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Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Rain/Wind Backscatter Model Model for measured backscatterModel for measured backscatter
Radar signal scattered by falling Radar signal scattered by falling droplets droplets
Surface signal attenuated by Surface signal attenuated by atmospheric rainatmospheric rain
Surface wind-induced Surface wind-induced backscatter perturbed by rain backscatter perturbed by rain striking the waterstriking the water
Model derived from colocated Model derived from colocated TRMM PR and QuikSCAT dataTRMM PR and QuikSCAT data
Rain affects ~4% of SeaWinds dataRain affects ~4% of SeaWinds data oM
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Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Simultaneous Wind/Rain Retrieval
Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Wind Rain Regimes
Regime 1: rain dominates wind backscatter – poor quality wind estimates Regime 1: rain dominates wind backscatter – poor quality wind estimates (10% of rain (10% of rain cases*)cases*)
Regime 2: both wind and rain important – can retrieve wind and rain rate Regime 2: both wind and rain important – can retrieve wind and rain rate (34% of rain (34% of rain cases*)cases*)
Regime 3: rain effects insignificant – wind estimates unaffected by rainRegime 3: rain effects insignificant – wind estimates unaffected by rain (56% of rain (56% of rain cases*)cases*)
Note: globally, only about 4% of all QuikSCAT data effected by rain Note: globally, only about 4% of all QuikSCAT data effected by rain
* From collocated TRMM PR and QuikSCAT data in tropics* From collocated TRMM PR and QuikSCAT data in tropics
)()(,,,,, RRuMRu effo
)(Reff incorporates surface rain perturbation, atmospheric rain scattering, and attenuationincorporates surface rain perturbation, atmospheric rain scattering, and attenuation
- Empirical function of rain rate derived from collocated QuikSCAT and TRMM PR- Empirical function of rain rate derived from collocated QuikSCAT and TRMM PR
Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Scatterometer Rain Retrieval Validation
Bias can be estimated and corrected for
Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Rain Estimate Validation
QuikSCAT-derived rain rates vs TMI-derived rain ratesQuikSCAT-derived rain rates vs TMI-derived rain rates
Brigham Young UniversityBrigham Young University
DGL Dec 03DGL Dec 03
Floyd (rev 1201, 11 Sept 1999)