www.weather.gov/mirs/public/prods/maps/state_list_cwfa.htm). (Bottom) The existing radar coverage at heights 1 km (yellow), 2 km (red) and 3 km (blue) AGL. Interstate highways are marked in red and county outlines are marked in black.
  • 4. Washington• Radar coverage gaps in coastal Washington are primarily caused by beam blockage. Much of the region is blocked by the Olympic Mountains to the west, and so there is virtually no coverage over the ocean where the majority of western Washingtons weather hazards originate• Flooding and severe (non-thunderstorm) winds are the primary weather threats to western Washington state. While the number of severe weather events is relatively low, these events are typically large in scale, duration, and severity.• High vulnerability in the coastal counties Jefferson, Grays Harbor, Pacific because the lack low-level (< 3 km AGL) radar coverage The County Warning Forecast Areas of western Washington. Figure courtesy of the NWS: (http://www.weather.gov/mirs/public/prods/maps/state_list_cwfa.htm). (Bottom) The existing radar coverage at heights 1 km (yellow), 2 km (red) and 3 km (blue) AGL. Interstate highways are marked in red and county outlines are marked in black.
  • 5. Long-range radars Vs. short-range radar 14.0°NEXRAD Operating frequency WSR-88D 2.7 – 3.0 CASA 9.41 GHz CASA 11.0° GHz E-SCAN PANELS Wavelength 10.0 cm 3 cm Antenna diameter 8.53 m 1.20 m Antenna gain Antenna beamwidth 45.5 dB 1.0º 38 dB 1.8º 9.0° Range gate spacing 250 m 100 m Maximum rotation rate 36 deg s-1 35 deg s-1 Acceleration rate 15 deg s-2 50 deg s-2 Average transmitter 1.56 kW 9 W/pol power Peak transmitter power 750 kW 7.5 kW/pol 7.0° Min. Detect. Reflect. -23 dBZ -2 dBZ (10 km) CASA IP1 Pulse repetition 318-452 1.6, 2.4 kHz frequency 318-1304 pulses/sec 5.0° Pulse width 1.6, 4.5-5.0 660 nsec μ sec Dual-polarization For 2010- Yes 2012 3.0° 2.0° 1.0° PR1 First Off the Grid (Stefani) Radar Radar Tested At “Storm signatures are detected with higher temporal Chill/CSU and spatial resolution with PR1 data and the radar seems to be functioning correctly” - Israel Matos (MIC)
  • 6. Possible radar solutions Wyoming WYOMING STATE 165 km Domain A: Area: 165x165 km2 Counties: Short Range Long Range 165 km • Sheridan • Johnson • Campbell Rmax=40km Rmax=230km Domain B: Rspacing=35km Rspacing=225km Area: 210x141 km2 Counties: 3dB 3dB • Sweetwater el _ min   0.9o el _ min   0.5o 210 km 2 2 LEGEND No cone of silence area No cone of silence area 141 km 2km<H<3km Triangular Grid Triangular Grid  1km<H<2km  H<1km Vertical Coverage Wyoming Domain A (160km x160km) Wyoming Domain A Height H:1km Coverage: 1e+002% 4 0 0.9 3.5 20 Wyoming – Domain 0.8 Heigh above Ground level (km) 3 40 160km A 2.5 0.7 60• Small nodes: 18 0.6• Large nodes: 01 Range in km 2 80 0.5 0.4 1.5 100 Vertical Coverage 0.3 Coverage in Plan view- Wyoming Domain A 1 120 Wyoming Domain A(160km x 160km) Height H:1km CoverageS: 69% 4 0 0.2 0.5 140 0.9 162 km 3.5 0.1 20 0.8 0  160 Heigh above Ground level (km) 0 5 10 15 20 25 30 35 0 3 50 100 150 40 Distance (km) Range in km 0.7 2.5 60 0.6 Range in km 2 80 0.5 Wyoming – Domain 0.4 1.5 100 B 138 km 0.3 • Small nodes: 16 1 120 0.2 • Large nodes: 01 0.5 140 0.1 0   160 0 50 100 150 200 0 50 100 150 Distance (km) Range in km
  • 7. Possible radar solutions Washington Short Range Long Range WASHINGTON STATE Rmax=40km Rmax=230km Domain C: Area: ~360x160 km2 Rspacing=35km Rspacing=225km 360 km Counties: 3dB  • Lewis el _ min   0.9o el _ min  3dB  0.5o • Pacific • Thurston 2 2~60 nmi 160 km • Pierce • King No cone of silence area No cone of silence area • Kitsap • Mason  Triangular Grid Triangular Grid • Grays Harbor  LEGEND 2km<H<3km Washington Domain C(360km x 160km) 1km<H<2km Vertical Coverage - Washington Domain C(360km x 160km) Height H:1km Coverage: 83% 4 0 H<1km 0.9 3.5 50 0.8 3 100 0.7 Heigh above Ground level (km) 2.5 0.6 150 Range in km Washington Domain C(260km x 140km) Vertical Coverage - Washington Domain C(260km x 140km) 2 Height H:1km Coverage: 37% 0.5 4 0 200 3.5 0.9 0.4 1.5 50 0.8 141km 3 Heigh above Ground level (km) 250 0.3 0.7 1 2.5 100 0.6 Range in km 0.2 2 300 0.5 0.5 150 1.5 0.4 0.1 0.3 1 350 256 km 0  200 0 5 10 15 20 25 30 35 0 50 100 150 200 250 300 350 0.2 Distance (km) 0.5 Range in km 0.1 250 0  0 50 100 150 200 0 50 100 150 200 250 Distance (km) Range in km
  • 8. Idealized Radar Calculations Number of Radars vs. Domain Size Coverage Percentage vs. Altitude for Short-range and Long-range Radar Spacing for Short-range and Long-range Radar Spacings 100 35 Short Ideal Grid 90 Long Ideal Grid 30 80 Coverage Percentage (%) Short Ideal GridNumber of Radars 25 70 Long Ideal Grid 60 20 50 15 40 10 30 5 20 0 10 50 100 150 200 Domain Size (km) 0 0 0.5 1 1.5 2 2.5 3 Altitude (km) a) b)a) Number of radars needed to populate a given domain size for short-range (35 km) and long-range (225 km) radar spacing. The domain considered is square with the side of the squaredefined by the "domain size" in kilometers. b) Percent coverage evaluated at a given altitudefor short-range (35 km) and long-range (225 km) radar spacing. Percent coverage is evaluatedat the center of the radar beam, 0.9 deg and 0.5 deg for the short-range and long-rangeradars, respectively, and takes into consideration the curvature of the earth.
  • 9. Radar Coverage Simulations• Illustration of height of the radar beam (AGL) for 3 km a) "smooth-earth" coverage calculations and b) those over terrain. Note that when height is given 2 km as AGL the height is relative to the terrain. 1 km• The radar beam is considered blocked when the path integrated occultation is greater than 50%. a)• The blockage calculations were performed using the University of Oklahoma’s Advance Regional 3 km prediction System (ARPS). 2 km• Geospatial analysis and visualization was 1 km performed using Geographic Resources Analysis Support System (GRASS) Support System (GRASS) and Geographic Information System (GIS). b)
  • 10. Radar Coverage Wyoming Domain A WYOMING STATE + + + + WYOMING STATE + Domain A: Area: 165x165 km 2 + + + Domain A: Area: 165x165 km2 Counties: + + + Counties: • Sheridan • Sheridan • Johnson + + + + + • Johnson • Campbell • Campbell + + + + # Radars LEGEND Domain A • Short : 21 • Long : 01 + 2km<H<3km 1km<H<2km H<1km WYOMING STATE Domain A: Area: 165x165 km 2 Counties: • Sheridan • Johnson • Campbell Coverage Percentage vs. Altitude for Wyoming Domain A (165km x 165km) LEGEND Long-range radars: 1 Short-range radars: 21 100 2km<H<3km 1km<H<2km 90 Altitude Coverage (%) Coverage (%) H<1km 80 (m) Long (1 radar) Short (21 Coverage Percentage (%) radars) 70 100 1% 7% 60 Short (Smooth) 500 25% 71% Long (Smooth) 1000 61% 90%WYOMING STATE LEGEND 50 Short (Terrain) 2000 96% 95% Long (Terrain) 3000 99% 97%Domain A: 2km<H<3km 40Area: 165x165 1km<H<2kmkm2 30Counties: H<1km • Sheridan 20 • Johnson 10 • Campbell 0 0 0.5 1 1.5 2 2.5 3 Altitude (km)
  • 11. Radar Coverage Wyoming WYOMING STATE WYOMING STATE Domain B: Domain B: Area: 210x141 Area: 210x141 km 2 km2 Counties: Counties: • Sweetwater • Sweetwater # Radars • Short : 21 + LEGEND • Long : 01 2km<H<3km 1km<H<2km H<1km Domain B + + + + + + + + + + + + + + + + + WYOMING STATE + + + + Domain B: Area: 210x141 km 2 Counties: • Sweetwater Coverage Percentage vs. Altitude for Wyoming Domain B(210km x 141km) LEGEND Long-range radars: 1 Short-range radars: 21 100 2km<H<3km 1km<H<2km 90 H<1km 80 Coverage Percentage (%) Altitude Coverage (%) Coverage (%) 70 (m) Long Short Short (Smooth) (1 radar) (21 radars) 60 Long (Smooth) 100 0% 5% Short (Terrain) 500 14% 80% 50 1000 49% 98% WYOMING STATE Long (Terrain) LEGEND 2000 93% 99% Domain B: 402km<H<3km Area: 210x141 km2 3000 100% 99% Counties: 301km<H<2km • Sweetwater H<1km 20 10 0 0 0.5 1 1.5 2 2.5 3 Altitude (km)
  • 12. Radar Coverage Washington WASHINGTON Domain C: Area: ~360x160 km2 Counties: • Lewis • Pacific Domain C • Thurston • Pierce • King + + + + • Kitsap + + + • Mason ~60 nmi + + + + + • Grays Harbor + + + + + + + + + + # Radars • Short : 27 + WASHINGTON STATE + + + + + • Long : 01 LEGEND Domain C: Area: ~360x160 km 2 2km<H<3km Counties: 1km<H<2km • Lewis, Pacific, Thurston, Pierce H<1km • King, Kitsap, Mason, Grays Harbor Coverage Percentage vs. Altitude for Washington Domain C(360 km x 160 km) Long-range radars: 1 Short-range radars: 27 100 90 80 Altitude Coverage (%) Coverage (%) Coverage Percentage (%)ATE 70 (m) Long Short LEGEND (1 radar) (27 radars) WASHINGTON STATE 60 100 1% 3% 2km<H<3km Domain C: 500 15% 45% Area: 1km<H<2km 2 ~360x160 km 50ston, Pierce Short (Smooth) 1000 37% 67% Counties: H<1km 2000 74% 72%n, Grays Harbor 40 Long (Smooth) • Lewis, Pacific, Thurston, Pierce • King, Kitsap, Mason, Grays Harbor Short (Terrain) 3000 94% 73% 30 Long (Terrain) 20 LEGEND 10 2km<H<3km 0 1km<H<2km 0 0.5 1 1.5 2 2.5 3 Altitude (km) H<1km
  • 13. Cost Considerations• For long-range radar, site selection, land preparation, site access, tower, communication and electrical power, represent a complicated process that in most cases takes from one to 3 years.• An estimate for the up-front cost for a long- range S-band radar (including the costs to buy and install the radar as well as the land and supporting infrastructure) is $10M. This figure was cited in 2008 in a National Research Photo of a state-of-the-art phased array radar system. Council report (NRC 2008) based on a Lincoln Phased arrays cost $1M/m2 today. Laboratory estimate. This estimate is derived based on the fact that the 156 radar WSR- E-SCAN PANELS 88D/NEXRAD radar network cost $1.56 billion to deploy between 1990 and 1997, or ~ $10M per radar.• For short-range radar, CASA project has set an aim-point of $200k as the up-front cost of each radar in a dense radar network and per-site recurring cost of $20k per radar per year. Artistic concept of CASA radar panels attached to a cellular telephone tower and the sides of a building.
  • 14. Summary• Additional weather radar, strategically placed along and near critical weather-sensitive industries and infrastructure in radar gap regions, may improve public safety and reduce weather-imposed economic loss. Beyond simply filling gaps in existing coverage, additional radar capabilities such as rapid scanning, higher spatial resolution and multi- Doppler coverage and enhanced radar products such as provided by dual-polarization have the potential to significantly improve current observing and predicting capabilities.• Forty-two small X-band radars (21 radars in NE Wyoming and 21 radars in SW Wyoming) or two large S-band radars (one in each region), could provide this coverage. The 42 short-range (X-band) radars, deployed strategically along critical infrastructure, would provide extensive multi-Doppler coverage of wind and rain at low-levels (below 2 km AGL), thereby enabling real-time monitoring and improved prediction of warm-season severe thunderstorms and low-level winter weather. Two long-range weather radars could provide equivalent coverage at and above 2 km AGL.• A network of 27 short-range radars, deployed along the coast, would provide multi- Doppler coverage as low as 1 km AGL along the coast and up to a distance of 40 km from shore. Over terrain, high resolution radar observations would help quantify locally intense terrain-forced precipitation improving QPE and identifying low-level wind hazards.
  • 15. ReferencesJerry Brotzge, Robb Contreras, Brenda Phillips and Keith Brewsterl, “Radar Feasibility Study,” January 31, 2009.D. J McLaughlin, et al, “Distributed Collaborative Adaptive Sensing (DCAS) for Improved Detection, Understanding and Predicting of Atmosphere Hazards,” in Proc of 85th AMS Annual Meeting 2005, San Diego, CA.Brotzge, J., K. Brewster, V. Chandrasekar, B. Philips, S. Hill, K. Hondl, B. Johnson, E. Lyons, D. McLaughlin, and D. Westbrook, 2007: “CASA IP1: Network operations and initial data”. Preprints, 23rd International Conf. on Interactive Information Processing Systems (IIPS) for Meteor., Ocean., and Hydrology, AMS Conf., San Antonio, TX.Gorgucci, E., and V. Chandrasekar, 2005: “Evaluation of attenuation correction methodology for dual-polarization radars: Application to X-band systems”, J. Atmos. Oceanic Technol., 22, 1195-1206.Brewster, K., E. Fay and F. Junyent, 2005: How will X-band attenuation affect tornado detection in the CASA IP1 radar network?, 32nd Conference on Radar Meteorology, Albuquerque, NM, AMS, Boston. Conference CD, Paper 14R.4.Brotzge, J., D. Andra, K. Hondl, and L. Lemon, 2008: “A case study evaluating Distributed, Collaborative, Adaptive Scanning: Analysis of the May 8th, 2007, minisupercell event”. Preprints, Symposium on Recent Developments in Atmospheric Applications of Radar and Lidar, AMS Conf., New Orleans, LA.Cheong, B. L., K. Hardwick, J. Fritz, P. S. Tsai, R. Palmer, V. Chandrasekar, S. Frasier, J. George, D. Brunkow, B. Bowie, P. Kennedy, 2007: “Refractivity retrieval using the CASA X-band radars.” Preprints, Proceedings of AMS 33rd Conference on Radar Meteorology, Cairns, Australia.Leone, D., R. Endlich, J. Petričeks, R. Collis, and J. Porter, 1989: “Meteorological considerations used in planning the NEXRAD network.” Bull. Amer. Meteor. Soc., 70, 4–13.
  • 16. Backup slides
  • 17. 500 current radar units reach end of life 2012 – 2025 Red: sustain, replace legacy radars; Blue: large MPAR solution (~ same coverage) 10000 Small CASA Radars - Acquisition: 9000 10,000 radars x $100k per radar = $1B 2012 – 2016 8000 O&M will be a key factor – to be modeled 7000 Legacy O&M Cost 6000 Large MPAR Acquisition: Legacy Replacement Cost Millions Total Legacy Cost 5000 320 radars x $10M per radar = $3.2B 2012 - 2016 Legacy and MPAR O&M Cost MPAR Acquisition Cost 4000 Total Cost with MPAR 3000 2000 1000 0 11 13 15 17 19 21 23 25 27 29 20 20 20 20 20 20 20 20 20 20 Year1/13/2012 1:45:46 PM HiLo1 ECE697V Fall 2008 18