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Masanori Konda (Kyoto University/JAMSTEC IORGC) Akira Shibata (JAXA/EORC)

Correction of the Relative Wind Direction Effect on the AMSR Wind Speed and Its Impact on Estimating the Turbulent Heat Flux. Masanori Konda (Kyoto University/JAMSTEC IORGC) Akira Shibata (JAXA/EORC). Outline. Wind speed retrieval under the relative wind direction dependence (AMSR, AMSE)

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Masanori Konda (Kyoto University/JAMSTEC IORGC) Akira Shibata (JAXA/EORC)

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  1. Correction of the Relative Wind Direction Effect on the AMSR Wind Speed and Its Impact on Estimating the Turbulent Heat Flux Masanori Konda (Kyoto University/JAMSTEC IORGC) Akira Shibata (JAXA/EORC)

  2. Outline • Wind speed retrieval under the relative wind direction dependence (AMSR, AMSE) • Application to AMSR wind • Application to AMSR-E wind • Estimation of the instantaneous latent heat flux by using AMSR products • Comparison with the in situ measurements (TAO, KEO, JKEO) • JKEO and KEO surface measurements across the Kuroshio Extension.

  3. The relative wind direction effect on the brightness temperature • The incident angle is determined according to the pilot study of Stogryn (1967). • The angle between the sensor azimuth and the in-situ wind • Inhomogeneous change of the sea surface caused by the ocean wind affects the brightness temperature (Wentz 1992, Yueh et al.1999, Meissner and Wentz 2002 etc., Konda and Shibata, 2004) • the AMSR observation collocated with SeaWinds wvc • Correction of the relative wind effect without collocation of the SeaWinds (for the AMSR-E) f = 0, when AMSR is looking downwind

  4. PS36 (Partial shift of of the h-pol caused by wind) (Konda and Shibata 2004, GRL) PS36T(SST, IWV, CLW, SSWS, RWD)

  5. Application to AMSR-E data • Look-up table established by AMSR-SeaWinds collocations. • PS36= PS36T( SST , IWV , CLW , U6 , RWD ) These should be known from AMSR-E • Another proxy for the wind speed • Correlation with the SSWS (worse than AMSR SSWS) • Less sensitive to the RWD Obtainable from the level 2 data U6 and SeaWinds

  6. look-up table for AMSR-E • PS36 = PS36T(SST,IWV,CLW, U6, RWD) • PS36TR=PS36T(RWD)|SST,IWV,CLW,U6 Obtain from AMSR-E U6= 2-3m/s U6= 6-7m/s U6= 9-10m/s (SST, IWV, CLW) = ( 5-7C, 4-5mm, 0-0.02 Kg/m2) typical in the cold climate condition

  7. Correction of the RWD dependence (AMSR wind) Wind speed Red: uncorrected Black: corrected Cold condition Tropical condition

  8. Application to the AMSR-E wind • Collocation with SeaWinds on QuikSCAT • (SST, IWV, CLW) = ( 5-7 oC, 3-6 mm, 0-0.02 Kg/m2)

  9. Correction summary

  10. Impact of the RWD correction on the estimation of the latent heat flux difference between the latent heat flux with and without the RWD correction winds RMS=11.1 W/m2 RMS=28.0 W/m2 Accurate retrieval is needed.

  11. Obtaining the snapshot turbulent (latent) heat flux by AMSR (AMSR-E)

  12. Simulated impact of the time-lagged observation on the latent heat flux, using TAO (in situ) measurement The difference should be ambiguity rather than error Time-lagged latent heat flux 1.3 (44.9) W/m2 6-10 (AM/PM) average

  13. If we obtain individual parameters from the other satellite sensors (time-lagged measurement of latent heat flux) 48.8 (86.4) W/m2 AVHRR-SST QuikSCAT wind 10:00(AM/PM) 6:30 (AM/PM) 6-10 (AM/PM) average 10:30 (AM/PM) AMSR IWV => Liu and Niiler (1986)

  14. Instantaneous observation of the latent heat flux - summary - Ambiguity brought by the time-lag observation.

  15. Comparison with in situ observationKEO (Kuroshio Extension Observatory) and JKEO • Under the mid-latitude climate system • Twin measurement across the Kuroshio Extension SST front. • Under the active synoptic scale phenomena (seasonal wind, storm track, Typhoon etc.) Color: SST, Contour: NNR latent heat flux • JKEO (2007,2- 2008,2) => K-triton (2008, 2 -) • Northern side across the Kuroshio extension • Real time data will be accessed via JAMSTEC home page • KEO site: http://www.pmel.noaa.gov/keo/index.html • JKEO site : http://www.jamstec.go.jp/iorgc/ocorp/ktsfg/data/jkeo/

  16. More validation is needed in the mid-latitude RMSE=2.3 m/s RMSE=1.1 m/s Pixels are within 25km, 60 minutes. KEO wind : every 10 minutes JKEO wind: daily average

  17. summary • The method to correct the RWD dependence of the AMSR-derived SSWS (Konda and Shibata, 2004, Konda et al. 2006) is applied to AMSR-E wind. • AMSR-E SSWS in the mid latitude (KEO and JKEO sites) needs more validation or improvement of the algorithm. • Multi-parameters measurement by AMSR and AMSR-E has a merit of obtaining the snapshot latent heat flux (~50 W/m2). • KEO and JKEO buoys provides in situ boundary layer parameters in the Kuroshio Extension region. • KEO : http://www.pmel.noaa.gov/keo/index.htmlJKEO: http://www.jamstec.go.jp/iorgc/ocorp/ktsfg/data/jkeo/

  18. The AMSR-E wind (standard product level 2) and the KEO wind 2004,Jun. –Dec. AMSR-E level 2 wind 6m/s RMS=2.14 m/s AMSR-E L2B wind -6m/s Relative wind direction The RWD effect should be hidden because of the large error. (more effort is needed). KEO wind Pixels are within 10km, 10 minutes. KEO wind : every 10 minutes

  19. The AMSR-E wind (standard product level 2) and the KEO wind 2004,Jun. – Dec. Wind after the correction 6m/s RMS=2.14 m/s AMSR-E L2B wind -6m/s Relative wind direction The RWD effect should be hidden because of the large error. (more effort is needed). KEO wind Pixels are within 10km, 10 minutes. KEO wind : every 10 minutes

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