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Status of improving the use of MODIS and AVHRR polar winds in the GDAS/GFS

Status of improving the use of MODIS and AVHRR polar winds in the GDAS/GFS. David Santek, Brett Hoover, Sharon Nebuda, James Jung Cooperative Institute for Meteorological Satellite Studies University of Wisconsin - Madison. 1 2th JCSDA Workshop on Satellite Data Assimilation NCWCP

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Status of improving the use of MODIS and AVHRR polar winds in the GDAS/GFS

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  1. Status of improving the use of MODISand AVHRR polar winds in the GDAS/GFS • David Santek, Brett Hoover, Sharon Nebuda, James Jung • Cooperative Institute for Meteorological Satellite Studies • University of Wisconsin - Madison 12th JCSDA Workshop on Satellite Data Assimilation NCWCP College Park, Maryland 23 May 2014

  2. Outline • Polar Winds product: MODIS and AVHRR • Current QC method • New approach • Forecast impact • Verification at 1800 UTC

  3. Satellite-derived Polar Winds Unlike geostationary satellites at lower latitudes, it is not be possible to obtain complete polar coverage at a snapshot in time with one or two polar-orbiters. Winds must be derived for areas that are covered by three successive orbits The gray area is the overlap between three orbits. Three overlapping Aqua MODIS passes, with WV and IR winds superimposed. The white wind barbs are above 400 hPa, cyan are 400 to 700 hPa, and yellow are below 700 hPa.

  4. MODIS Polar Winds QCCurrent Thinning criteria Within 50 hPa of the tropopause Within 200 hPa of the surface, if over land qcU = qcV = 7 ms-1 (O-B)U > qcU OR (O-B)V > qcV Special case qcU = qcV = (ObsSpd + 15)/3 (IR wind within 200 hPa of surface OR WV wind below 400 hPa) AND (GuessSpd +15)/3 < qcU

  5. New Approach • Goal: One method for screening all polar winds • MODIS, AVHRR, VIIRS • Wind speeds vary over 3 orders of magnitude (1, 10, 100 ms-1) • Normalize vector departure by Log of speed • Log Normalized Vector Departure (LNVD)

  6. Polar Winds QCCandidate Thinning criteria Within 50 hPa of the tropopause Within 200 hPa of the surface, if over land Discards winds when Log Normalized Vector Departure (LNVD)exceeds a threshold SQRT ( (Uo-Ub)2 + ( Vo – Vb)2 ) / log(ObsSpd) > Threshold

  7. LNVD Threshold • Discard winds LNVD > 3 • Compared to control: • Similar number of vectors discarded • Discard more slow winds • Retain more high speed winds 9 – 26 October 2012

  8. Log Normalized Vector Departure LNVD Threshold = 3 ObsSpd* Log(ObsSpd) VecDif ------ ----------- ---------- 3 1.1 3.3 10 2.3 6.9 50 3.9 11.7 100 4.6 13.8 *Speed in ms-1

  9. Current QC vs. LNVD3 ms-1 Current LNVD Opposite Direction! • Purple dots represent the end point of vectors that will be retained

  10. Current QC vs. LNVD60 ms-1 Current LNVD • Blue arrow represents the wind vector at 60 ms-1 • Purple dots represent the end point of vectors that will be retained • Purple vector is one possible AMV that would be retained

  11. Experiments • Running r29119 hybrid GDAS/GFS on S4 • Verify 00 UTC forecast run • Two Seasons • 1 September to 25 October 2012 (own analysis) • 1 April to 31 May 2012 (consensus analysis)

  12. Experiments • 1 September to 25 October 2012 • Control Current QC with operational data • MODIS LNVD => VecDiff / Log(Obs_spd) < 3 • AVHRR (NOAA-15, 16, 18, 19, Metop-A) • AVHRR replaces MODIS • 1 April to 31 May 2012 • Control Current QC with operational data • MODIS LNVD => VecDiff / Log(Obs_spd) < 3

  13. MODIS: Northern HemisphereForecast Impact: 500 hPa ACC Heights • First season:10 September to 24 October 2012 (45 days) • Neutral Impact LNVD (red) Control (black)

  14. MODIS: Southern HemisphereForecast Impact: 500 hPa ACC Heights • First Season:10 September to 24 October 2012 (45 days) • Significant impact at Day 4 and 5 Significant LNVD (red) Control (black)

  15. MODIS: Northern HemisphereForecast Impact: 500 hPa ACC Heights • Second Season:9 April to 16 May 24 2012 (38 days) • Neutral Impact LNVD (red) Control (black)

  16. MODIS: Southern HemisphereForecast Impact: 500 hPa ACC Heights • Second Season:9 April to 16 May 24 2012 (38 days) • Neutral Impact LNVD (red) Control (black)

  17. AVHRR: Northern HemisphereForecast Impact: 500 hPa ACC Heights • 10 September to 13 October 2012 (30 days) • Neutral Impact • Good news because AVHRR replaced MODIS AVHRR-only (red) MODIS-only (black)

  18. AVHRR: Southern HemisphereForecast Impact: 500 hPa ACC Heights • 10 September to 13 October 2012 (30 days) • Neutral Impact • Good news because AVHRR replaced MODIS AVHRR-only (red) MODIS-only (black)

  19. Different Verification Time • Forecast impact typically measured with 00 UTC model run • Most input data • What is AMV impact when radiosondes not available? • Examine impact for 18 UTC model run of MODIS LNVD Experiment • One-month period (23 Sep - 24 Oct 2012)

  20. 00 UTC VerificationNorthern Hemisphere500 hPa Height ACC Blue: Control Red: LNVD Experiment Generally a neutral impact (Control slightly better) Experiment dropout on Day 1; Control dropout on Day 4

  21. 18 UTC VerificationNorthern Hemisphere500 hPa Height ACC Red: LNVD Experiment Blue: Control Generally a neutral impact (Experiment slightly better)

  22. Wind RMSE ChangeGlobal: 00 UTC vs. 18 UTC 18 UTC 00 UTC Green: Reduce vector RMSE Red: Increase vector RMSE Note: Color scales are different

  23. Summary • Results are encouraging for using the LNVD quality control: Reject more slow winds; Accept more fast winds • AVHRR-only winds have a neutral forecast impact compared to MODIS-only winds: AVHRR, VIIRS are future • Forecast verification of MODIS polar winds with 18 UTC model run worth additional investigation • Working with Iliana Genkova to get code checked into NCEP SVN • This project ends on 31 May 2014 • NOAA: NA10NES4400011

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