SVW Requirements WorkshopMiami, FL

5-7 June, 2006

Airborne Measurements of Ocean Backscatter

Daniel Esteban FernandezAcknowledgements: NOAA NESDIS Office Research & Applications

NOAA Aircraft Operations CenterUniversity of Massachusetts

SVW Requirements Workshop5-7 June, 2006, Miami

Outline

IWRAP– Description and measurement technique

Scatterometry Geophysical Model Functions (GMFs)– Methodology– Dual-band (C and Ku), dual-polarized (H and V)

GMFs from IWRAP measurements

SVW Requirements Workshop5-7 June, 2006, Miami

IWRAP Measurement Technique• Reflectivity and Doppler profiles – four beams, two frequencies

(C and Ku), two polarizations (H and V) – simultaneously.

• High-resolution surface and volume backscatter

Range Resolution: 15, 30, 60 & 120 m

Conical Scan(60 RPM)

Range Resolution: 15, 30, 60 & 120 m

Conical Scan(60 RPM)

Range Resolution: 15, 30, 60 & 120 m

SVW Requirements Workshop5-7 June, 2006, Miami

IWRAP Designed to Investigate…

Hurricane Katrina, August 28 th, 2005

SVW Requirements Workshop5-7 June, 2006, Miami

Summary of datasets Flown during 2002, 2003, 2004 and 2005 Hurricane seasons, and

the 2003 and 2005 Winter Storm experiments: 70 missions, including flights through hurricanes Gustav, Isidore, and Lili

(2002), Fabian and Isabel (2003), Frances and Ivan (2004), Ophelia and Rita (2005), as well as several TDs, TSs and extra-tropical storms.

Collected measurements of ocean surface winds up to 72 m/s and rain rates over 100 mm/hr, and boundary layer winds in excess of 100 m/s.

Several flights coincident with WindSAT and QuikSCAT passes.

Hundreds of GPS drop-sondes deployed.

Collocated radiometer (SFMR) brightness temperatures measurements providing surface wind speed and precipitation estimates.

SVW Requirements Workshop5-7 June, 2006, Miami

Work performed

• Obtained dual-polarized (H and V) C- and Ku-band model functions of ocean backscatter versus wind speed and direction:– Wind speed > 25 m/s in rain-free conditions.– C-band H polarization (full range).

• Compared against other models (CMOD4/5, NSCAT2, QSCAT1, etc.): – Shown a decreased sensitivity at high-winds.– Developed the model for the QuikSCAT incidence angles. – Implemented in a parallel NOAA/NESDIS/ORA NRT QuikSCAT

25-km and 12.5-km processor.

SVW Requirements Workshop5-7 June, 2006, Miami

High Winds Ku-band Model Function

log

log

25 25

SVW Requirements Workshop5-7 June, 2006, Miami

High Winds C-band Model Function

log

log

SVW Requirements Workshop5-7 June, 2006, Miami

Full-range C-band H pol. models

SVW Requirements Workshop5-7 June, 2006, Miami

A2/A0 versus wind speed

C-band VV

C-band HH

Ku-band VV

Ku-band HH

SVW Requirements Workshop5-7 June, 2006, Miami

C-band NRCS Azimuthal response

VV50 deg

HH49 deg

SVW Requirements Workshop5-7 June, 2006, Miami

Ku-band NRCS Azimuthal Response

VV48 deg

HH48 deg

SVW Requirements Workshop5-7 June, 2006, Miami

Conclusions C- and Ku-band mean ocean backscatter measurements show a

decreased sensitivity for wind speeds above ~45 m/s.

H-pol behaves similarly to V-pol for both C- and Ku-band at high wind speeds, but…

C-band H-pol at high incidence angles shows a much higher saturation point (not reached at 65 m/s).

C- and Ku-band A2/A0 measurements decrease to < 0.1 thus supporting the observed decreased sensitivity in wind direction as well.

Best bet to retrieve high winds (> 50 m/s) from scatterometry is C-band H-pol at high incidence angles.