Status of improving the use of modis and avhrr polar winds in the gdas gfs
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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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Status of improving the use of modis and avhrr polar winds in the gdas gfs

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


Status of improving the use of modis and avhrr polar winds in the gdas gfs

Outline

  • Polar Winds product: MODIS and AVHRR

  • Current QC method

  • New approach

  • Forecast impact

  • Verification at 1800 UTC


Satellite derived polar winds

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.


Modis polar winds qc current thinning criteria

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


New approach

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)


  • Polar winds qc candidate thinning criteria

    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


    Lnvd threshold

    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


    Log normalized vector departure

    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


    Current qc vs lnvd 3 ms 1

    Current QC vs. LNVD3 ms-1

    Current

    LNVD

    Opposite Direction!

    • Purple dots represent the end point of vectors that will be retained


    Current qc vs lnvd 60 ms 1

    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


    Experiments

    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)


    Experiments1

    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


  • Modis northern hemisphere forecast impact 500 hpa acc heights

    MODIS: Northern HemisphereForecast Impact: 500 hPa ACC Heights

    • First season:10 September to 24 October 2012 (45 days)

    • Neutral Impact

    LNVD (red) Control (black)


    Modis southern hemisphere forecast impact 500 hpa acc heights

    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)


    Modis northern hemisphere forecast impact 500 hpa acc heights1

    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)


    Modis southern hemisphere forecast impact 500 hpa acc heights1

    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)


    Avhrr northern hemisphere forecast impact 500 hpa acc heights

    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)


    Avhrr southern hemisphere forecast impact 500 hpa acc heights

    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)


    Different verification time

    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)


  • 00 utc verification northern hemisphere 500 hpa height acc

    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


    18 utc verification northern hemisphere 500 hpa height acc

    18 UTC VerificationNorthern Hemisphere500 hPa Height ACC

    Red: LNVD

    Experiment

    Blue:

    Control

    Generally a neutral impact (Experiment slightly better)


    Wind rmse change global 00 utc vs 18 utc

    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


    Summary

    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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