1. 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 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 QC Current Thinning criteria qcU = qcV = 7 ms -1 (O-B) U > qcU OR (O-B) V > qcV Within 50 hPa of the tropopause Within 200 hPa of the surface, if over land 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 QC Candidate Thinning criteria Discards winds when Log Normalized Vector Departure (LNVD) exceeds a threshold SQRT ( (U o -U b ) 2 + ( V o – V b ) 2 ) / log(ObsSpd) > Threshold Within 50 hPa of the tropopause Within 200 hPa of the surface, if over land

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 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 LNVD Threshold = 3

9. Current QC vs. LNVD 3 ms -1 Purple dots represent the end point of vectors that will be retained Current LNVD Opposite Direction!

10. Current QC vs. LNVD 60 ms -1 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 Current LNVD

11. Experiments Running r29119 hybrid GDAS/GFS on S4 Verify 00 UTC forecast run Two Seasons 1.1 September to 25 October 2012 (own analysis) 2.1 April to 31 May 2012 (consensus analysis)

12. Experiments 1 September to 25 October 2012 1.Control Current QC with operational data 2.MODIS LNVD => VecDiff / Log(Obs_spd) < 3 3.AVHRR (NOAA-15, 16, 18, 19, Metop-A) a)AVHRR replaces MODIS 1 April to 31 May 2012 1.Control Current QC with operational data 2.MODIS LNVD => VecDiff / Log(Obs_spd) < 3

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

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

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

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

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

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

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 Verification Northern Hemisphere 500 hPa Height ACC Generally a neutral impact (Control slightly better) Experiment dropout on Day 1; Control dropout on Day 4 Red: LNVD Experiment Blue: Control

21. 18 UTC Verification Northern Hemisphere 500 hPa Height ACC Generally a neutral impact (Experiment slightly better) Red: LNVD Experiment Blue: Control

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

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