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II. Sources of Tropical Cyclone Wind Field Uncertainty and Approaches to Reducing it

II. Sources of Tropical Cyclone Wind Field Uncertainty and Approaches to Reducing it. Peter G. Black NOAA/AOML Hurricane Research Division Miami, FloridaUSA WMO International Training Workshop on Tropical Cyclone Disaster Reduction Guangdong Meteorological Training Center, Guangzhou, China

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II. Sources of Tropical Cyclone Wind Field Uncertainty and Approaches to Reducing it

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  1. II. Sources of Tropical Cyclone Wind Field Uncertainty and Approaches to Reducing it Peter G. Black NOAA/AOML Hurricane Research Division Miami, FloridaUSA WMO International Training Workshop on Tropical Cyclone Disaster Reduction Guangdong Meteorological Training Center, Guangzhou, China 26-31 March, 2007

  2. Reducing Surface Wind Uncertainty- Key Ingredients • New Airborne Technology Trifecta • Stepped Frequency Microwave Radiometer (SFMR) • Surface Winds • Airborne Tail Doppler radar • 3D structure/fields • GPS dropsondes • Point vertical profile • Define Uncertainty

  3. PERSPECTIVE: The Beauty

  4. Georges (1998) Katrina (2005) Aircraft Perspective Hugo (1989)

  5. PERSPECTIVE: And the Beast

  6. On the ground

  7. The Evolving SystemThe Bridge Across the Valley of Death • AFRC WC-130J • SFMR: 3-5 units, 2007; all 10 units, 2008 • AOC GIV • TA Doppler, SFMR 2008-09 • AOC WP-3D N43RF • SFMR, TA Doppler NOW;SRA 2007, HIRad 2009 • AOC WP-3D N42RF • SFMR, TA Doppler, IWRAPNOW;AWRAP 2008 2002 IHC- Defining the Valley; 2007 IHC- Building the Bridge

  8. SFMR measures C-band microwave emission from foam (air bubbles in the ocean) First flight: Allen, 1980 22 years to assemble bridge components 2003: First OFCM/ AOC bridge- operational SFMR on WP-3D 2004-08: The ‘Golden Gate’ Congressional bridge

  9. Ocean Surface Appearance in Hurricanes: FOAM Streaks- Air Bubbles in the Ocean 200 m Wind speed ~28m/s 200 m Wind Speed ~ 46 m/s

  10. The Evolving System- Capability • SFMR- Surface wind speed and rain rate along track • TA Doppler- 3D wind vector, reflectivity ± 70 km from track; 1-10 km altitude • IWRAP- Surface wind vector and rain rate swath ± 3-5 km from track to 50 m/s; boundary layer 3D wind vector vertical profile along track- 30 m to flight level • AWRAP- Operational version of IWRAP with dual pol • SRA- Surface directional wave spectrum along track: direction, height and wavelength of 3 wave components in real time. • HIRad (next-generation SFMR)- Surface wind speed and rain rate ± 5-8 km from track for WP-3D; ± 40 km from hi level AUV); wind direction in 3-4 years

  11. The Evolving System- Progress • SFMR- • Major wind model upgrade, remove high wind low bias and moderate wind high bias- Uhlhorn, 2005 • Major rain model upgrade- Carswell, 61st IHC-2007 • Major cal upgrade, warm load- ProSensing, 2005 • Add hires land mask, weekly SST field via web uplink- Goldstein • WC-130J fleet SFMR install begins- April, 2007; 3-5 systems by Sept; all 10 by Feb, 2008 • SFMR purchase for GIV • JHT support for calibration, validation and performance improvements in fetch-limited, shallow water conditions: 2005-2007 • Canted off-nadir SFMR installation on N43RF for HIRad algorithm development (?)

  12. The Evolving System- Progress 2 • SRA • Real time algorithm development, 2004-05 • SBIR Phase II award (ProSensing) for operational system, 2006 • Operational SRA install and flight tests, 2007 • AWRAP • SBIR Phase II award (Remote Sensing Systems) for operational IWRAP, 2006 • AWRAP install and flight tests, 2008 • G-IV operational TA Doppler and SFMR • Install and flight tests, 2008

  13. Reducing Wind Field Uncertainty • SFMR flight track strategies • Alpha pattern normal to storm track • Rotated Alpha or ‘Butterfly’ pattern • SFMR cal improvements; shallow water, coastal algo refinements, rain rate algo refinements (JHT supported) • HIRad- broaden SFMR line to a swath enhancing probability of detecting true surface wind max

  14. TA Doppler 23 deg fore/aft scan 70 m pulse AWRAP Frequency: C-band & Ku-band Polarization*: VV, HH, HV & VH Beam Incidence Angles: 30, 35, 41.5, 50 Altitude Range: 500 – 8000 m Range Resolution: 15, 30, 60 & 120 m AWRAP Four channel receiver records Doppler & reflectivity profiles for all four beams simultaneously SRA swath HIRAD Swath: 30-60 deg Conical Scan (60 rpm, 15 m pulse) SFMR 6 frequencies Half Beam: 0 to 10, 12 deg Swath Coverage ~25 – 55 deg. incidence

  15. What is observational uncertainty in hurricanes? 10 0 5 • Horizontal domain relative to storm center • varies according to satellite/aircraft platform • availability. • Vertical domain a function of platform type. • Combination of platform type, domain • coverage and measurement accuracy determines • observational uncertainty.

  16. Reducing Surface Wind Uncertainty- Implementation • Real Time Synthesis Recipe: Template for improved intensity/structure • Real time aircraft communication: ASDL, GLOBALSTAR, INMARSAT • Integration and comparison of 3 independent measures of surface wind • Direct forecaster interaction at NCEP/TPC National Hurricane Center • Key is SFMR

  17. 2005 SFMR Performance • SFMR used in 23 advisories, prompted 2 special advisories • Every SFMR tasking lead to an important conclusion on current intensity or estimates of intensity change- only once per day • Especially crucial for landfall intensity estimates for Dennis, Katrina, Rita and Wilma • Mentioned prominantly in Katrina, Rita and Ophelia NHC storm reports

  18. Hurricane Katrina • Flight-level estimates reduced to the surface suggested Katrina weakened slightly to a CAT4 at landfall • SFMR and GPS dropsondes observed weakening from maximum peak surface winds of 142 kt to 100 kt in 8 h between 29 Aug, 0200 - 1000 GMT • Airborne Doppler analysis showed that the change was near surface, but not at the flight-level of the AF WC-130 (John Gamache JHT presentation)

  19. Air Force 29 Aug 0930 UTC Air Force 29 Aug 0200 UTC

  20. NOAA WSR-88D Radar NOAA GOES IR Satellite Air Force WC-130J Flight Level NOAA WP-3D SFMR NOAA WP-3D DOPPLER

  21. 29 August Hurricane Katrina- SFMR 28 Aug - Peaked profile Vmax=142 kt 29 Aug - Flat profile Vmax=100 kt 28 August * SFMR surface wind — 700 mb flight-level wind ° 700 mb Gradient Wind - - Radial wind • - Vmax NHC estimate Diamond - Vmax Press/Wind Square - GPS 10-m estimate Triangle - GPS 10-m measurement

  22. Doppler Wind Profile - 28 Aug 1725-1820 UTC 12 km SW NE Flight Level 1 km Doppler Wind Profile - 29 Aug 1000-1040 UTC 12 km W NE Flight Level 1 km Dramatic 12-h change in Katrina Wind Profile: CAT5-CAT3

  23. 6 6 9 9 Inflow and shallow wind max to West Outflow and deep wind max to East 12 km • Doppler analyses from 1st W-E leg during Katrina landfall showing asymmetry in horizontal and vertical wind distribution Flight Level 1 km Doppler Winds at 1 km altitude. Peak winds right of track on inbound leg and left of track on outbound leg

  24. NOAA SFMR 29 Aug 0930 UTC Air Force 29 Aug 0930 UTC

  25. NOAA SFMR 29 Aug 1230 UTC Air Force 29 Aug 1230 UTC

  26. Hurricane Michael 1930 GMT, 18 Oct, 2000 AFRC 850 mb flight level reduction (left) SFMR surface measurement (right)

  27. Katrina Summary • Dramatic change in structure and intensity prior to landfall (Weakened from CAT5 to CAT3 intensity in 8 h: 29 Aug, 0200 - 1000 GMT) • Surface wind assessment changed from flight-level reduction to SFMR measurement. • Surface Wind Uncertainty ~ 20% with flight-level data: reduced to ~10% with SFMR & further reduced by Doppler radar observations • Result of real-time and post-storm synthesis: Initial CAT4 from flight level data downgraded to CAT3 in NHC Katrina Report using SFMR and Doppler radar (http://www.nhc.noaa.gov/2005atlan.shtml)

  28. Hurricane Rita Sept 21 Sept 22 Sept 23

  29. Hurricane Rita Sept 21 1900UTC Sept 23 2130UTC

  30. Hurricane Rita

  31. Hurricane Wilma • Transformation due to Yucatan landfall from small, compact CAT 5 Caribbean storm to large, broad CAT 1 Gulf storm • Validated Technology Trifecta synthesis • Similar situation to Katrina: large difference between flight level and surface (> 35%) • Eyewall size (Rmax) increased from 30 to 50 nm while Vmax slowly increased in Gulf (Oct 23, 2100 - Oct 24, 2100 GMT) • Uncertainty of surface wind field reduced with in-situ surface winds

  32. Hurricane Wilma Estimated Surface Winds From 700 mb 24 Oct 0930 UTC 23 Oct 2130 UTC CAT 2 24 Oct 2130 UTC CAT 3 CAT 3 Instead of this….

  33. Hurricane Wilma Observed Surface Winds 24 Oct 0930 UTC Surface Obs 23 Oct 2130 UTC SFMR CAT 1 24 Oct 2130 UTC Surface Obs CAT 2 CAT 2 We have this!

  34. Why rapid intensity change near landfall? • Recent ongoing studies of north Gulf landfalling storms show 80% fill offshore prior to landfall (Rappaport) • Mesoscale ocean features in the Gulf of Mexico, e.g. Loop Current and warm rings, may impact hurricane intensity change (see Shay presentation)

  35. Conclusions • A template has been established for real-time storm intensity and structure change. • Instrument trifecta of SFMR, airborne Doppler radar and GPS dropsonde is essential for real-time interpretation of rapidly changing events, especially near landfall • Continued capability upgrade is essential • SFMR’s on WC-130J aircraft to establish consistency in sampling • Improved airborne Doppler radar capability adding real time IWRAP to TA Doppler for improved boundary layer obs • Higher resolution 4 sample per second UBLOX dropsondes that consistently reach the surface • Improved true real time data transmission via high- speed coms such as AOC INMARSAT/ Globalstar links via efforts of NESDIS (Paul Chang) and Remote Sensing Systems (Jim Carswell)

  36. GPS Dropsonde - Volume Sampled IWRAP inner & outer swath limits 2000 1500 1000 500 0 Dropsonde trajectory Altitude of GPS Dropsonde [m ] Altitude (m) Ground Track 0 2300 m 15 10 5 0 Distance from aircraft [km ]

  37. Preliminary Wind Profile Validation Comparison C-Band VV 31.5 degrees incidence to 6 consecutive dropsondes WIND SPEED WIND DIRECTION 2000 1500 1000 500 0 2000 1500 1000 500 0 Flight level Dropsondes IWRAP Altitude SFMR 100 80 60 40 20 0 [deg] 50 60 70 80 90 100 [m/s] Isabel: Sept. 12, 2003, 18:42:20 to 18:43:42 Z

  38. Wilma Miami 88D

  39. Wilma Miami 88D

  40. Katrina- Slidell 88D

  41. Katrina- Slidell 88D

  42. Rita DOW by J. Wurman Port Arthur

  43. Hurricane Rita Port Arthur, Texas From J. Wurman and F. Masters

  44. Observational Study of Small-Scale Features Present in the Hurricane Boundary Layer Sylvie Lorsolo Atmospheric Science Group Department of Geosciences Texas Tech University 20 October 2006

  45. Subtract Mean to Enhance Perturbations

  46. Characteristic Structure Hurricane Isabel Height =300 m AGL • Horizontal and vertical structure Hurricane Frances Height =300 m AGL

  47. Characteristic Structure (Cont’d) Hurricane Isabel Hurricane Frances

  48. Characteristic Structure (Cont’d) Hurricane Isabel Hurricane Frances

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