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Application of AMSR wind speed algorithm for retrieving Windsat vector wind Akira Shibata JAXA

This presentation discusses the implementation of the AMSR wind speed algorithm for retrieving wind vectors from Windsat in the absence of SeaWinds on Quickscat data. The algorithm includes parameters such as S36, SST, atmospheric corrections, and relative wind direction determination. The retrieval process involves defining lines based on SST and 10H* values, calculating wind direction, and converting parameters to wind speed. While the algorithm performs well for strong winds, improvements are needed for moderate wind conditions. Issues with Windsat data, such as Tb calibration errors and spatial mismatches, are also highlighted.

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Application of AMSR wind speed algorithm for retrieving Windsat vector wind Akira Shibata JAXA

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  1. Application of AMSR wind speed algorithm for retrieving Windsat vector wind Akira Shibata JAXA AMSR-E meeting, at Huntsville, June 2-3, 2010

  2. Backgrounds • SeaWinds on Quickscat stopped its operation in November 2009. Then, quality data of wind vector from Windsat became more necessary for analysis of weather forecast. • AMSR wind speed algorithm is being applied for retrieving wind vector from Windsat.

  3. Parameter Definition AMSR s36 = (36H - (s × (36V – a) + b ) ) / fac parameters a ,b, s, fac depend on SST 10H* = AMSR_10H – atmos_effect_10H –calm_ocean_10H 10H* available within no-rainy area because of atmospheric correction using higher frequencies 23/36V Windsat Stokes parameters 18GHz 3rd/4th

  4. Determination of relative wind direction (AMSR case) - 6H* / s36 plane - cross (K) 16m/s up down 6H* 7m/s (K) s36 wdir positive = downwind wdir available for wind speed greater around 7m/s

  5. Conversion of s36 to wind speed (AMSR case) After s36 is transformed to cross-wind position K s36 m/s wind speed

  6. Stokes 3rd/4th parameter (Windsat case) 315 10<SST<15 270 135 225 90 relative wind direction 0/360 upwind 45

  7. Combination of stokes parameters and wdir wdir negative wdir positive

  8. Retrieval of wind vector for Windsat • Define six lines which form 3rd/4th planes, which are variable in SST and 10H* • Calculate relative wind direction by position of the nearest line, assisted by knowledge of wdir • Temporary, 10H* is used instead of s36 Only retrievable for wind speed larger than around 7m/s, and within no-rainy areas.

  9. Windsat 3rd/4th plane 10<SST<15 5<10H*<7 9<10H*<11 13<10H*<15 17<10H*<19

  10. Comparison of Windsat vector and GANAL (JMA) 12GMT Jan. 1, 2009

  11. Comparison of Windsat vector and GANAL (JMA) Jan. 1, 2009

  12. Comparison of Windsat vector and GANAL (JMA) Jan. 1, 2009

  13. Comparison of Windsat vector and GANAL (JMA) Jan. 1, 2009

  14. Status • Algorithm of retrieving wind direction seems to work well for strong wind, but it needs further works for middle wind. Windsat data problems • Due to possible Tb calibration error, s36 has anomalous values, which vary along orbits and monthly. • Scan bias errors existing, in particular for s36 • Mismatch of spatial locations of s36 and 10H*

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