VALIDATION AND EVALUATION OF QUIKSCAT ULTRA-HIGH RESOLUTION WIND

							 Amanda M. Plagge, University of New Hampshire
Doug C. Vandemark, University of New Hampshire
        David G. Long, Brigham Young University
    Coastal Wind
   Difficulties with forecasting in coastal areas (land-
    ocean and atmosphere-ocean coupling)
   Standard scatterometer data: cannot get close to
    shore; insufficient resolution
   Synthetic aperture
    radar too infrequent
    and does not easily
    include wind direction
Objectives
 Long-term: To better resolve near-shore
  processes in the coastal ocean
 Medium-term: To provide validation for an ultra-
  high resolution (UHR) scatterometer product
  that has the potential to meet the needs of the
  coastal ocean community
 Short-term (this presentation):
     To evaluate the directional information provided by
      this UHR product
     To determine whether the UHR yields better near-
      shore coverage
QuikSCAT




                         http://winds.jpl.nasa.gov/images/seawindsqs_browse.jpg
 Dual pencil-beam Ku
  band radar
 Launched 1999
 Covers 90% of globe
  in 24 hrs
 Retrieves both speed
  and direction
Data
 October 2006
 Ultra-high resolution (UHR) retrievals with
  land contamination removal applied
 Standard QuikSCAT swath data (L2B): 25 km
  and 12.5 km
 Regional mesoscale meteorological model
  (MM5)
 Gulf of Maine Ocean Observing System
  (GoMOOS) and National Data Buoy Center
  (NDBC) buoys
Data: Buoys
Data: L2B Standard Swath
            12 km    25 km




 Speed


            12 km   25 km




Direction
Data: UHR and MM5 winds



= no buoy
report
Statistical Analysis
 Match based on finding all pixels within 10 km
  radius of each buoy, and taking average
 Residuals: scatterometer minus buoy (speed
  and direction)
 Number of buoy pairs
     1330 possible pairs: 725 for UHR, 557 for L2B 12.5
     km, and 171 for L2B 25 km.
   Organized according to:
     Buoy wind speed
     Cross-swath position
     Buoy station
   Mean, standard deviation of speed and
    direction residuals
Direction Fields




           Cross-
           swath
           position


                      = no buoy report
Ambiguity Re-selection
Latitudinal Slice   Taken at
                    41.5 N
http://www.weather.gov/forecasts/wfo/sectors/box.php


                                                       Coastal
                                                       Forecasting




http://www.weather.gov/forecasts/wfo/sectors/gyx.php
  Near-shore
  coverage




Percentages of pixels within:
Dist       UHR        12.5 km   25 km
50 km      58.3%      57.1%     52.7%
15 km      11.9%      10.0%     2.98%
5 km       0.54%      0.11%     0.01%
Data Quality
 Monthly summary:
 residuals vs. buoy
 station

Residual = scat wind – buoy wind
Conclusions
 Re-selection improves direction retrieval
  (compared to L2B, buoy, and model
  winds) in 51 out of 70 passes; and in
  part of swath for 13 additional passes.
 Near-shore coverage is improved within
  the 30-mile forecast area
 Summary of month’s residuals indicates
  UHR noisier than standard products, but
  similar in mean
Future Work
 Determine cause of directional errors(?)
 Run similar analyses of full data record (1999
  to present)
 Classify persistent flow patterns; determine
  where extra information is present in high-res
  retrievals
     For instance: sea breeze?
 Compare with HF currents
 Compare with SST
     Fronts
     Air-sea temp differences and stability
Questions?
Ambiguity Re-selection
Ambiguity Re-selection
Ambiguity Re-selection
Ambiguity Re-selection
Data Quality
  Residuals vs.
  buoy wind
  speed

Residual = scat wind – buoy wind
Monthly
summary:
Residuals vs.
cross-track
position
Outline
 Introduction
 Objectives
 Data
 Statistical Analysis
 Directional Errors
 Ambiguity Re-selection
 Near-shore Coverage
Data: UHR and MM5 winds