1 Airborne Measurements of Ocean Backscatter Work In Progress by D. Esteban, Z. Jelenak, T. Mavor, P. Chang, NOAA/NESDIS/ORA D. Esteban, Z. Jelenak, T. Mavor, P. Chang, NOAA/NESDIS/ORA J. Carswell, Remote Sensing Solutions R. Contreras, S. Frasier, UMass – Amherst P. Black & F. Marks, NOAA/HRD Acknowledgements: NOAA/AOC, ONR, NASA

2 Outline IWRAP sampling technique Ocean backscatter: –High-wind GMF for QuikSCAT –Implementation and validation Rain processes in tropical cyclones: –Rainfall rate estimation –DSD parameters Impact on rain on ocean backscatter

3 IWRAP Measurement Technique Reflectivity and Doppler profiles – four beams, two frequencies: C/Ku High-resolution surface (ocean) and volume (rain) backscatter IWRAP Products: Rainfall rates and ocean surface wind field. 3D wind components of the boundary layer Range Resolution: 15, 30, 60 & 120 m Conical Scan (60 RPM)

4 Ocean NRCS Saturation

5 IWRAP GMF for QuikSCAT Derived at the QuickSCAT incidence angles (46 deg HH pol and 54 deg VV pol) VVHH

6 IWRAP high-wind GMF for QuikSCAT The wind vector retrieval becomes more complicated VVHH

7 IWRAP high-wind GMF for QuikSCAT Hurricane Isabel September 12 th, x12.5 Km resolution product QuikSCAT GMF IWRAP GMF

8 IWRAP high-wind GMF for QuikSCAT

9 Outline IWRAP sampling technique Ocean backscatter: –High-wind GMF for QuikSCAT –Implementation and validation Rain processes in tropical cyclones: –Rainfall rate estimation –DSD parameters Impact on rain on ocean backscatter

10 IWRAP Z vs. SFMR R r estimates Observations from 4 flights through Hurricane Isabel (2003) No single Z-R relationship !

11 IWRAP K S vs. SFMR R r estimates Observations from 4 flights through Hurricane Isabel (2003) Derived model :

12 Products: Rainfall rate estimation September 12 th, 2003 September 13 th, 2003 UTC Time hh:mm:ss

13 Drop Size Distributions Drop Size Distributions, N(D): (Rayleigh scattering) Characterization of N(D): –1-parameter DSD (e.g. M-P): –2-parameter DSD: –3-parameter DSD:

14 Two-parameter DSD We need two independent measurements:

15 The median mass diameter can be derived by: Two-parameter DSD Broader D 0 than the 1-parameter DSD

16 Outline IWRAP sampling technique Ocean backscatter: –High-wind GMF for QuikSCAT –Implementation and validation Rain processes in tropical cyclones: –Rainfall rate estimation –DSD parameters Impact on rain on ocean backscatter

17 Rain impact on ocean backscatter New, raw-data capabilities enable to differentiate rain and ocean contributions Doppler spectrums in the presence of light rain at Ku-band 40 deg incidence rain nadir ocean rain nadir ocean rain ocean h=510 m h=210 m h=120 m h=90 m h=30 m rain

18 Rain impact on ocean backscatter Azimuthal response 0 deg 30 deg 60 deg 90 deg 120 deg 150 deg h=510 m h= 30 m rain ocean

19 Accomplishments IWRAP provides a UNIQUE opportunity to better address some of the issues with satellite-based wind scatterometry: –Developed high-wind GMFs at C- and Ku-bands: Application to QuikSCAT wind vector retrieval. Currently implemented in parallel for near real-time, 25 and 12.5-km resolution. Validation in process. –Characterized rain processes from differential attenuation at C/Ku: Derived attenuation models for rainfall rate estimation Derived 1- and 2-parameter DSD –Looking at the impact of rain on the ocean backscatter response through spectral techniques

20 Dani Esteban: Paul Chang: Jim Carswell: Steve Frasier: Contacts