# Presentation: 376441

## High Quality Wind Retrievals for Hurricanes Using the SeaWinds Scatterometer

- W. Linwood Jones and Ian Adams
- Central Florida Remote Sensing Lab
- Univ. of Central FL

## Presentation Outline

- Hurricane Wind Vector Retrieval Issues
- CFRSL Hurricane Retrieval Algorithm
- QRad Rain Rate Algorithm
- Isabel and Fabian Results
- Conclusion

## Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

- Wind retrievals not tuned for high wind speeds
- Geophysical Model Function developed for wind speeds < 20 m/s
- CFRSL Approach
- Tropical Cyclone GMF tuned for retrieving high wind speeds
- Blended UMASS aircraft scat measurements and NSCAT GMF

## Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

- Egg spatial resolution @ 25 km sampling is too coarse
- CFRSL Approach
- Uses gridded “slice sigma-o” @ 12.5 Km sampling

## 25 km resolution using “eggs”

**50 km**

**25 km**

- Longitude

- Latitude

## Range gated “slices” from “egg”

- 6 km

- 30 km

- 12.5 km

- 25 km

## Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

- Rain has negative effects on wind measurements
- Rain attenuation lowers retrieved wind speeds
- Volume scattering increases retrieved wind speeds and alters directional signatures
- Rain “splash” increases retrieved wind speeds and changes anisotropic ocean surface features
- MUDDH performance in hurricanes is poor

## Issues with L2B Wind Vector Retrievalfor Extreme Wind Events

- Rain has negative effects on wind measurements
- CFRSL Approach
- Simultaneous rain measurement using QRad
- Rain attenuation and volume backscatter correction provided
- Rain splash effect included in GMF
- Rain Quality Flags Provided

## CFRSL Hurricane Retrieval Algorithm

- “Slice” sigma-0’s for improved spatial resolution - 12.5 km
- Sigma-0 minimum eye location
- Wind speed retrieved from individual sigma-0 (assumed spiral wind directions)
- Rain inferred using QRad rain rate algorithm
- Sigma-0 corrections from atmospheric transmissivity and rain volume backscatter
- Flag pixels that correspond to high rain attenuation

## QRad Algorithm Block Diagram

## Hurricane Eye Location

- Based upon
- Average of
- “4-flavor”
- Sigma-0’s
- 12.5 km
- sampling

- Longitude

- Latitude

## QRad/SRad Rain Algorithm

- Look at noise channel of scatterometer
- Subtract echo channel
- Calibrate radiometric temperature vs. TMI
- Train brightness temperature/rain rate relationship via TMI
- Coincident with scatterometer measurement

## QRad Integ. Rain Rate Product

- Improved CFRSL rain retrieval algorithm provides earth-gridded 50 km data product
- Instantaneous integrated rain rates > 2.4 km*mm/hr
- Resampled to 12.5 km wind vector grid

## QRad – TRMM 2A12 Instantaneous 

- Rain Rate

## QRad – TRMM 3B42RT HQ Instantaneous 

- QRad – TRMM 3B42RT HQ Instantaneous
- Collocated Low Rain event

- QRad

- TMI

## QRad – TRMM 3B42RT HQ Instantaneous 

- QRad – TRMM 3B42RT HQ Instantaneous
- Collocated Moderate Rain event

- QRad

- TMI

## QRad – TRMM 3B42RT HQ Instantaneous 

- QRad – TRMM 3B42RT HQ Instantaneous
- Collocated High Rain Event

- QRad

- TMI

## QRad (CFRSL) & TMI Integrated Rain Rates for Simultaneous Events

## AMSR vs. SRad Path Attenuation, Horizontal Polarization

- 102

- AMSR Attenuation

- SRad Attenuation

## 2003 Hurricane Results

## QuikSCAT Rev. 22055, Sept 13, 2003 22:04 Z 

- QuikSCAT Rev. 22055, Sept 13, 2003 22:04 Z

- (m/sec)

## SeaWinds Rev. 03927, Sept 15, 2003 15:40 Z 

- (m/sec)

- SeaWinds Rev. 03927, Sept 15, 2003 15:40 Z

## QuikSCAT Rev. 22084, Sept 15, 2003 22:52 Z 

- CFRSL Wind Retrieval

- SRad Rain Rate

- (mm/hr)

- HRD Wind Field, Time Interpolated

- (m/sec)

- QuikSCAT Rev. 22084, Sept 15, 2003 22:52 Z

## SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z 

- HRD Wind Field 01:30 Z

- SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z

- CFRSL Wind Retrieval

- SRad Rain Rate

- (mm/hr)

- (m/sec)

## SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z 

- HRD Modeled Wind Speed (m/s)

- CFRSL Wind Speed (m/s)

- HRD Modeled Wind Speed (m/s)

- JPL Wind Speed (m/s)

- SeaWinds Rev. 03934, Sept 16, 2003 02:52 Z

- JPL Wind Field

- CFRSL Wind Retrieval

## QuikSCAT vs. H* Wind Analysis

## SeaWinds vs. HRD Model

## CFRSL AlgorithmComposite Wind Speeds

- CFRSL AlgorithmComposite Wind Speeds

## Conclusion

- Ready to test current algorithm in operational environment
- Acceptable estimates of high rain rates inside storm conditions
- Reasonable wind speed retrievals up to
-    40 - 45 m/s
- Work must be done to improve model function and rain backscatter and attenuation estimates
- Will utilize UMass IWRAP and SFMR data set
- Have simultaneous AMSR and SRad for the 2003 hurricane season

## Backup Slides

## Error contribution of spiral direction