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THE USE OF GPS IN RADIOSONDE MEASUREMENTS

THE USE OF GPS IN RADIOSONDE MEASUREMENTS. PRESENTED BY: J. FACUNDO, C. BOWER, & J.FITZGIBBON NOAA/NWS. Observing Systems. Evaluating the Performance of Upper Air GPS Data. Reference Flight Path and Smoothed Wind Speed. Velocity Errors. Position Error. Statistics Raw Velocity Errors.

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THE USE OF GPS IN RADIOSONDE MEASUREMENTS

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  1. THE USE OF GPS IN RADIOSONDE MEASUREMENTS PRESENTED BY: J. FACUNDO, C. BOWER, & J.FITZGIBBON NOAA/NWS

  2. Observing Systems

  3. Evaluating the Performance of Upper Air GPS Data

  4. Reference Flight Path and Smoothed Wind Speed

  5. Velocity Errors

  6. Position Error

  7. Statistics Raw Velocity Errors

  8. Computing Radiosonde Winds [IN-SITU TIME (t), RANGE VALUES SENT TO RRS] 5-METERS 1-SEC [∆t, ∆U, ∆V, ∆HTGPS] BASE STATION/RRS (LOCAL GPS) [t, U, V, HTGPS] [WIND SPEED & DIRECTION COMPUTED IN RRS]

  9. Computing Radiosonde Winds

  10. Computing Radiosonde Winds

  11. Integrating PWVs i,n ∫ d´w = Integrated Precipitable Water (IPW) for ith sensor i,1 PWgps = ΠZw(where Π is a constant of proportionality and Zw is the wet time delay function from the ground to the satellite.* The computed IPWs can be compared with the gps-derived PW to determine the residual IPW *Reference: GPS Meteorology: Direct Estimation of the Absolute Value of Precipitable Water, Jingping Duan, et. al., Journal of Applied Meteorology, 1996

  12. GPS & Radiosonde IPW Comparisons

  13. Consensus View Consensus thresholds In this context, consensus is achieved when most of the measurements fall within a statistically-defined threshold and its bias characteristics are delineated, e.g., 98% fall within 0.5 cm and has an RMSD of 0.2 cm. A set of regression values can also be determined from the base of data collected.

  14. The Future

  15. Prototype CRWVS SURFACE T,P,RH GPS-IPW DATA MANAGEMENT Having pressure measured allows for the possibility for consensus referencing with other technologies who may be using time/height/pressure as their reference.

  16. Sterling Upper Air Operations Sterling Upper Air Operations Sippican MKIIA Rev "I" Functional Precision Sippican MKIIA Rev "I" Functional Precision Geopotential Height vs. Time Pressure vs. Time Flight252 09/11/2004 13:52 UTC Flight253 09/11/2004 17:53 UTC 130 130 120 120 110 110 Elasped Time (minutes) 100 100 ) 90 90 80 80 70 70 60 60 50 50 40 40 30 30 20 20 IAD3-Rev I IAD4-Rev I IAD4-Rev I IAD3-Rev I 10 10 0 0 0 0 100 5 200 10 300 400 15 500 20 600 700 25 800 30 900 1000 35 Geopotential Height (km) Pressure (hPa) IAD4 IAD3 IAD3 IAD4 GPS-derived Pressures

  17. GPS height measurements agreed on average to within ± 20 m from the surface to 34 km. At 30 km pressure sensors were in error by values between -70m (Vaisala) up to +120m (SRS). The pressure sensors considered were of extremely good quality compared to earlier generations of sensors, but were unable to provide very reliable heights at pressures lower than 10 hPa. GPS Geopotential Height Differences vs Hypsometric calculations

  18. Composite Moisture Referencing TOP ~99. 9% 30-32 km ~99. 7% ~98 % GPS-IPW (cm)-Reference CFH/SNOWHITE SOUNDING WV (g/kg) RUC MODEL OUTPUT IPW (cm) 15-18 km SATELLITE IPW (cm) NPOES SOUNDER WV (g/kg) RADIOSONDE IPW (cm) RADIOSONDE SOUNDING (RH (%) TO WV (g/kg) CFH/SNOWHITE IPW (cm) AIRCRAFT SOUNDING (RH (%) TO WV (g/kg) LIDAR/MWV SOUNDING (g/kg) LIDAR/MWV IPW (cm) AIRCRAFT IPW (cm) SFC SFC RH/ASOS

  19. The IPW Weather Spectrum 10.0 8.0 IPW (CM) 5.0 0.5 Severe WX Tropical WX Convective WX Heavy Snow/Clear Very Hot/Cold Clear Sky Frontal WX Snow/Clear

  20. RUC

  21. Conclusions • GPS has become increasing critical for measuring the upper atmosphere • Demonstrates great reliability and measurement accuracy/precision • In the future, psuedo-pressure profiles can be derived directly from high-resolution GPS-computed heights. Note, industry already doing this for their commercial systems • Can serve as an independent reference • New applications on the way

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