Rain/Wind Backscatter Model

1. Rain/Wind Backscatter Model Rain affects ~4% of SeaWinds data • Model for measured backscatter • Radar signal scattered by falling droplets • Surface signal attenuated by atmospheric rain • Surface wind-induced backscatter perturbed by rain striking the water • Model derived from colocated TRMM PR and QuikSCAT data

2. Simultaneous Wind/Rain Retrieval

3. Wind Rain Regimes • incorporates surface rain perturbation, atmospheric rain scattering, and attenuation - Empirical function of rain rate derived from collocated QuikSCAT and TRMM PR • Regime 1: rain dominates wind backscatter – poor quality wind estimates (10% of rain cases*) • Regime 2: both wind and rain important – can retrieve wind and rain rate (34% of rain cases*) • Regime 3: rain effects insignificant – wind estimates unaffected by rain (56% of rain cases*) • Note: globally, only about 4% of all QuikSCAT data effected by rain * From collocated TRMM PR and QuikSCAT data in tropics

4. Wind/Rain Validation

5. Scatterometer Rain Retrieval Validation Bias can be estimated and corrected for

6. Rain Estimate Validation • QuikSCAT-derived rain rates vs TMI-derived rain rates

7. Storm Example

8. Floyd (rev 1201, 11 Sept 1999)

9. Typhoon (rev 1222, 12 Sept 1999)