Evaluation of Wind Vectors observed by ASCAT using Statistical Distributions <ul><li>Naoto EBUCHI </li></ul><ul><li>Instit...
Outline <ul><li>Comparison of ASCAT wind vectors with data from ocean buoys </li></ul><ul><li>Assessment of statistical di...
Monthly Report on Buoy Comparison by KNMI
Buoy Data for Comparison with ASCAT <ul><li>Data Period </li></ul><ul><li>- From 20 Nov. 2008 to 31 Dec. 2010  </li></ul><...
Comparison of ASCAT Winds with Buoy Data <ul><li>  #   Bias   RMS Correlation </li></ul><ul><li>Wind Speed (m/s) 27,247  -...
Calculation of Global Statistics of ASCAT Wind Speeds and Directions <ul><li>ASCAT 25 km Swath Products (L2) </li></ul><ul...
ASCAT Global Wind Speed Histograms <ul><li>Period: 1 Jan. 2010 – 31 Dec. 2010 (1 year) </li></ul><ul><li>Area: global ocea...
ECMWF Wind Speed Histograms <ul><li>Collocated with ASCAT observations </li></ul>
Statistics of ASCAT Wind Speed Distribution ASCAT NWP
Statistics of ASCAT Wind Speed Distribution ASCAT NWP 12.5 km Product
ASCAT Wind Direction Histograms Left Swath,  Wind Speed Range: 7-9 m/s, Descending Paths WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 1...
Normalized ASCAT Wind Direction Histograms WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 10-12 WVC# 13-15 WVC# 16-18 WVC# 19-21 Descendi...
Wind Speed Dependence of Normalized Wind Direction Histograms (Outer Cells) Normalized (ASCAT/NWP),   WVC#: 1-3 (Left Oute...
Wind Speed Dependence of Normalized Wind Direction Histograms (Mid Cells) Normalized (ASCAT/NWP),   WVC#: 10-12 (Left Mid ...
Wind Speed Dependence of Normalized Wind Direction Histograms (Inner Cells) Normalized (ASCAT/NWP),   WVC#: 19-21 (Left In...
Applications to data  from Oceansat-II scatterometer Oceansat-II Scatteromter (OSCAT) Ku-band (13.51 GHz) Scanning dual pe...
Comparison of  OSCAT  Winds with Buoy Data <ul><li>  #   Bias   RMS Correlation </li></ul><ul><li>Wind Speed (m/s)  8,938 ...
OSCAT  Global Wind Speed Histograms <ul><li>Period: 1 Jan. 2010 – 31 Dec. 2010 (1 year) </li></ul><ul><li>Area: global oce...
ECMWF Wind Speed Histograms <ul><li>Collocated with  OSCAT  observations </li></ul>
Statistics of  OSCAT  Wind Speed Distribution OSCAT Asc NWP OSCAT Dec ECMWF Asc ECMWF Dec
OSCAT  Wind Direction Histograms Left Swath,  Wind Speed Range: 7-9 m/s, Ascending Paths WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 1...
Summary <ul><li>ASCAT wind speeds and directions agrees well with buoy observations in general. </li></ul><ul><li>ASCAT gl...
 
Comparison of wind speed
Residuals of Wind Speed and Direction
Residuals of Wind Speed and Direction   Binning wind speed = (U buoy  + U scat )/2
Dependence of Wind Speed Residual on Wave Parameter Significant Wave Height Inverse Wave Age Correlation Coefficient = 0.3...
Comparison of wind speed OSCAT
Residuals of Wind Speed and Direction   Binning wind speed = (U buoy  + U scat )/2 OSCAT
Statistics of  NSCAT  Wind Speed Distribution ASCAT ASCAT ASCAT ASCAT (Ebuchi,  J. Oceanogr ., 2000)
Statistics of  QSCAT  Wind Speed Distribution ASCAT ASCAT ASCAT ASCAT Ascending Descending
Histograms of  ERS-1  Wind Directions CMOD-4 CMOD-IFR2 (Ebuchi & Graber,  JGR , 1998)
Histograms of  NSCAT  Wind Directions (Ebuchi,  JGR , 1999)
Histograms of  QSCAT  Wind Directions (Ebuchi,  Proc. IGARSS 2000 , 2000)
Rough estimation of incidence angle error   <ul><li>Based on the SASS-2 GMF (Wentz et al., 1984) </li></ul><ul><li>At an i...
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EVALUATIONS OF WIND VECTORS OBSERVED BY ASCAT USING STATISTICAL DISTRIBUTIONS

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EVALUATIONS OF WIND VECTORS OBSERVED BY ASCAT USING STATISTICAL DISTRIBUTIONS

  1. 1. Evaluation of Wind Vectors observed by ASCAT using Statistical Distributions <ul><li>Naoto EBUCHI </li></ul><ul><li>Institute of Low Temperature Science, Hokkaido University </li></ul><ul><li>[email_address] </li></ul>MetOp-A
  2. 2. Outline <ul><li>Comparison of ASCAT wind vectors with data from ocean buoys </li></ul><ul><li>Assessment of statistical distributions of ASCAT wind speeds and directions </li></ul><ul><ul><li>Global wind speed histograms </li></ul></ul><ul><ul><li>Directional distributions relative to antenna beams </li></ul></ul><ul><li>Applications to Oceansat-II scatterometer </li></ul>
  3. 3. Monthly Report on Buoy Comparison by KNMI
  4. 4. Buoy Data for Comparison with ASCAT <ul><li>Data Period </li></ul><ul><li>- From 20 Nov. 2008 to 31 Dec. 2010 </li></ul><ul><li>Collocation </li></ul><ul><li>-  r < 12.5 km,  t<10 min. </li></ul><ul><li>Height and Stability Collections </li></ul><ul><li>- Liu and Tang (1996) Code </li></ul><ul><li>- 10-m height Neutral Equivalent Wind </li></ul>NDBC NDBC TAO PIRATA KEO RAMA WHOI
  5. 5. Comparison of ASCAT Winds with Buoy Data <ul><li> # Bias RMS Correlation </li></ul><ul><li>Wind Speed (m/s) 27,247 -0.15 1.42 0.885 </li></ul><ul><li>Wind Direction (deg.) </li></ul><ul><li> U > 0 m/s 26,976 3.0 26.2 0.957 </li></ul><ul><li> U > 3 m/s 23,750 2.7 17.4 0.979 </li></ul><ul><li> U > 5 m/s 18,672 2.7 14.1 0.985 </li></ul>
  6. 6. Calculation of Global Statistics of ASCAT Wind Speeds and Directions <ul><li>ASCAT 25 km Swath Products (L2) </li></ul><ul><li>1 Jan. 2010 – 31 Dec. 2010 (1 year) </li></ul><ul><li>Global ocean, 60 o S – 60 o N </li></ul><ul><li>Collocated ECMWF winds (Non-EN wind) </li></ul><ul><li>156 million data points </li></ul>
  7. 7. ASCAT Global Wind Speed Histograms <ul><li>Period: 1 Jan. 2010 – 31 Dec. 2010 (1 year) </li></ul><ul><li>Area: global ocean, 60 o S – 60 o N </li></ul><ul><li>Bin size: 1 m/s </li></ul>
  8. 8. ECMWF Wind Speed Histograms <ul><li>Collocated with ASCAT observations </li></ul>
  9. 9. Statistics of ASCAT Wind Speed Distribution ASCAT NWP
  10. 10. Statistics of ASCAT Wind Speed Distribution ASCAT NWP 12.5 km Product
  11. 11. ASCAT Wind Direction Histograms Left Swath, Wind Speed Range: 7-9 m/s, Descending Paths WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 10-12 WVC# 13-15 WVC# 16-18 WVC# 19-21 ECMWF ASCAT
  12. 12. Normalized ASCAT Wind Direction Histograms WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 10-12 WVC# 13-15 WVC# 16-18 WVC# 19-21 Descending Ascending Normalized (ASCAT/NWP), Left Swath, Wind Speed Range: 7-9 m/s
  13. 13. Wind Speed Dependence of Normalized Wind Direction Histograms (Outer Cells) Normalized (ASCAT/NWP), WVC#: 1-3 (Left Outer Swath) Descending Ascending 3-5 m/s 5-7 m/s 7-9 m/s 9-11 m/s 11-13 m/s 13-15 m/s
  14. 14. Wind Speed Dependence of Normalized Wind Direction Histograms (Mid Cells) Normalized (ASCAT/NWP), WVC#: 10-12 (Left Mid Swath) Descending Ascending 3-5 m/s 5-7 m/s 7-9 m/s 9-11 m/s 11-13 m/s 13-15 m/s
  15. 15. Wind Speed Dependence of Normalized Wind Direction Histograms (Inner Cells) Normalized (ASCAT/NWP), WVC#: 19-21 (Left Inner Swath) Descending Ascending 3-5 m/s 5-7 m/s 7-9 m/s 9-11 m/s 11-13 m/s 13-15 m/s
  16. 16. Applications to data from Oceansat-II scatterometer Oceansat-II Scatteromter (OSCAT) Ku-band (13.51 GHz) Scanning dual pencil beam VV and HH pol 50 km resolution 1800 km swath
  17. 17. Comparison of OSCAT Winds with Buoy Data <ul><li> # Bias RMS Correlation </li></ul><ul><li>Wind Speed (m/s) 8,938 0.56 1.65 0.893 </li></ul><ul><li>Wind Direction (deg.) </li></ul><ul><li> U > 0 m/s 8,835 -0.2 32.4 0.938 </li></ul><ul><li> U > 3 m/s 7,550 -0.3 22.3 0.968 </li></ul><ul><li> U > 5 m/s 6,130 -0.4 14.1 0.977 </li></ul>
  18. 18. OSCAT Global Wind Speed Histograms <ul><li>Period: 1 Jan. 2010 – 31 Dec. 2010 (1 year) </li></ul><ul><li>Area: global ocean, 60 o S – 60 o N </li></ul><ul><li>Bin size: 1 m/s </li></ul>
  19. 19. ECMWF Wind Speed Histograms <ul><li>Collocated with OSCAT observations </li></ul>
  20. 20. Statistics of OSCAT Wind Speed Distribution OSCAT Asc NWP OSCAT Dec ECMWF Asc ECMWF Dec
  21. 21. OSCAT Wind Direction Histograms Left Swath, Wind Speed Range: 7-9 m/s, Ascending Paths WVC# 1-3 WVC# 4-6 WVC# 7-9 WVC# 13-15 WVC# 16-18 WVC# 10-12 ECMWF OSCAT
  22. 22. Summary <ul><li>ASCAT wind speeds and directions agrees well with buoy observations in general. </li></ul><ul><li>ASCAT global wind speed histogram varies with cross-track cell location. This trend is clearly represented by statistical parameters, such as standard deviation, skewness and kurtosis. </li></ul><ul><li>Directivity relative to the antenna beams is discernible for ASCAT wind directions. </li></ul><ul><li>At low wind speeds and the outer cells (high incidence), most of wind vectors aligned to the flight direction or mid-beam direction. </li></ul><ul><li>These results suggest the needs for further refinements of the wind retrieval algorithms and the C-band GMF. </li></ul>
  23. 24. Comparison of wind speed
  24. 25. Residuals of Wind Speed and Direction
  25. 26. Residuals of Wind Speed and Direction Binning wind speed = (U buoy + U scat )/2
  26. 27. Dependence of Wind Speed Residual on Wave Parameter Significant Wave Height Inverse Wave Age Correlation Coefficient = 0.300 Correlation Coefficient = -0.311
  27. 28. Comparison of wind speed OSCAT
  28. 29. Residuals of Wind Speed and Direction Binning wind speed = (U buoy + U scat )/2 OSCAT
  29. 30. Statistics of NSCAT Wind Speed Distribution ASCAT ASCAT ASCAT ASCAT (Ebuchi, J. Oceanogr ., 2000)
  30. 31. Statistics of QSCAT Wind Speed Distribution ASCAT ASCAT ASCAT ASCAT Ascending Descending
  31. 32. Histograms of ERS-1 Wind Directions CMOD-4 CMOD-IFR2 (Ebuchi & Graber, JGR , 1998)
  32. 33. Histograms of NSCAT Wind Directions (Ebuchi, JGR , 1999)
  33. 34. Histograms of QSCAT Wind Directions (Ebuchi, Proc. IGARSS 2000 , 2000)
  34. 35. Rough estimation of incidence angle error <ul><li>Based on the SASS-2 GMF (Wentz et al., 1984) </li></ul><ul><li>At an incidence angle of  = 57 o , VV-pol., and wind speed of U 10 = 10 m/s, </li></ul><ul><li>d  0 / d  = – 0.3 dB </li></ul><ul><li>d  0 / d U 10  = 0.7 dB </li></ul><ul><li>An error of 1 o in incidence angle may cause an error of 0.4 m/s in wind speed. </li></ul>
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