1. Scatterometers at KNMI; Towards Increased Resolution Ad.Stoffelen@KNMI.nl Hans Bonekamp Marcos Portabella http://www.knmi.nl/scatterometer Isabel

2. 2 Miami Workshop 8-10 Feb ‘05 Overview  Scatterometer winds contain mesoscale detail not captured by NWP fields, but also noise  Mesoscale information is useful for nowcasting  MSS: an effective way of controling the noise  Spatial analysis in progress

3. 3 Miami Workshop 8-10 Feb ‘05 Spectral tail  Spectral response is used in engineering for design of noise properties Energy density Ideal Noisy Truncated Wave number  Being used now to increase SeaWinds resolution at KNMI

4. 4 Miami Workshop 8-10 Feb ‘05 Bad rainy case  Nadir noisy

5. 5 Miami Workshop 8-10 Feb ‘05 Broad Wind Direction Minima Probability of  Wind direction (  ) Local minima  Local minima do not represent solution P Solution bands

6. 6 Miami Workshop 8-10 Feb ‘05 A wide range of probable solutions exists in nadir (of 144 solutions per WVC) Locally, 100-km product is pretty Unique (P threshold is 10 -7 ) Broad Minima

7. 7 Miami Workshop 8-10 Feb ‘05 Spatial filter:  Mass conservation  Continuity equation  0 U = 0  Vertical motions < horizontal motion  Little divergence  Mostly rotation (extratropics) Meteorological balance (2D-VAR)

8. 8 Miami Workshop 8-10 Feb ‘05 100 km Multiple Solution Scheme 1.Full use of solution probability info 2.Meteorological balance in Ambiguity Removal (2D-VAR) (Portabella&Stoffelen, 2003)  Smooth solution exists @100 km

9. 9 Miami Workshop 8-10 Feb ‘05 Standard scheme: < 4 solutions  Erratic at low wind speeds

10. 10 Miami Workshop 8-10 Feb ‘05 Multiple Solution Scheme  Smooth representation  Mesoscale detail kept

11. 11 Miami Workshop 8-10 Feb ‘05  ECMWF Position error ECMWF First Guess

12. 12 Miami Workshop 8-10 Feb ‘05 General MSS performance @100 km Mean vector RMS difference with ECMWF FGAT (m/s)  MSS better than 4-solution standard, in particular at nadir  NCEP background for 2DVAR much worse

13. 13 Miami Workshop 8-10 Feb ‘05 NOAA MSS @ 25 km Improved cold front Better Around rain 50 km Plots !

14. 14 Miami Workshop 8-10 Feb ‘05 NOAA MSS @ 25 km Improved inflow Better Around rain

15. 15 Miami Workshop 8-10 Feb ‘05 MSS @ 25 km NOAA Improved inflow NCEP

16. 16 Miami Workshop 8-10 Feb ‘05 Summary - The use of more wind retrieval information in MSS allows consistent mesoscale features in the 25-km product - A balanced spatial filter such as 2D-VAR is effective in removing noise and keeping meteorology, direction or vector uniformity constraints are less effective - At 100-km the background wind used for ambiguity removal appears irrelevant, but this needs checking at 25 km - The spectral behaviour of 2D-Var at 25-km needs to be evaluated - Verification against buoys is underway

17. 17 Miami Workshop 8-10 Feb ‘05 Further References For scatterometer-related papers, documentation, and wind products of the SAFs please refer to http://www.knmi.nl/scatterometer We look forward to sharing - Our scatterometer processing software - Our ERS and QuikScat products - Our new wind stress products - Our experience We fund visiting scientists E-mail: scat@KNMI.nl

18. 18 Miami Workshop 8-10 Feb ‘05 DIRTH (NOAA product) JPL’s Direction Interval Retrieval Threshold Nudging DIRTH TN removes noise in 25-km product, but at some expense  Unnormalised notion of P (WVC and speed dependence)  P segments exclude probable solutions (T=0.8; 0.2 left out)  Medium filter ignores P within segment  No meteorological balance constraints DIRTH results in  Very smooth fields (> 100 km)  Loss of meteorological detail  KNMI proposes Multiple Solution Scheme

19. 19 Miami Workshop 8-10 Feb ‘05 Scatterometer Data Processor Observations Inversion Ambiguity Removal Wind Field OUTPUT Ocean Surface Radar Backscatter Observations Inversion Ambiguity Removal Quality Control Pre- Process Wind Field INPUT OUTPUT Quality Monitor

20. 20 Miami Workshop 8-10 Feb ‘05 Ambiguity Probability Quadratic inner loop approximation? IFS experiments from KNMI + some visits

21. 21 Miami Workshop 8-10 Feb ‘05 http://www.knmi.nl/scatterometer QuikSCAT

22. 22 Miami Workshop 8-10 Feb ‘05 NWP Impact @ 100 km Storm near HIRLAM misses wave; SeaWinds should be beneficial! 29 10 2002

23. 23 Miami Workshop 8-10 Feb ‘05 Satellite Application Facilities Scatterometer sea surface wind R&D Quality control, rain and ice screening Spatial averaging (100 km  25 km) Inversion: Computation of wind solutions and associated probabilities from measurement information Determination of information content; Observation operator Ambiguity removal (spatial filter to determine unique field) Active monitoring and control (of instrument and processing) Web site (visualisation) and product distribution  Product enhancement  Preparation for ASCAT wind production (METOP; 2006)

24. 24 Miami Workshop 8-10 Feb ‘05 Detail in 100-km product KNMI 100km

25. 25 Miami Workshop 8-10 Feb ‘05 Product Verification with ECMWF Winds SDKNMINOAA Speed1.311.64 Direction13.5814.58 U1.601.96 V1.581.80 Comparison for a set of triple KNMI-NOAA-ECMWF points  KNMI 100-km product better for NWP assimilation than NOAA  NOAA wind speed score relatively bad due to wind direction spatial filter  KNMI rejects less high wind points (Portabella &, 2000)