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Atelier Moment Cinetique Paris 26 Novembre 2012 Les Vents de Surface Diffusiométriques 1992 2020 929496980002040608101214161820 ERS-1 ERS-2 ADEOS-1 QuikSCAT ADEOS-2 MetopA OSCAT2 HY-2A MetopB CFOSAT HY-2B Meteor-M3
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Atelier Moment Cinetique Paris 26 Novembre 2012 Les Vents de Surface Diffusiométriques Bentamy, A., D. Croize-Fillon, and C. Perigaud, 2008: Characterization of ASCAT measurements based on buoy and QuikSCAT wind vector observations, Ocean Sci., 4, 265–274. Bentamy, A.; D. Croize-Fillon, P. Queffeulou; C. Liu, H. Roquet, 2009: Evaluation of high-resolution surface wind products at global and regional scales. Journal of Operational Oceanography, vol. 2, 15-27(13). Bentamy, A., S. A. Grodsky, J. A. Carton, D. Croizé-Fillon, and B. Chapron, 2012: Matching ASCAT and QuikSCAT Winds, J. Geoph. Res., doi:10.1029/2011JC007479 Grodsky S. A., V. N. Kudryavtsev, A. Bentamy, J. A. Carton, and B. Chapron, 2012: Does direct impact of SST on short wind waves matter for scatterometry?, Geophys. Res. Letters, doi:10.1029/2012GL052091
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Atelier Moment Cinetique Paris 26 Novembre 2012 The main scatterometer measurements are the backscatter coefficients calculated as a ratio between the emitted power P e and the received one P r : : the wavelength, G the antenna gain, A the radar footprint, R the distance between the sensor and the reached target. Scatterometers are active microwave sensors: they send out a signal and measure how much of that signal returns after interacting with the target. Microwaves are Bragg scattered by short water waves; the fraction of energy returned to the satellite (backscatter) is a function of wind speed and wind direction. Scatterometer measurement
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Scatterometer Calibration Retrieving Surface Winds from Backscatter Coefficient Measurements is not Trivial Atelier Moment Cinetique Paris 26 Novembre 2012 Calibration Procedure: Determination of Geophysical Model Function (GMF): ° = f(U, , , P,fc, ….)
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PORSEC 2012 Kochi Tutorial GMF : Scatterometer Geophysical Relationships Buoy Wind Speed Range 8m/s
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PORSEC 2012 Kochi Tutorial GMF : Scatterometer Geophysical Relationships Buoy Wind Speed Range 3m/s
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PORSEC 2012 Kochi Tutorial GMF : Scatterometer Geophysical Relationships Buoy Wind Speed Range 12m/s
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Atelier Moment Cinetique Paris 26 Novembre 2012 ASCAT / QuikSCAT ( Bentamy et al, 2011 ) Study Period: April 2007 – November 2009 Focus : November 2008 – November 2009 ASCAT Data Source: OSI SAF / KNMI Products: L1b & L2b 25 & L2b 12.5 GMF : CMOD5 and CMOD5n Wind retrieval: Selected solution Data selection: All WVC Wind Speed : 0 – 50m/s Wind direction : 0° – 360° Quality flags QuikSCAT / QuikSCAT V3 Data Source: PODAAC / JPL Products: L1b & L2b 25 / L2b 12.5 GMF : QSCAT-1/F13 / QuikSCAT (Ku2011) Wind retrieval: Selected solution Data selection: All WVC Wind Speed : 0 – 50m/s Wind direction : 0° – 360° Quality flags / New Rain flags
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Atelier Moment Cinetique Paris 26 Novembre 2012 Local Assessment for ASCAT/QSCAT Collocated Data Comparisons with NDBC buoy hourly measurements
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Atelier Moment Cinetique Paris 26 Novembre 2012 Global Comparisons Bias (top), STD (middle), and Correlation (bottom) of collocated QuikScat and ASCAT winds.
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Analysis of ASCAT and QSCAT Differences Atelier Moment Cinetique Paris 26 Novembre 2012 Wind speed difference. QuikSCAT rain flag and MRP<0.05 are applied Spatial distribution of the time mean Wind speed difference after applying the correction function Histogram of wind speed difference before (gray bar) and after (empty bar) applying of dW
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Mean Difference of Wind Speeds: QSCAT / ASCAT / ECMWF / ERA Interim Atelier Moment Cinetique Paris 26 Novembre 2012 QSCAT ASCAT ECMWFERAI
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Mean Difference of Wind Components : QSCAT / ASCAT / ECMWF Atelier Moment Cinetique Paris 26 Novembre 2012 | QSCAT | - | ASCAT | | QSCAT | - | ECMWF | | ASCAT | - | ECMWF | ZonalMeridional
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Mean Difference of Wind Components: QSCAT / ASCAT / ERA Interim Atelier Moment Cinetique Paris 26 Novembre 2012 |QSCAT| - | ASCAT | | QSCAT | - | ERAI | | ASCAT | - | ERAI | ZonalMeridional
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Zonal Means of Wind Components Within 3 degree of 140°W Atelier Moment Cinetique Paris 26 Novembre 2012
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16 High Wind Field Spatial and Temporal Resolution QuikSCAT SSMI AMSR-E TMI Jason METOP Objectives Estimation of high spatial and temporal resolution of surface wind fields (wind vector and wind stress) using ECMWF Numerical Weather analysis outputs with high remotely sensed surface parameters. 6-hourly, 0.25° x 0.25° Set-up and carry-out a demonstration experiment, to produce in near real-time merged wind fields : 6-hourly, 0.25° x 0.25° Assess the quality of derived blended wind fields at near shore and offshore areas. E.U. MyOcean-1/2 Projects Operational ECMWF Analysis Atelier Moment Cinetique Paris 26 Novembre 2012
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17 Objective Method Objective Method : External Drift Wind Observations (U) are from NRT Scatterometer and SSM/I External Data (S) are from ECMWF analysis. Assumption : E(U(X,t)) = a + b*S(X,t) The space and time correlation is parameterized by Atelier Moment Cinetique Paris 26 Novembre 2012
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AMS Conference 20 - 24 August 2007 Portland 18 Blended Surface Wind Fields Method : Objective OI (Bentamy et al, 2007; 2009) Results : 6-hourly global wind vector 0.25°×0.25° May 4 th 2008. 00h:00 May 4 th 2008. 06h:00 Atelier Moment Cinetique Paris 26 Novembre 2012
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Evaluation Versus QuikSCAT (off-line) Wind Observations January 2005 ( Bentamy et al, 2009 ) QuikSCAT – Blended BiasRms QuikSCAT – ECMWF BiasRms W U V
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