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Experimental Uses of QuikSCAT at TPC and Future Requirements

NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION. Experimental Uses of QuikSCAT at TPC and Future Requirements. Jack Beven Hurricane Specialist, Tropical Prediction Center Chris Hennon Visiting Scientist, UCAR, Tropical Prediction Center. Outline.

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Experimental Uses of QuikSCAT at TPC and Future Requirements

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  1. NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION Experimental Uses of QuikSCAT at TPC and Future Requirements Jack Beven Hurricane Specialist, Tropical Prediction Center Chris Hennon Visiting Scientist, UCAR, Tropical Prediction Center

  2. Outline • Operational Applications and Examples of QuikSCAT • Applied Research • Auto center detection • Dealing with rain • Future • WindSat • Operational Requirements and Desires

  3. Does a circulation center exist? Is this center fix accurate? Is this a valid representation of the 34 kt. wind radii? Is 50 kt an accurate MSW measurement? How timely is the QSCT Pass? Isabel (45 kt from Dvorak)

  4. Operational Examples

  5. A good center location

  6. A bad example - QuikSCAT can fail to detect circulation centers, even in tropical storms or hurricanes Erika (45 kt from aircraft)

  7. When a center is found, it is frequently in the wrong place Fausto (2003) – distance between positions = 56 mi NRCS analysis may provide a more accurate center

  8. QuikSCAT Research at TPC

  9. Auto Center Detection • Motivation • For TDs and TSs, QuikSCAT solution contains a discernable fix about 35% of the time • The ambiguity field may contain a circulation center not shown in the solution field • In general, operational time constraints do not allow a manual ambiguity analysis • An automated ambiguity analysis procedure will identify any possible circulations and assign a confidence level to each • Confidence based on directional probabilities embedded in data

  10. Draw 4 x 4 degree (or user specified size) box around chosen location

  11. Rain Contamination • Rain severely limits QuikSCAT usefullness for: • Wind Radii estimation (esp. 50 and 64 kt.) • Circulation center detection • Maximum wind estimation • Can we ‘correct’ the retrieved wind speeds based on the rain rate?

  12. Operational Rain Correction? • Need QuikSCAT retrieved wind speed, hi-res rain rate, and ‘true’ wind speed to develop an algorithm • Accurate rain rate generally not available (no radiometer on board) • Good surface wind speed analysis for TCs difficult if not impossible in most situations • Can MUDH rain probability serve as a proxy for rain rate? • MUDH considers brightness temperature and normalized beam difference – two parameters that should be correlated with rain rate • If so, than a correction algorithm may be developed • Two TRMM/QuikSCAT coincident passes analyzed

  13. Can WindSat Provide Usuable TC Retrievals?

  14. Fabian (2003)- Verification against QSCAT Rain Not Likely Rain Likely

  15. Verification against surface wind analysis (Fabian 3 Sep. 2003 2147 UTC) Very Large (> 10 m/s) differences over much of the storm H*Wind Wind Speed Highest differences exactly match heavy rain areas WindSat Rain Rate (experimental) Generally good agreement around storm periphery WindSat – H*Wind Figures courtesy of Ian Adams (UCF)

  16. Isabel (2003) QuikScat September 15 Windsat September 14 WindSat figure courtesy of Zorana Jelenak (NESDIS)

  17. Summary • QuikSCAT has been useful in many cases for operational application • Center detection, location, wind radii • Rain impacts and lack of rain information severly limits further use of QuikSCAT winds • Preliminary TC WindSat looks not encouraging • Development continues

  18. Requirements for Future Missions • Wind measuring instrument and rain detection instrument on the same satellite – CMIS instrument on NPOESS will fulfill this • Less ambiguity in the measurements • More coverage! • New techniques (physical, model function) • Limit rain effects • Developed specifically for tropical cyclones

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